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Sustained Load Performance of Adhesive Anchor Systems in Concrete

Permanent Link: http://ufdc.ufl.edu/UFE0044501/00001

Material Information

Title: Sustained Load Performance of Adhesive Anchor Systems in Concrete
Physical Description: 1 online resource (570 p.)
Language: english
Creator: Davis, Todd M
Publisher: University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: 2012

Subjects

Subjects / Keywords: adhesive -- anchor -- concrete -- creep -- sustained
Civil and Coastal Engineering -- Dissertations, Academic -- UF
Genre: Civil Engineering thesis, Ph.D.
bibliography   ( marcgt )
theses   ( marcgt )
government publication (state, provincial, terriorial, dependent)   ( marcgt )
born-digital   ( sobekcm )
Electronic Thesis or Dissertation

Notes

Abstract: Stemming from a tragic failure of an adhesive anchor system, this research project investigated the sustained load performance of adhesive anchors in concrete under different installation and in-service conditions. The literature review investigated the current state of art of adhesive anchors.  Extensive discussion was devoted to the behavior of adhesive anchors in concrete as well as the many factors that can affect their short-term and sustained load strength.  Existing standards and specifications for the testing, design, construction, and inspection of adhesive anchors were covered. Based on the results of the literature review and the experience of the research group, a triage was conducted on many parameters identified as possibly affecting the sustained load performance of adhesive anchors and the highest priority parameters were investigated in this project.  A stress versus time-to-failure approach was used to evaluate sensitivity of three ICC-ES AC 308 approved adhesive anchor systems.  Of the various parameters investigated, only elevated in-service temperature and manufacturer’s cure time was shown to exhibit adverse effects on sustained loads more than that predicted by short-term tests of fully cured adhesive over a reasonable structure lifetime of 75 years. In a related study, various tests were conducted on the adhesive alone (time-temperature superposition, time-stress superposition, and dogbone tensile tests).  The results of that study were used to investigate the existence of a correlation with long-term anchor pullout testing in concrete.  No consistent correlations were detected for the adhesives in the study. Tests were also conducted on the effect of early-age concrete on adhesive anchor bond strength.  On the basis of confined test bond-strength alone, adhesive A (vinyl ester) did not show any significant increase after 14 days (102% of 28 day strength at 14 days), and adhesive B and C (epoxies) did not show any significant increase after 7 days (104% and 93% of 28 days strength at 7 days respectively). The results of this research were used to draft recommended standards and specifications for AASHTO pertaining to testing, design, construction, and inspection of adhesive anchors in concrete for transportation structures.  These draft standards were not included in this dissertation.
General Note: In the series University of Florida Digital Collections.
General Note: Includes vita.
Bibliography: Includes bibliographical references.
Source of Description: Description based on online resource; title from PDF title page.
Source of Description: This bibliographic record is available under the Creative Commons CC0 public domain dedication. The University of Florida Libraries, as creator of this bibliographic record, has waived all rights to it worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law.
Statement of Responsibility: by Todd M Davis.
Thesis: Thesis (Ph.D.)--University of Florida, 2012.
Local: Adviser: Cook, Ronald A.

Record Information

Source Institution: UFRGP
Rights Management: Applicable rights reserved.
Classification: lcc - LD1780 2012
System ID: UFE0044501:00001

Permanent Link: http://ufdc.ufl.edu/UFE0044501/00001

Material Information

Title: Sustained Load Performance of Adhesive Anchor Systems in Concrete
Physical Description: 1 online resource (570 p.)
Language: english
Creator: Davis, Todd M
Publisher: University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: 2012

Subjects

Subjects / Keywords: adhesive -- anchor -- concrete -- creep -- sustained
Civil and Coastal Engineering -- Dissertations, Academic -- UF
Genre: Civil Engineering thesis, Ph.D.
bibliography   ( marcgt )
theses   ( marcgt )
government publication (state, provincial, terriorial, dependent)   ( marcgt )
born-digital   ( sobekcm )
Electronic Thesis or Dissertation

Notes

Abstract: Stemming from a tragic failure of an adhesive anchor system, this research project investigated the sustained load performance of adhesive anchors in concrete under different installation and in-service conditions. The literature review investigated the current state of art of adhesive anchors.  Extensive discussion was devoted to the behavior of adhesive anchors in concrete as well as the many factors that can affect their short-term and sustained load strength.  Existing standards and specifications for the testing, design, construction, and inspection of adhesive anchors were covered. Based on the results of the literature review and the experience of the research group, a triage was conducted on many parameters identified as possibly affecting the sustained load performance of adhesive anchors and the highest priority parameters were investigated in this project.  A stress versus time-to-failure approach was used to evaluate sensitivity of three ICC-ES AC 308 approved adhesive anchor systems.  Of the various parameters investigated, only elevated in-service temperature and manufacturer’s cure time was shown to exhibit adverse effects on sustained loads more than that predicted by short-term tests of fully cured adhesive over a reasonable structure lifetime of 75 years. In a related study, various tests were conducted on the adhesive alone (time-temperature superposition, time-stress superposition, and dogbone tensile tests).  The results of that study were used to investigate the existence of a correlation with long-term anchor pullout testing in concrete.  No consistent correlations were detected for the adhesives in the study. Tests were also conducted on the effect of early-age concrete on adhesive anchor bond strength.  On the basis of confined test bond-strength alone, adhesive A (vinyl ester) did not show any significant increase after 14 days (102% of 28 day strength at 14 days), and adhesive B and C (epoxies) did not show any significant increase after 7 days (104% and 93% of 28 days strength at 7 days respectively). The results of this research were used to draft recommended standards and specifications for AASHTO pertaining to testing, design, construction, and inspection of adhesive anchors in concrete for transportation structures.  These draft standards were not included in this dissertation.
General Note: In the series University of Florida Digital Collections.
General Note: Includes vita.
Bibliography: Includes bibliographical references.
Source of Description: Description based on online resource; title from PDF title page.
Source of Description: This bibliographic record is available under the Creative Commons CC0 public domain dedication. The University of Florida Libraries, as creator of this bibliographic record, has waived all rights to it worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law.
Statement of Responsibility: by Todd M Davis.
Thesis: Thesis (Ph.D.)--University of Florida, 2012.
Local: Adviser: Cook, Ronald A.

Record Information

Source Institution: UFRGP
Rights Management: Applicable rights reserved.
Classification: lcc - LD1780 2012
System ID: UFE0044501:00001


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1 SUSTAINED LOAD PERFORMANCE OF ADHESIVE ANCHOR SYSTEMS IN CONCRETE By TODD MARSHALL DAVIS A DISSERTATION PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY UNIVERSITY OF FLORIDA 2012

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2 2012 Todd Marshall Davis

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3 To Milena and Angel Del Valle

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4 ACKNOWLEDGMENTS This project was conducted with the help from many individuals, companies, and organizations to whom I am grateful for their involvement. First and foremost, I would like to thank my advisor Dr. Ronald A. Cook for his excellent guidance, trust in my abilities and genuine friendship these past five years. Also I wish to thank my committee: Dr. Elliot Douglas, Dr. Kurt Gurley, Dr. Trey Hamilton, and Dr. Mang Tia T heir different backgrounds and strengths have made me a better engineer, and each one impacted t he quality of this dissertation. The major portion of this research was funded by t he National Cooperative Highway Research Program (NCHRP) under project 0437 and managed by Dr. Ed Harrigan of the Transportation Research Board (TRB) of The National Academies. This research built upon previous work by the author also funded by NCHRP und er project 2007/Task 255 and managed by Dr. Ed Harrigan and can be found in NCHRP Report 639. Additional funding for the author was provided by the University of Florida Alumni Fellowship and the Deutscher Akademischer Austausch Dienst (DAAD) Ph. D Research Grant Several UF personnel ( Jim Austin, Chuck Broward, Dr. Chris Ferraro, and Nard Martin), UF graduate students ( Patrick Bekoe, Joshua Burkard, Sadie Dalton, Kunal Malpani, Kenton McBride, Sangam Nitesh, Siddarth Pandey, Jessica Rigdon, and Yongyang Tang), and UF undergraduate students ( Victor Konn, Scott Maul, and Melissa Smith ) assisted the author in the experimental testing for the anchor pullout tests at the University of Florida. Ph.D. student Yu min Su of the Advanced Materials Characterization Laboratory (AMCL) at the University of Florida assisted in the operation of the X ray Computed Tomography (CT) system in the failure investigation of

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5 several adhesive anchor specimens. Dr. Gary Consolazio provided guidance in the viscoelastic adhesive anchor finite element analysis model. The majority of the concrete specimens for the anchor pullout tests at the University of Florida were batched and cast at the Florida Department of Transportation (FDOT) State Materials Office. FDOT personnel assisted i n the mix design and production of the test specimens, namely: Patrick Carlton, Dale DeFord, Richard DeLorenzo, Cleveland English, Joe Fitzgerald, Charles Ishee, and Jordan Nelson. Two local fabricators, Boone Welding and Rogers Welding, assisted in the fa brication of the testing equipment. The FDOT State Materials Office provided the compression springs for the sustained load testing frames. The local concrete ready mix supplier, Florida Rock, provided concrete for a few test specimens and donated the fl y ash and blast furnace slag Hollanders Hydraulics Inc. fabricated a hydraulic jack chair for the sustained load testing frame. The three adhesive anchor manufacturers (names withheld) were very generous in donating adhesive product and equipment for t he experimental program. Anchor rods were provided by Glaser and Associates of Martinez, CA and American Supply Company of Jackson, MS. The experimental work conducted at the Institt fr Werkstoffe im Bauwesen (IWB) laboratory at the University of Stuttg art in Germany was conducted by Ph.D. student Ronald Blochwitz and supervised by Dr. Jan Hofmann and Dr. Rolf Eligehausen. The adhesive alone testing was conducted by UF graduate student Laura Diers and Ph.D. student Changhua Liu under the supervision of D r. Elliot Douglas.

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6 The research on the effect of early age concrete on the short term bond strength was conducted by the author at the IWB laboratories at the University of Stuttgart. The research was partially funded by IWB and a Deutscher Akademischer A ustausch Dienst (DAAD) Ph D R esearch Grant. Several IWB staff members were instrumental in orienting the author to the laboratory and Germany namely: Walter Berger, Ronald Blochwitz, Silvia Choynacki, Rolf Eligehausen, Christian Fischer, Werner Fuchs, Paul Geiger, Philipp Grosser, Jan Hofmann, Carolin Kurz, Eugen Lindenmeier, Dnes Sndor, Peter Scherf, Bernd Schlottke, and Monika Werner UF Ph D student Kenton McBride assi sted the author in the development of a modified initial surfa ce absorption test (ISAT) on the sides of the anchor holes. Most of all, I would like to thank my lovely bride and best friend, Shana. She has been a constant supporter, encourager, and sounding board during these five years in graduate school.

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7 TABLE OF CONTENTS page ACKNOWLEDGMENTS .................................................................................................. 4 LIST OF TABLES .......................................................................................................... 16 LIST OF FIGURE S ........................................................................................................ 20 LIST OF ABBREVIATIONS ........................................................................................... 38 ABSTRACT ................................................................................................................... 40 CHAPTER 1 BACKGROUND ...................................................................................................... 42 Introduction ............................................................................................................. 42 Background on Be havior/Design of Anchors .......................................................... 42 Behavioral Model .............................................................................................. 42 Short term Sensitivity ....................................................................................... 45 Sustai ned Load Influence ................................................................................. 46 Summary ................................................................................................................ 47 2 LITERATURE REVIEW .......................................................................................... 52 Parameters Influencing Bond Strength ................................................................... 52 In Service Factors ............................................................................................ 53 Factors Related to the Adhesive ...................................................................... 55 Installation Factors ........................................................................................... 57 Synergistic effects ............................................................................................ 62 Test Met hods and Material Specifications Related to Adhesive Anchor Systems .. 62 ASTM E488 Standard Test Methods for Strength of Anchors in Concrete and Masonry Elements ................................................................................. 62 ASTM E1512 Standard Test Methods for Testing Bond Performance of Bonded Anchors ............................................................................................ 64 ICCES AC58 Acceptance Criteria for Adhesive Anchors in Concrete and Masonry Elements ........................................................................................ 68 Service condition tests ............................................................................... 69 Suit ability requirement tests ....................................................................... 69 ICCES AC308 Acceptance Criteria for Post Installed Adhesive Anchors in Concrete Elements ........................................................................................ 73 ACI 355.4 11 Qualification of Post Installed Adhesive Anchors in Concrete .... 73 Assessment approach ............................................................................... 75 Identifi cation tests ...................................................................................... 76 Reference tests .......................................................................................... 76 Reliability tests ........................................................................................... 77

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8 Service condition tests ............................................................................... 83 Additional supplemental tests .................................................................... 89 Additional assessm ent tests ....................................................................... 90 Resulting design values ............................................................................. 91 Anchor categories ...................................................................................... 92 AASHTO Standard Specifications for Transportation Materials and Methods of Sampling and Testing ............................................................................... 92 CALTRANS CTM681 Method for Testing Creep Performance of Concrete Anchorage Systems ...................................................................................... 93 CALTRANS Standard Specifications ................................................................ 93 TxDOT DMS 6100 Epoxies and Adhesives ................................................... 94 TxDOT Tex 614J Testing Epoxy Materials ...................................................... 94 NYSDOT Standard Specifications .................................................................... 95 NYSDOT Engineering Instruction EI 08012 .................................................... 96 FDOT FM 5 568 Florida Method of Test for Anchor Systems for Adhesive Bonded Anchors and Dowels. ....................................................................... 97 FDOT Standard Specifications for Road and Bridge Construction ................... 98 IDOT Laboratory Test Procedure for Chemical Adhesives ............................... 99 IDOT Standard Specifications for Road and Bridge Construction .................. 101 WSDOT Standard Specifications ................................................................... 101 MDOT Material Source Guide ........................................................................ 101 VDOT Road and Bridge Specifications .......................................................... 101 EOTA ETAG 001 Part 5 Bonded Anchors ................................................... 102 fib Design of Anchorages in Concrete ............................................................ 102 Short Term Incremental Loading Test for Adhesive Anchors ......................... 102 Stress Versus Time to Failure Test ................................................................ 103 Adhesive Alone Tests ..................................................................................... 104 Time temperature superposition and master curves ................................ 104 Time stress superposition ........................................................................ 105 Dynamic Mechanical Thermal Analysis (DMTA) tests ............................. 106 Creep compliance curves ........................................................................ 107 California Department of Transportation (CALTRANS) TM 438 ............... 107 Tensile creep tests ................................................................................... 107 Design Guidelines and Specifications Related to Adhesive Anchor Systems ....... 108 ICCES AC308 Acceptance Criteria for Post Installed Adhesive Anchors in Concrete Elements ...................................................................................... 109 ACI 318 11 Building Code Requirements for Structural Concrete .................. 109 Te nsion .................................................................................................... 109 Shear ....................................................................................................... 113 Tension and shear interaction .................................................................. 115 AASHTO LRFD Bridge Design Specifications ................................................ 116 AASHTO Standard Specifications for Structural Supports for Highway Signs, Luminaires and Traffic Signals ......................................................... 116 NCHRP Report 469 Fatigue Resistant Design of Cantilevered Signal, Sign, and Light Supports ...................................................................................... 117 NYSDOT Bridge Design Manual .................................................................... 118

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9 FDOT Structures Manual ................................................................................ 118 Tens ion .................................................................................................... 118 Shear ....................................................................................................... 119 Tension and shear interaction .................................................................. 120 IDOT Bridge Manual ....................................................................................... 120 PENNDOT Design Manual Part 4 Structures ............................................... 121 WSDOT Bridge Design Manual ...................................................................... 121 MDOT Bridge Design Manual ......................................................................... 122 MDOT Moratorium on the Use of Adhesive Anchors in Sustained TensileLoadOnly Overhead Applications ............................................................... 122 VDOT IIM S&B40.2 Sound Barrier Wall Attachments ................................... 122 VDOT IIM S&B76.2 Adhesive Anchors for Structural Applications ............... 123 EOTA ETAG 001 Annex C Design Methods for Anchorages ...................... 123 fib Design of Anchorages in Concrete ............................................................ 123 Tension .................................................................................................... 123 Shear ....................................................................................................... 125 Tension and shear interaction .................................................................. 126 Quality Assurance Guidelines and Construction Specifications Related to Adhesive Anchor Systems ................................................................................. 126 ICCES AC308 Acceptance Criteria for Post Installed Adhesive Anchors in Concrete Elements ...................................................................................... 126 ACI 355.4 11 Qualification of Post Installed Adhesive Anchors in Concrete .. 126 AASHTO LRFD Bridge Construction Specifications ....................................... 128 AASHTO Standard Specifications for Structural Supports for Highway S igns, Luminaires and Traffic Signals ......................................................... 128 NCHRP Report 469 Fatigue Resistant Design of Cantilevered Signal, Sign, and Light Supports ...................................................................................... 128 CALTRANS Standard Specifications .............................................................. 129 TxDOT Standard Specifications for Construction and Maintenance of Highways, Streets, and Bridges .................................................................. 129 NYSDOT Standard Specifications .................................................................. 129 FDOT Standard Specifications for Road and Bridge Construction ................. 130 IDOT Standard Specifications for Road and Bridge Construction .................. 131 WSDOT Construction Manual ........................................................................ 132 MDOT Standard Specifications for C onstruction ............................................ 132 EOTA ETAG 001 ............................................................................................ 132 Manufacturers Printed Installation Instructions .............................................. 133 Manufacturer X ........................................................................................ 133 Manufacturer Y ........................................................................................ 134 Manufacturer Z ......................................................................................... 135 Summary .............................................................................................................. 136 3 TESTING PROGRAM ........................................................................................... 153 Parameters Identified for Testing .......................................................................... 153 High Priority Parameters ................................................................................ 154 Medium Priority Parameters ........................................................................... 157

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10 Low Priority Parameters ................................................................................. 159 Anchor Pullout Testing Program ........................................................................... 162 Adhesive Alone Testing Program ......................................................................... 163 Early Age Concrete Testing Program ................................................................... 164 Summary .............................................................................................................. 164 4 METHODS AND MATERIALS .............................................................................. 168 Anchor Pullout Tests University Of Florida ........................................................ 168 Overview ........................................................................................................ 168 Concrete .................................................................................................. 168 Adhesive .................................................................................................. 168 Anchor ..................................................................................................... 169 Test procedure ......................................................................................... 169 Test Apparatus ............................................................................................... 170 Standard short term (reference) test apparatus ....................................... 170 Test series 16 (unconfined) short term test apparatus ............................. 171 Standard sustained load (creep) test apparatus ...................................... 171 Test series 16 (unconfined) sustained load test apparatus ...................... 173 Specimen Preparation .................................................................................... 173 Concrete test member ............................................................................. 173 Adhesive .................................................................................................. 176 Anchor rods .............................................................................................. 176 Instrumentation ............................................................................................... 176 Measurement ........................................................................................... 176 Instrument calibration ............................................................................... 178 Environmental Control .................................................................................... 179 Standard temperature .............................................................................. 179 Elevated temperature ............................................................................... 179 Data Management and Acquisition ................................................................. 1 80 Data sampling program ............................................................................ 180 Short term (reference) test program ......................................................... 180 Long term (creep) test program ............................................................... 181 Test specimen conditioning program ....................................................... 181 Installation Procedure ..................................................................................... 182 Standard baseline installation procedure ................................................. 182 Test series 7 (moisture during installation) installation procedure ............ 183 Test series 9 (reduced hole cleaning) installation procedure ................... 184 Test series 13 (type of drilling) installation procedure .............................. 184 Specimen Conditioning .................................................................................. 185 Testing Procedure .......................................................................................... 185 Standard short term (reference) test procedure ....................................... 186 Test series 16 (unconfined) test procedure .............................................. 187 Standard sustained load (creep) test procedure ...................................... 187 Test series 16 (unconfined) test procedure .............................................. 189 Post test procedure .................................................................................. 189 Anchor Pullout Tests University of Stuttgart ....................................................... 189

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11 Adhesive Alone Tests University of Florida ........................................................ 190 Early Age Concrete Evaluation University of Stuttgart ....................................... 190 Overview ........................................................................................................ 190 Test Apparatus ............................................................................................... 190 Short term ( reference) anchor pullout test apparatus .............................. 190 Initial surface absorption test apparatus .................................................. 191 Rebound hammer .................................................................................... 191 Indention hammer .................................................................................... 192 Specimen Preparation .................................................................................... 192 Concrete test member ............................................................................. 192 Adhesive .................................................................................................. 194 Anchor rods .............................................................................................. 194 Instrumentation ............................................................................................... 194 Measurement ........................................................................................... 194 Instrument calibration ............................................................................... 196 Data Management and Acquisition ................................................................. 196 Installation Procedure ..................................................................................... 196 Testing Procedure .......................................................................................... 197 Short term (reference) test procedure ...................................................... 197 Initial surface absorption test procedure .................................................. 197 Rebound hammer test procedure ............................................................ 202 Indention hammer test procedure ............................................................ 202 Roughness ............................................................................................... 203 Short Term Anchor Pullout Data Reduction .......................................................... 203 Displacement adjustments ............................................................................. 203 Determining short term load strength ............................................................. 204 Short term bond stress ................................................................................... 206 Sustained Load Anchor Pullout Data Reduction ................................................... 207 Assessment of a Parameters Impact on Sustained Load Performance ............... 209 Recommendations ................................................................................................ 210 Summary .............................................................................................................. 210 5 ANCHOR PULLOUT TES T RESULTS ................................................................. 241 Short Term Anchor Pullout Load Testing .............................................................. 241 Short term Load Test Results ......................................................................... 241 Statistical analysis .................................................................................... 241 Bond s tress analysis ................................................................................ 243 Discussion on unconfined results ............................................................. 243 Selection of Adhesive for Sustained Load Investigation ................................. 246 Sustained Load Anchor Pullout Testing ................................................................ 248 Modification to Testing Program ..................................................................... 248 Sustained Load Displacement versus Time Test Results .............................. 248 Core Sample Analysis ........................................................................................... 248 X ray Investigation of Failure Surface ................................................................... 250 Short term Load Test Specimen (Prefailure) ................................................. 251 Sustained Load Test Specimen (Prefailure) .................................................. 251

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12 Short term Load Test Specimen (Post failure) ............................................... 252 Findings from X ray Study .............................................................................. 252 Summary .............................................................................................................. 253 6 STRESS VERSUS TIME TO FAILURE AND SUSTAINED LOAD INFLUENCE RESULTS ............................................................................................................. 268 Model Equation for Stress versus Timeto Failure Relationship ........................... 268 Exclusion of Short term Tests in Stress versus Timeto Failure Relationship ....... 268 Combined SvTTF Baseline Curves ....................................................................... 270 Rejection of Failures During Loading .................................................................... 270 Tests Terminated Prior to Failure ......................................................................... 271 Tests Still Runnin g at Time of Publishing .............................................................. 271 Sustained Load Influence ..................................................................................... 271 Influence Ratio with Actual Alpha Reduction Factors ..................................... 271 Influence Ratio with Alpha Reduction Factors Limited to a Maximum Value of 1 .............................................................................................................. 272 Influence Ratio of Nomin al Strength ............................................................... 273 Stress Versus Time To Failure and Sustained Load Influence Statistical Analysis ............................................................................................................. 273 Method 1: Comparison of Slopes ................................................................... 274 Method 2: Comparison of Experimental Values to Alphabaseline ................. 275 Method 3: Comparison of Experimental Values Beyond 100 Hours to Alphabaseline ....................................................................................................... 276 Method 4: Monte Carlo Simulation to Evaluate Sustained Load Influence ..... 276 Discussion on Sustained Load Influence .............................................................. 278 Parameters with Adverse Sustained Load Influence ...................................... 279 Parameters without Adverse Sustained Load Influence ................................. 281 Summary .............................................................................................................. 286 7 VISCOELASTIC STUDY OF ADHESIVE ANCHORS ........................................... 298 Incremental Load Rate Investigation .................................................................... 298 Finite Element Investigation .................................................................................. 299 Material Models .............................................................................................. 299 Finite Element Analysis .................................................................................. 300 P EPA Model .................................................................................................. 301 V EPA Model .................................................................................................. 301 Summary .............................................................................................................. 302 8 CORRELATION WITH ADHESIVE ALONE TESTS ............................................. 310 Mechanics of Dogbones and Adhesive Anchor Systems ...................................... 310 Strain in Dogbone Specimens ........................................................................ 310 Strain in Adhesive Anchor System ................................................................. 310 Comparison of Strains .................................................................................... 312 Sustained Load Test Results ................................................................................ 312

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13 Stress versus Time to Failure Results for Anchor Pullout and Dogbone Tests ..... 313 Summary .............................................................................................................. 313 9 EARLY AGE CONCRETE TEST RESULTS ......................................................... 320 Short term Test Results ........................................................................................ 320 Discussion of Anomalies ....................................................................................... 320 Temperature and Humidity ................................................................................... 321 Initial Surface Absorption ...................................................................................... 323 Hardness .............................................................................................................. 324 Summary .............................................................................................................. 324 10 CONCLUSIONS AND RECOMMENDATIONS ..................................................... 331 Summary .............................................................................................................. 331 Anchor Pullout Testing ................................................................................... 331 Stress versus Time to Failure and Sustained Load Influence ......................... 332 Viscoelastic Study of Adhesive Anchors ......................................................... 333 Correlation between Adhesive Anchor Tests and Adhesive Alone Tests ....... 333 Early Age Concrete Tests ............................................................................... 333 Observations and Conclusions ............................................................................. 333 Anchor Pullout Testing ................................................................................... 333 Stre ss versus Time to Failure and Sustained Load Influence ........................ 334 Stress versus time to failure .................................................................... 334 Sustained load influence .......................................................................... 334 Viscoelastic Study of Adhesive Anchors ......................................................... 334 Incremental load tests .............................................................................. 334 Finite element analysis ............................................................................ 335 Correlation between Adhesive Anchor Tests and Adhesive Alone Tests ....... 335 Early Age Concrete Investigation ................................................................... 336 Recommendations ................................................................................................ 337 Anchor Pullout Testing ................................................................................... 337 Stress versus Time to Failure ......................................................................... 337 Sustained Load Influence ............................................................................... 337 Viscoelastic Study of Adhesive Anchors ......................................................... 338 Early age Concrete Investigation ................................................................... 338 APPENDIX A CONCRETE MIX DESIGNS ................................................................................. 339 B ANCHOR PULLOUT TESTS UNIVERSITY OF STUTTGART ........................... 371 Overview ............................................................................................................... 371 Concrete ......................................................................................................... 371 Adhesive ......................................................................................................... 371 Anchor ............................................................................................................ 372

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14 Test Procedure ............................................................................................... 372 Test Apparatus ..................................................................................................... 372 Standard Short term (Reference) Test Apparatus .......................................... 372 Standard Sustained Load (Creep) Test Apparatus ......................................... 374 Specimen Preparation .......................................................................................... 375 Concrete Test Member ................................................................................... 376 Adhesive ......................................................................................................... 376 Anchor Rods ................................................................................................... 377 Instrumentation ..................................................................................................... 377 Measurement ................................................................................................. 377 Instrument Calibration .................................................................................... 379 Environmental Control .......................................................................................... 380 Standard Temperature ................................................................................... 380 Elevated Temperature .................................................................................... 381 Data M anagement and Acquisition ....................................................................... 381 Data Acquisition Software for Short term (Reference) Tests .......................... 382 Data Acquisition Software for Sustained Load (creep) Tests ......................... 382 Installation Procedure ........................................................................................... 382 Stan dard Baseline Installation Procedure ....................................................... 382 Exceptions to the Standard Baseline Installation Procedure .......................... 384 Specimen Conditioning ......................................................................................... 384 Testing Procedure ................................................................................................ 384 Standard Short term (Reference) Test Procedure .......................................... 384 Standard Sustained Load (Creep) Test Procedure ........................................ 385 Exceptions to the Standard Baseline Testing Procedure ............................... 387 Post Test Procedure ....................................................................................... 387 C ADHESIVE ALONE TESTS UNIVERSITY OF FLORIDA ................................... 405 Overview ............................................................................................................... 405 Test Apparatus ..................................................................................................... 405 Dogbone Short term (Reference) Testing Apparatus ..................................... 406 Dogbone Sustained Load (Creep) Testing Apparatus .................................... 406 DSR Machine ................................................................................................. 407 Specimen Fabrication ........................................................................................... 407 Adhesive ......................................................................................................... 407 Dogbone Sample ............................................................................................ 407 Specimens for DMTA and Creep Testing ....................................................... 408 Instrumentation ..................................................................................................... 409 Measurement ................................................................................................. 409 Instrument Calibration .................................................................................... 410 Environmental Control .......................................................................................... 411 Standard Temperature ................................................................................... 411 Elevated Temperature .................................................................................... 411 Data Management and Acquisition ....................................................................... 411 Data Sampling Program ................................................................................. 412 Long Term (Creep) Test Program .................................................................. 412

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15 Specimen Preparation Procedure ......................................................................... 413 Dogbone Specimen Preparation .................................................................... 413 DMTA and Creep Specimen Preparation ....................................................... 413 Specimen Conditioning .................................................................................. 414 Dogbone Short term (Reference) Testing ...................................................... 414 Dogbone Sustained Load (Creep) Testing ..................................................... 414 DMTA and Creep Testing ............................................................................... 414 Testing Procedure ................................................................................................ 414 Dogbone Short term (Reference) Test Procedure .......................................... 415 Dogbone Sustained Load (Creep) Test Procedure ........................................ 415 DMTA and Creep Test Procedure .................................................................. 415 D SHORT TERM TEST RESULTS .......................................................................... 424 E ADHESIVE ANCHOR POST TEST SPLIT CORE INVESTIGATION ................... 473 F TIME TO RUPTURE VERSUS TIME TO TERTIARY CREEP COMPARISON .... 484 G SUSTAINED LOAD CREEP TEST RESULTS ...................................................... 487 H STRESS VERSUS TIME TO FAILURE PLOTS ................................................... 498 I ADHESIVE ALONE TEST RESULTS ................................................................... 522 Short term Results ................................................................................................ 522 DMTA Results ....................................................................................................... 522 Sustained Load Strain versus Time Results ......................................................... 523 Sustained Load Compliance versus Time Results ................................................ 523 Discussion and Recommendations ....................................................................... 528 J EARLY AGE CONCRETE INVESTIGATION SHORT TERM TEST RESULTS ... 544 LIST OF REFERENCES ............................................................................................. 561 BIOGRAPHICAL SKETCH .......................................................................................... 570

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16 LIST OF TABLES Table page 2 1 ACI 355.4 11 (2011) Table 8.1 Minimum test temperatures ........................... 137 2 2 CALTRANS (2001) CTM681 sustained load values ......................................... 137 2 3 Performance requirements for type III adhesives tested with TxDOT (2007b) Tex 614J ......................................................................................................... 137 2 4 NYSDOT (2008b) chemical resistance requirements ....................................... 138 2 5 NYSDOT (2008b) anchor tests minimum pullout loads .................................... 138 2 6 FDOT (2000) FM 5 568 minimum performance requirements for adhesive systems ............................................................................................................ 138 2 7 ACI 318 11 (2011) characteristic bond stress to use in absence of test results 138 2 8 CALTRANS (2006b) installation torque values ................................................. 139 3 1 Prioritization of identified parameters ............................................................... 165 3 2 Test ma trix for anchor pullout testing ................................................................ 166 3 3 Proposed Test Matrix for Tensile Creep Testing .............................................. 167 4 1 Test descriptions .............................................................................................. 211 4 2 Concrete pour details ....................................................................................... 211 4 3 Concrete series average compressive strength ................................................ 211 4 4 Full hole cleaning procedures per MPII ............................................................ 212 4 5 Reduced hole cleaning procedures .................................................................. 212 4 6 Early age concrete compression strength results ............................................. 212 4 7 Early age concrete split tensile strength results ............................................... 212 5 1 Statistical analysis for short term tests on adhesive A at University of Florida 254 5 2 Statistical analysis for short term tests on adhesive B at University of Florida 254 5 3 Statistical analysis for short te rm tests on adhesive C at University of Florida 255

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17 5 4 Statistical analysis for short term tests on adhesive A at Universi ty of Stuttgart ............................................................................................................ 255 5 5 Statistical analysis for short term tests on adhesive B at University of Stuttgart ............................................................................................................ 255 5 6 Statistical analysis for short term tests on adhesive C at University of Stuttgart ............................................................................................................ 256 5 7 Comparison of late baseline tests to initial baseline tests ................................. 256 5 8 Statistical analysis for late short term tests on adhesive A at University of Stuttgart ............................................................................................................ 256 5 9 Statistical analysis for late short term tests on adhesive B at University of Stuttgart ............................................................................................................ 257 5 10 Bond stress analysis ......................................................................................... 257 5 11 Test series 16 (unconfined setup) short term verification tests results with adhesive C in higher strength concrete at 110 F .............................................. 257 5 12 Test series 16 (unconfined setup) short term verification tests results with adhesive C in higher strength concrete at 80 F ................................................ 257 5 13 Summary of alpha reduction factors ................................................................. 258 5 14 Glass transition temperatures ........................................................................... 258 5 15 Alkalinity sensitivity reduction factor ................................................................. 258 5 16 Degree of cross linking ..................................................................................... 259 5 17 Lowest manufacturer specified installation temperature ................................... 259 6 1 Expected failure stress level at five minute load duration for baseline tests with short term tests excluded in the SvTTF projection .................................... 288 6 2 Peak displacement data for short term (ST) an d long term sustained load (LT) tests for UF baselines ............................................................................... 288 6 3 Displacement data at loss of adhesion per ACI 355.411 for short term (ST) tests and peak displacement data for long term sustained load (LT) tests for UF baselines ..................................................................................................... 288 6 4 Summary of Influence Ratios and confidence level from Monte Carlo simulation ......................................................................................................... 289 7 1 Shear modulus and bulk modulus values for viscoelastic model ...................... 304

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18 7 2 Time step schedule for finiteelement analysis ................................................. 304 9 1 Temperature readings for the early age concrete evaluation ........................... 327 9 2 Relative humidity readings for the early age concrete evaluation ..................... 327 9 3 ISAT 10 minute sample data and relative humidity for sides of hole and formed surface .................................................................................................. 327 9 4 Rebound and indention hammer results ........................................................... 327 A 1 Concrete mixes used for each test ................................................................... 339 A 2 Concrete mix design for mix US:A .................................................................... 370 A 3 Concrete mix design for mix US:B .................................................................... 370 B 1 Test descriptions .............................................................................................. 3 89 B 2 Concrete pour details ....................................................................................... 389 B 3 Concrete series US A average compressive strength ...................................... 389 B 4 Concrete series US B average compressive strength ...................................... 389 C 1 Test descriptions .............................................................................................. 417 D 1 University of Florida short term anchor pullout test results failure loads ........ 425 D 2 University of Florida short term anchor pullout test results failure stresses ... 426 D 3 University of Florida short term anchor pullout test results failure displacements ................................................................................................... 427 D 4 University of Stuttgart short term anchor pullout test results failure loads ..... 428 D 5 University of Stuttgart short term anchor pullout test results failure stresses 429 D 6 University of Stuttgart short term anchor pullout test results failure displacements ................................................................................................... 430 D 7 University of Florida and University of Stuttgart late baseline short term test results failure loads ........................................................................................ 430 D 8 Universit y of Florida and University of Stuttgart late baseline short term test results failure stresses ................................................................................... 430 D 9 University of Flo rida and University of Stuttgart late baseline short term test results failure displacements ......................................................................... 431

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19 D 10 University of Flor ida short term dogbone test results failure stresses ........... 431 D 11 University of Florida short term dogbone test results failure strains .............. 431 D 12 Results of modified Thompson tau technique ................................................... 431 F 1 University of Florida adhes ive A anchor pullout tertiary creep and rupture failure times ...................................................................................................... 484 F 2 University of Florida adhesive B anchor pullout terti ary creep and rupture failure times ...................................................................................................... 484 F 3 University of Florida adhesive C anchor pullout tertiary creep and rupture failure times ...................................................................................................... 485 F 4 University of Stuttgart adhesive A anchor pullout tertiar y creep and rupture failure times ...................................................................................................... 485 F 5 University of Stuttgart adhesive B anchor pullout tertiary creep and rupture failure times ...................................................................................................... 486 F 6 University of Stuttgart adhesive C anchor pullout tertiary creep and rupture failure times ...................................................................................................... 486 I 1 Summary of alpha reduction factors ................................................................. 530 J1 Early age concrete short term anchor pullout test results failure loads ......... 544 J2 Early age concrete short term anchor pullout test results failure stresses .... 545 J3 Early age concrete short term anchor pullout test results failure displacements ................................................................................................... 545

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20 LIST OF FIGURES Figure page 1 1 Potential embedment failure modes of bonded anchors ..................................... 48 1 2 Mechanism of load transfer of a bonded anchor ................................................. 48 1 3 Hyperbolic tangent stress distribution ................................................................. 49 1 4 Stress distribution along length of adhesive anchor for hef/do = 4.00 .................. 49 1 5 Stress distribution along length of adhesive anchor for hef/do = 5.33 .................. 49 1 6 St ress distribution along length of adhesive anchor for hef/do = 6.67 .................. 50 1 7 Stress distribution along length of adhesive anchor for hef/do = 8.00 .................. 50 1 8 Uniform bond stress model for adhesive anch o rs ............................................... 50 1 9 Calculation of short term ..................................................... 51 2 1 Typical capsule anchor system ......................................................................... 140 2 2 Typical injection anchor system ........................................................................ 140 2 3 Various relationships of bond strength as a function of concrete strength ........ 140 2 4 Typical crack location of bonded anchor ......................................................... 141 2 5 Sample bond strength versus temperature curve for three hypothetical adhesives ......................................................................................................... 141 2 6 Extrapolation of sus tained load displacements per ASTM E1512 .................... 142 2 7 Basic pass/fail criteria per ICC ES AC58 .......................................................... 142 2 8 Evaluation of load at Nadh ................................................................................. 143 2 9 Evaluation of load at Nadh ................................................................................. 143 2 10 Evaluation of load at Nadh ................................................................................. 144 2 11 Evaluation of load at Nadh ................................................................................. 144 2 12 Procedure for verifying the effectiveness of overhead adhesive injection ........ 145 2 13 Punch test apparatus ........................................................................................ 145

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21 2 14 Load versus displacement and time versus displacement graph for a sample anchor with incremental loading ....................................................................... 146 2 15 Sample stress versus timeto failure graph ...................................................... 146 2 16 Sample master curve using timetemperature superposition ............................ 147 2 17 Individual compliance curves used in time stress superposition ....................... 147 2 18 Sample master curve using time stress superposition ..................................... 148 2 19 E' and E" master curves for an epoxy ............................................................... 148 2 20 tan delta master curve for an epoxy ................................................................. 149 2 21 Creep compliance curve for two epoxies .......................................................... 149 2 22 ASTM D63 8 Type I and Type II specimens ...................................................... 150 2 23 A CI 318 11 tension failure modes .................................................................... 151 2 24 ACI 318 11 shear failure modes ....................................................................... 152 4 1 Short term (reference) confined test apparatus ................................................ 213 4 2 Test series 16 short term (reference) unconfined test apparatus ..................... 213 4 3 Sustained load (creep) confined test apparatus ............................................... 214 4 4 Test frame with hydraulic jack chair shown in red ............................................ 214 4 5 Test series 16 sustained load (creep) unconfined test apparatus ..................... 215 4 6 Concrete test specimens being cast ................................................................. 215 4 7 Ovens ............................................................................................................... 216 4 8 Mixer ................................................................................................................. 216 4 9 Compression machine ...................................................................................... 217 4 10 Cylinder grinding machine ................................................................................ 217 4 11 Walk in stability chamber .................................................................................. 218 4 12 Left side of testing chamber ............................................................................. 218 4 13 Right side of testing chamber ........................................................................... 219 4 14 Layout of anchor pull out test frames in the stability chamber .......................... 220

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22 4 15 Data sampling LabVIEW program .................................................................... 221 4 16 Short term test LabVIEW program (main screen) ............................................. 221 4 17 Short term test LabVIEW program (chart page) ............................................... 222 4 18 Sustained load test LabVIEW program (main screen) ...................................... 222 4 19 Sustained load test LabVIEW program (displacement plot) ............................. 223 4 20 Sustained load test LabVIEW program (percent load plot) ............................... 223 4 21 Drilling rig and hammer drill .............................................................................. 224 4 22 Vacuum adaptor ............................................................................................... 224 4 23 Embedment depth chair ................................................................................... 225 4 24 Water dam for test series 7 installation ............................................................. 225 4 25 Core drill for test series 13 ................................................................................ 226 4 26 Water collector .................................................................................................. 226 4 27 Extraction tool ................................................................................................... 227 4 28 Air nozzle .......................................................................................................... 227 4 29 Short t erm testing apparatus ............................................................................ 228 4 30 LVDT rig ........................................................................................................... 228 4 31 ISAT equipment ................................................................................................ 229 4 32 Rebound hammer ............................................................................................. 229 4 33 Ind ention hammer ............................................................................................. 230 4 34 MPA universal testing machine ........................................................................ 230 4 35 MPA cylinder grinding machine ........................................................................ 231 4 36 Anchor showing 45 cone to fit into centering guide ......................................... 231 4 37 Sensiron sensor assembly ............................................................................... 232 4 38 PVC pipes and Sensiron sensors placed in forms prior to casti ng ................... 232 4 39 Screenshot of NI DIAdem 10.2 data acquisition program ................................. 233

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23 4 40 Chipped area around top of hole ...................................................................... 233 4 41 Jig to measure the diameter of the chipped area in four directions .................. 234 4 42 A2 sub areas ..................................................................................................... 234 4 43 Core with drilled hole split for roughness evaluation ......................................... 235 4 44 Removing the effect of slack in the loaddisplacement graph ........................... 235 4 45 Typic al strengthcontrolled failure ..................................................................... 236 4 46 Typica l stiffnesscontrolled failure ..................................................................... 236 4 47 Typical d isplacement controlled failure ............................................................. 237 4 48 Example of calculating short term load strength from various methods ........... 237 4 49 Example of the change in slope method ........................................................... 238 4 50 Typical TS16 sustained load bond with shallow cone failure ............................ 238 4 51 Test series 16 (unconfined setup) sustained load tests percent MSL versus time plot ............................................................................................................ 239 4 52 Test series 16 (unconfined setup) sustained load tests displacement versus time plot ............................................................................................................ 239 4 53 Stress versus time to failure comparison of experimental, baseline and alphabaseline trends ....................................................................................... 240 4 54 Influence Ratio of alpha baseline ..................................................................... 240 5 1 Bond stress analysis ......................................................................................... 260 5 2 Test series 16 (unconfined setup) short term verification tests results with adhesive C in higher strength concrete at 110 F .............................................. 260 5 3 Test series 16 (unconfined setup) short term verification tests results with adhesive C in higher strength concrete at 80F ................................................ 261 5 4 Summary of alpha reduction factors per test series .......................................... 261 5 5 TS02B (US baseline B) load versus displacement plot .................................... 262 5 6 Typical ter minated sample for adhesive B ........................................................ 262 5 7 Typical terminated sample for adhesive C ........................................................ 263

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24 5 8 Typical adhesive bond failure ........................................................................... 263 5 9 Typica l shearing failure at threads .................................................................... 264 5 10 University of Florida computed tomography x ray system ................................ 264 5 11 Load versus displacement plot for x ray investigation short term load test stopped prior to failure ...................................................................................... 265 5 12 X ray scans of short term load test on adhesive B stopped prior to failure ....... 265 5 13 Displacement versus time plot for x ray investigation sustained load test on adhesive B stopped prior to failure ................................................................... 266 5 14 X ray scans of sustained load test on adhesive B stopped prior to failure ........ 266 5 15 Load versus displacement plot for x ray investigation short term load test on adhes ive B continued past failure ..................................................................... 267 5 16 X ray scans of short term load test on adhesive B continued past failure ........ 267 6 1 Baseline TS01B SvTTF plot with short term tests excluded from the projection .......................................................................................................... 290 6 2 Baseline TS01B SvTTF plot with short term tests included in the projection .... 290 6 3 Ratio of sustained load test failure displacements to short term test failure displacements for UF baselines ........................................................................ 291 6 4 Failure displacement versus timeto failure for all three UF baseline tests ....... 291 6 5 Failure displacement versus %MSL for all three UF baseline tests .................. 292 6 6 Combined baseline SvTTF for adhesive A normalized by the average bond stress of the short term tests from UF and US ................................................. 292 6 7 Combined baseline SvTTF for adhesive B normalized by the average bond stress of the short term tests from UF and US ................................................. 293 6 8 Combined baseline SvTTF for adhesive C normalized by the average bond stress of the short term tests from UF and US ................................................. 293 6 9 Influence Ratio of the alphabaseline stress at various lifetimes ...................... 294 6 10 Influence Ratio of alpha baseline stress at 15 years exposure to elevated temperature (75 years) ..................................................................................... 294 6 11 Influence Ratio of alpha baseline stress at various lifetimes with the alphareduction factor limited to a maximum value of 1 .............................................. 295

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25 6 12 Influence Ratio of alpha baseline stress at 15 years exposure to elevated temperature (75 years) with the alphareduction factor limited to a maximum value of 1 .......................................................................................................... 295 6 13 Influence Ratio of nominal stress at 15 years exposure to elevated temperature (75 years) with the alphareduction factor limited to a maximum value of 1 and assuming a CoV of 0.15 ............................................................ 296 6 14 Limitation of method 1 ...................................................................................... 296 6 15 Results of Monte Carlo simulation on the Influence Ratio of the nominal stress with alpha reduction factors limited to a maximum value of 1 ................ 297 6 16 Confidence level that the Influence Ratio of the nominal stress is less than 1 at 15 years exposure to elevated temperature (75 years) ................................ 297 7 1 Incremental load rate short term test on adhesive B ........................................ 305 7 2 Displacement rate versus stress level for various adhesive anchor systems ... 305 7 3 Finite element m esh ......................................................................................... 306 7 4 Enlarged view of finiteelement mesh ............................................................... 306 7 5 Shear stress distribution at various load levels for P EPA model ..................... 307 7 6 Shear stress distribution at 95% STL for P EPA and VEPA models ............... 307 7 7 Shear stress distribution at 80% STL for P EPA and VEPA models ............... 308 7 8 Shear stress distribution at 60% STL for P EPA and VEPA models ............... 308 7 9 Shear stress distribution at 40% STL for P EPA and VEPA models ............... 309 8 1 Shear strain a pproximation in anchor tests ...................................................... 315 8 2 Displacement of the adhesive near the top of the hole radially across the annular gap ....................................................................................................... 315 8 3 Distribution of strains along the depth of the hole as determined by finite element analysis ............................................................................................... 316 8 4 Creep compliance comparison between dogbone and anchor tests for adhesive A ........................................................................................................ 316 8 5 Creep compliance comparison between dogbone and anchor tests for adhesive B ........................................................................................................ 317

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26 8 6 Creep compliance comparison between dogbone and anchor tests for adhesive C ........................................................................................................ 317 8 7 SvTTF comparison between anchor pullout tests and dogbone tests for adhesive A ........................................................................................................ 318 8 8 SvTTF comparison between anchor pullout tests and dogbone tests for adhesive B ........................................................................................................ 318 8 9 SvTTF comparison between anchor pullout tests and dogbone tests for adhesive C ........................................................................................................ 319 9 1 Normalized bond stress (by 28 day value) versus concrete age ...................... 328 9 2 D21 C ST 4 showing failure surface of incompletely cured specimen .............. 328 9 3 D21 C ST 5 showing failure surface of fully cured specimen ........................... 329 9 4 ISAT 10 minute sample data and relative humidity for sides of hole and formed surface .................................................................................................. 329 9 5 Hardness, concrete compression strength, and split tensile strength versus concrete age ..................................................................................................... 330 A 1 Concrete mix design laboratory worksheet for UF:A 1 ..................................... 341 A 2 Co ncrete mix design laboratory worksheet for UF:A 2 ..................................... 342 A 3 Concrete mix design laboratory worksheet for UF:A 3 ..................................... 343 A 4 Concrete mix design laboratory worksheet for UF:B 1 ..................................... 344 A 5 Concrete mix design laboratory worksheet for UF:B 2 ..................................... 345 A 6 Concrete mix design laboratory worksheet for UF:B 3 ..................................... 346 A 7 Concrete mix design laboratory worksheet for UF:C 1 ..................................... 347 A 8 Concrete mix design laboratory worksheet for UF:C 2 ..................................... 348 A 9 Concrete mix design laboratory worksheet for UF:C 3 ..................................... 349 A 10 Concr ete mix design laboratory worksheet for UF:D 1 ..................................... 350 A 11 Concrete mix design laboratory worksheet for UF:D 2 ..................................... 351 A 12 Concrete mix design laboratory worksheet for UF:D 3 ..................................... 352 A 13 Concrete mix design laboratory worksheet for UF:E 1 ..................................... 353

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27 A 14 C oncrete mix design laboratory worksheet for UF:E 2 ..................................... 354 A 15 Concrete mix design laboratory worksheet for UF:E 3 ..................................... 355 A 16 Concrete mix design laboratory worksheet for UF:F 1 ..................................... 356 A 17 Concrete mix design laboratory worksheet for UF:F 2 ..................................... 357 A 18 Concrete mix design laboratory worksheet for UF:F 3 ..................................... 358 A 19 Concrete mix design laboratory worksheet for UF:G 1 ..................................... 359 A 20 Concrete mix design laboratory worksheet for UF:G 2 ..................................... 360 A 21 Concrete mix design laboratory worksheet for UF:G 3 ..................................... 361 A 22 Concrete mix design laboratory worksheet for UF:H 1 ..................................... 362 A 23 Concrete mix design laboratory worksheet for UF:H 2 ..................................... 363 A 24 Concrete mix design laboratory worksheet for UF:H 3 ..................................... 364 A 25 Concrete mix design laboratory worksheet for UF:I 1 ....................................... 365 A 26 Concrete mix design laboratory worksheet for UF:I 2 ....................................... 366 A 27 Concrete mix design laboratory worksheet for UF:I 3 ....................................... 367 A 28 Florida Rock concrete mix design for mix UF:G ............................................... 368 A 29 Florida Rock co ncrete mix design for mix UF:G ............................................... 369 B 1 Test specimen with PTFE sheet and confining plate installed .......................... 390 B 2 Transducer mount on top of the test specimen................................................. 390 B 3 Tripod on top of the test specimens .................................................................. 391 B 4 Hydraulic ram and load cell on top of the tripod ................................................ 392 B 5 Coupler installed between loading rod and anchor ........................................... 393 B 6 Transducer mount ............................................................................................ 393 B 7 Transducer mount and transducer installed ..................................................... 394 B 8 Illustration of the large heating chamber (containing three test rigs) ................ 394 B 9 Small heating chamber (containing a single test rig) ........................................ 395

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28 B 10 Disc spring package ......................................................................................... 395 B 11 Disc spring characteristics ................................................................................ 396 B 12 Loading system ................................................................................................ 396 B 13 Loa ding system installed .................................................................................. 397 B 14 Typical concrete test specimen ........................................................................ 397 B 15 Compression machine ...................................................................................... 398 B 16 Anchor showing 45 cone to fit into centering guide ......................................... 398 B 17 Climate chamber .............................................................................................. 399 B 18 Screenshot of NI DIAdem 10.2 data acquisition program ................................. 399 B 19 Sustained load test setup ................................................................................. 400 B 20 Drilling rig and hammer drill .............................................................................. 400 B 21 Vacuum adaptor ............................................................................................... 401 B 22 Centering tool ................................................................................................... 401 B 23 Cen tering tool inserted in hole .......................................................................... 402 B 24 Centering guide with anchor ............................................................................. 402 B 25 Anchor with centering ring ................................................................................ 403 B 26 Illustration of the test rig with a vertical cut ....................................................... 404 C 1 INSTRON tensile testing machine .................................................................. 418 C 2 The oven, which pulls forward around the INSTRON, used to keep the samples at temperature .................................................................................... 418 C 3 Test frames for sustained load dogbone testing ............................................... 419 C 4 Dogbone specimen loaded in grips .................................................................. 419 C 5 DSR machine ................................................................................................... 420 C 6 Silicon molds for casting dogbone specimens .................................................. 420 C 7 DMTA and DSR creep s pecimens .................................................................... 421 C 8 Left side of testing chamber ............................................................................. 421

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29 C 9 Right side of testing chamber ........................................................................... 422 C 10 Data sampling LabVIEW program .................................................................... 422 C 11 Sustained load test LabVIEW program (main screen) ...................................... 423 C 12 Sustained load test LabVIEW program (strain plot) .......................................... 423 D 1 TS01A UF baseline adhesive A short term load vs. displacement ................ 432 D 2 TS01A UF baseline adhesive A short term stress vs. displacement ............. 432 D 3 TS01A UF b aseline adhesive A late short term load vs. displacement ......... 433 D 4 TS01A UF baseline adhesive A late short term stress vs. displacement ....... 433 D 5 TS01B UF baseline adhesive B short term load vs. displacement ................ 434 D 6 TS01B UF baseline adhesive B short term stress vs. displacement ............. 434 D 7 TS01B UF baseline adhesive B late short term load vs. displacement ......... 435 D 8 TS01B UF baseline adhesive B late short term stress vs. displacement ....... 435 D 9 TS01C UF baseline adhesive C short term load vs. displacement ................ 436 D 10 TS01C UF baseline adhesive C short term stress vs. displacement ............. 436 D 11 TS02A US baseline adhesive A short term load vs. displacement ................ 437 D 12 TS02A US baseline adhesive A short term stress vs. displacement ............. 437 D 13 TS02A US baseline adhesive A late short term load vs. displacement ......... 438 D 14 TS02A US baseline adhesive A late short term stress vs. displacement ...... 438 D 15 TS02B US baseline adhesive B short term load vs. displacement ................ 439 D 16 TS02B US baseline adhesive B short term stress vs. displaceme nt ............. 439 D 17 TS02B US baseline adhesive B late short term load vs. displacement ......... 440 D 18 TS02B US baseline adhesive B late short term stress vs. displacement ...... 440 D 19 TS02C US baseline adhesive C short term load vs. displacement ................ 441 D 20 TS02C US baseline adhesive C short term stress vs. displacement ............. 441 D 21 TS03B 120 F service temperature short term load vs. displacement ............ 442

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30 D 22 TS03B 120 F service temperature short term stress vs. displacement ......... 442 D 23 TS04B 70 F service temperature short term load vs. displacement .............. 443 D 24 TS04B 70 F service temperature short term stress vs. displacement ........... 4 43 D 25 TS05A horizontal installation short term load vs. displacement ..................... 444 D 26 TS05A horizontal installation short term stress vs. d isplacement .................. 444 D 27 TS06A overhead installation short term load vs. displacement ..................... 445 D 28 TS06A overhead installation short term stress vs. displacement .................. 445 D 29 TS07A moisture at installation short term load vs. displacement .................. 446 D 30 TS07A moisture at installation short term stress vs. displacement ................ 446 D 31 TS07B moisture at installation short term load vs. displacement .................. 447 D 32 TS0 7B moisture at installation short term stress vs. displacement ................ 447 D 33 TS07C moisture at installation short term load vs. displacement .................. 448 D 34 TS07C moisture at installation short term stress vs. displacement ............... 448 D 35 TS08B moisture during installation short term load vs. displacement ........... 449 D 36 TS08B moisture during installation short term stress vs. displacement ......... 449 D 37 TS09A partially cleaned hole short term load vs. displacement .................... 450 D 38 TS09A partially cleaned hole short term stress vs. displacement .................. 450 D 39 TS09B partially cleaned hole short term load vs. displacement .................... 451 D 40 TS09B partially cleaned hole short term stress vs. displacement .................. 451 D 41 TS09C partially cleaned hole short term load vs. displacement .................... 452 D 42 TS09C partially cleaned hole short term stress vs. displacement ................. 452 D 43 TS10A MFR minimum installation temperature/MFR minimum service temperature short term load vs. displacement .................................................. 453 D 44 TS10A MFR minimum installation temperature/MFR minimum service temperature short term stress vs. displacement ............................................... 453

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31 D 45 TS11A MFR minimum installation temperature/110F service temperature short term load vs. displacement ...................................................................... 454 D 46 TS11A MFR minimum installation temperature/110F service temperature short term stress vs. displacement ................................................................... 454 D 47 TS12A DOT concrete mix short term load vs. displacement ......................... 455 D 48 TS12A DOT concrete mix short term stress vs. displacement ...................... 455 D 49 TS12B DOT concrete mix short term load vs. displacement ......................... 456 D 50 TS12B DOT concrete mix short term stress vs. displacement ...................... 456 D 51 TS12C DOT concrete mix short term load vs. displacement ......................... 457 D 52 TS12C DOT concrete mix short term stress vs. displacement ...................... 457 D 53 TS13A core drilled hole short term load vs. displacement ............................. 458 D 54 TS13A core drille d hole short term stress vs. displacement .......................... 458 D 55 TS13B core drilled hole short term load vs. displacement ............................. 459 D 56 TS13B core drilled hole short term stress vs. displacement .......................... 459 D 57 TS13C core drilled hole short term load vs. displacement ............................ 460 D 58 TS13C core drilled hole short term stress vs. displacement .......................... 460 D 59 TS14A fly ash mix short term load vs. displacement ..................................... 461 D 60 TS14A fly ash mix short term stress vs. displacement .................................. 461 D 61 TS14B fly ash mix short term load vs. displacement ..................................... 462 D 62 TS14B fly ash mix short term stress vs. displacement .................................. 462 D 63 TS14C fly ash mix short term load vs. displacement ..................................... 463 D 64 TS14C fly ash mix short term stress vs. displacement .................................. 463 D 65 TS15A blast furnace slag mix short term load vs. displacement ................... 464 D 66 TS15A blast furnace slag mix short term stress vs. displacement ................. 464 D 67 TS15B blast furnace slag mix short term load vs. displacement ................... 465 D 68 TS15B blast furnace slag mix short term stress vs. displacement ................. 465

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32 D 69 TS15C blast furnace slag mix short term load vs. displacement ................... 466 D 70 TS15C blast furnace slag mix short term stress vs. displacement ................ 466 D 71 TS16A unconfined setup mix short term load vs. displacement .................... 467 D 72 TS16A unconfined setup mix short term stress vs. displacement ................. 467 D 73 TS16B unc onfined setup mix short term load vs. displacement .................... 468 D 74 TS16B unconfined setup mix short term stress vs. displacement ................. 468 D 75 TS16C unconfined setup mix short term load vs. displacement .................... 469 D 76 TS16C unconfined setup mix short term stress vs. displacement ................. 469 D 77 TS21A adhesive alone dogbone baseline adhesive A short term stress vs. strain ................................................................................................................. 470 D 78 TS21B adhesive alone dogbone baseline adhesive B short term stress vs. strain ................................................................................................................. 470 D 79 TS21C adhesive alone dogbone baseline adhesive C short term stress vs. strain ................................................................................................................. 471 D 80 TS22A manufacturer cure time short term stress vs. strain ........................... 471 D 81 TS22B manufacturer cure time short term stress vs. strain ........................... 472 G 1 TS01A UF baseline adhesive A creep displacement vs. time ........................ 487 G 2 TS01B UF baseline adhesive B creep displacement vs. time ........................ 488 G 3 TS01C UF baseline adhesive C creep displacement vs. time ........................ 488 G 4 TS02A US baseline adhesive A creep displacement vs. time ........................ 489 G 5 TS02B US baseline adhesive B creep displacement vs. time ........................ 489 G 6 TS02C US baseline adhesive C creep displacement vs. time ........................ 490 G 7 TS03B 120F service temperature creep displacement vs. time ................... 490 G 8 TS04B 70F service temperature creep displacement vs. time ..................... 491 G 9 TS05A horizontal installation creep displacement vs. time ............................ 491 G 10 TS06A overhead installation creep displacement vs. time ............................ 492

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33 G 11 TS07A moisture at installation creep displacement vs. time .......................... 492 G 12 TS08B moisture during service creep displacement vs. time ........................ 493 G 13 TS09C partially cleaned hole creep displacement vs. time ........................... 493 G 14 TS10A MFR minimum installation temperature/ MFR minimum service temperature creep displacement vs. time ......................................................... 494 G 15 TS11A MFR minimum installation temperature/110F service temperature creep displacement vs. time ............................................................................. 494 G 16 TS12A DOT concrete mix creep displacement vs. time ................................ 495 G 17 TS13B core drilled hole creep displacement vs. time .................................... 495 G 18 TS14B fly ash creep displacement vs. time ................................................... 496 G 19 TS15A blast furnace slag creep displacement vs. time ................................. 496 G 20 TS16C unconfined setup creep displacement vs. time .................................. 497 H 1 TS 01A Stress versus Timeto Failure Report .................................................. 498 H 2 TS 01B Stress versus Timeto Failure Report .................................................. 499 H 3 TS 01C Stress versus Timeto Failure Report .................................................. 500 H 4 TS 02A Stress versus Timeto Failure Report .................................................. 501 H 5 TS 02B Stress versus Timeto Failure Report .................................................. 502 H 6 TS 02C Stress versus T ime to Failure Report .................................................. 503 H 7 TS 03B Stress versus Timeto Failure Report .................................................. 504 H 8 TS 04B Stress versus Timeto Failure Report .................................................. 505 H 9 TS 05A Stress versus Timeto Failure Report .................................................. 506 H 10 TS 06A Stress versus Timeto Failure Report .................................................. 507 H 11 TS 07A Stress versus Timeto Failure Report .................................................. 508 H 12 TS 08B Stress versus Timeto Failure Report .................................................. 509 H 13 TS 09C Stress versus Timeto Failure Report .................................................. 510 H 14 TS 10A Stress versus Timeto Failure Report .................................................. 511

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34 H 15 TS 11A Stress versus Timeto Failure Report .................................................. 512 H 16 TS 12A Stress versus Timeto Failure Report .................................................. 513 H 17 TS 13B Stress versus Timeto Failure Report .................................................. 514 H 18 TS 14B Stress versus Timeto Failure Report .................................................. 515 H 19 TS 15A Stress versus Timeto Failure Report .................................................. 516 H 20 TS 16A Stress versus Timeto Failure Report .................................................. 517 H 21 TS 21A Stress versus Timeto Failure Report .................................................. 518 H 22 TS 21B Stress versus Timeto Failure Report .................................................. 519 H 23 TS 21C Stress versus Timeto Failure Report .................................................. 520 H 24 TS 22A Stress versus Timeto Failure Report .................................................. 521 I 1 DMTA test results for adhesive A ..................................................................... 531 I 2 DMTA test results for adhesive B ..................................................................... 531 I 3 DMTA test results for adhesive C ..................................................................... 532 I 4 Adhesive A baseline strain vs. time plot for dogbone specimens ..................... 532 I 5 Adhesive B baseline strain vs. time plot for dogbone specimens ..................... 533 I 6 Adhesive C baseline strain vs. time plot for dogbone specimens ..................... 533 I 7 Adhesive A baseline compliance vs. time plot for dogbone specimens ............ 534 I 8 Adhesive B baseline compliance vs. time plot for dogbone specimens ............ 534 I 9 Adhesive C baseline compliance vs. time plot for dogbone specimens ............ 535 I 10 Compliance versus time plot for DSR creep test of adhesive A at different temperatures .................................................................................................... 535 I 11 Shifted master compliance curve for adhesive A using 43C as a reference temperature ...................................................................................................... 536 I 12 Comparison between predicted compliance from the DSR creep test and the sustained load creep tests on dogbone samples for adhesive A ...................... 536 I 13 Compliance versus time plot for DSR creep test of adhesive B at different temperatures .................................................................................................... 537

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35 I 14 Shifted master compliance curve for adhesive B using 43C as a reference temperature ...................................................................................................... 537 I 15 Comparison between predicted compliance from the DSR creep test and the sustained load creep tests on dogbone samples for adhesive B ...................... 538 I 16 Compliance versus time for the DSR creep test of adhesive B at different stress levels ...................................................................................................... 538 I 17 Shifted master compliance curve for adhesive B using 72.5 psi (0.5 MPa) as the reference stress .......................................................................................... 539 I 18 Shifted factor as a function of compliance for each pair of compliance creep curves for adhesive B at different stresses for short term DSR creep tests ..... 539 I 19 Shifted factor for adhesive B as a function of compliance for each pair of compliance creep curves at different stresses for the sustained load c ree p ..... 540 I 20 Difference in stress vs. the slope of the fit for each of the plots from Figure I 19. .................................................................................................................. 541 I 21 Compliance versus time for DSR creep test of adhesive C at different temperatures .................................................................................................... 541 I 22 Shifted master compliance curve for adhesive C using 43C as reference temperature ...................................................................................................... 542 I 23 Comparison between predicted compliance from the DSR creep test and sustained load creep tests on dogbone specimens for adhesive C .................. 542 I 24 Comparison between predicted compliance from the DSR creep test and sustained load creep tests on dogbone specimens for adhesive C with higher curing temperature ........................................................................................... 543 J1 Early age concrete short term load versus displacement results for adhesive A at 4 days ........................................................................................................ 546 J2 Early age concrete short term stress versus displacement results for adhesive A at 4 days ........................................................................................ 546 J3 Early age concrete short term load versus displacement results for adhesive B at 4 days ........................................................................................................ 547 J4 Early age concrete short term stress versus displacement results for adhesive B at 4 days ........................................................................................ 547 J5 Early age concrete short term load versus displacement results for adhesive C at 4 days ....................................................................................................... 548

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36 J6 Early age concrete short term stress versus displacement results for adhesive C at 4 days ........................................................................................ 548 J7 Early age concrete short term load versus displacement results for adhesive A at 7 days ........................................................................................................ 549 J8 Early age concrete short term stress versus displacement results for adhesive A at 7 days ........................................................................................ 549 J9 Early age concrete short term load versus displacement results for adhesive B at 7 days ........................................................................................................ 550 J10 Early age concrete short term stress versus displacement results for adhesive B at 7 days ........................................................................................ 550 J11 Early age concrete short term load versus displacement results for adhesive C at 7 days ....................................................................................................... 551 J12 Early age concrete short term stress versus displacement results for adhesive C at 7 days ........................................................................................ 551 J13 Early age concrete short term load versus displacement results for adhesive A at 14 days ...................................................................................................... 552 J14 Early age concrete short term stress versus displacement results for adhesive A at 14 days ...................................................................................... 552 J15 Early age concrete short term load versus displacement results for adhesive B at 14 days ...................................................................................................... 553 J16 Early age concrete short term stress versus displacement results for adhesive B at 14 days ...................................................................................... 553 J17 Early age concrete short term load versus displacement results for adhesive C at 14 days ..................................................................................................... 554 J18 Early age concrete short term stress versus displacement results for adhesive C at 14 days ...................................................................................... 554 J19 Early age concrete short term load versus displacement results for adhesive A at 21 days ...................................................................................................... 555 J20 Early age concrete short term stress versus displacement results for adhesive A at 21 days ...................................................................................... 555 J21 Early age concrete short term load versus displacement results for adhesive B at 21 days ...................................................................................................... 556

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37 J22 Early age concrete short term stress versus displacement results for adhesive B at 21 days ...................................................................................... 556 J23 Early age concrete short term load versus displacement results for adhesive C at 21 days ..................................................................................................... 557 J24 Early age concrete short term stress versus displacement results for adhesive C at 21 days ...................................................................................... 557 J25 Early age concrete short term load versus displacement results for adhesive A at 28 day s...................................................................................................... 558 J26 Early age concrete short term stress versus displacement results for adhesive A at 28 days ...................................................................................... 558 J27 Early age concrete short term load versus displacement results for adhesive B at 28 days ...................................................................................................... 559 J28 Early age concrete short term stress versus displacement results for adhesive B at 28 days ...................................................................................... 559 J29 Early age concrete short term load versus displacement results for adhesive C at 28 days ..................................................................................................... 560 J30 Early age concrete short term stress versus displacement results for adhesive C at 28 days ...................................................................................... 560

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38 LIST OF ABBREVIATION S AASHTO American Association of State Highway and Transportation Officials ACI American Concrete Institute ASD Allowable Stress Design ASTM American Society for Testing and Materials CALTRANS California Department of Transportation CAMA Concrete Anchor Manufacturers Association CRSI Concrete Reinforcing Steel Institute DIN Deutsches Institute fr Normung DMTA Dynamic Mechanical Thermal Analysis DSR Dynamic Shear Rheometer EOTA European Organisation for Technical Approvals ESR Evaluation Safety Report ETAG European Technical Approval Guideline FDOT Florida Department of Transportation fib Federation Internationale du Beton ICCES International Code Council Evaluation Service IDOT Illinois Department of Transportation IS AT Initial Surface Absorption Test IWB Institut fr Werkstoffe im Bauwesen LRFD Load and Resistance Factor Design MDOT Michigan Department of Transportation MPII Manufacturers Printed Installation Instructions MSL Mean Short term Load NCHRP National Cooperative Highway Research Program

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3 9 NI National Instruments NIST National Institute of Standards and Technology NTSB National Transportation Safety Board NYSDOT New York State Department of Transportation PENNDOT Pennsylvania Department of Transportation PTFE Polytetrafluoroethylene RH Relative Humidity SvTTF Stress versus Time to Failure TxDOT Texas Department of Transportation UF University of Florida US University of Stuttgart VDOT Virginia Department of Transportation WSDOT Washington State Department of Tr ansportation

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40 Abstract of Dissertation Presented to the Graduate School of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy SUSTAINED LOAD PERFORMANCE OF ADHESIVE ANCHOR SYSTEMS I N CONCRETE By Todd Marshall Davis August 2012 Chair: Ronald A. Cook Major: Civil Engineering Stemming from a tragic failure of an adhesive anchor system this research project investigated the sustained load performance of adhesive anchors in concrete under different installat ion and inservice conditions. The literature review investigated the current state of art of adhesive anchors. Extensive discussion was devoted to the behavior of adhesiv e anchors in concrete as well as the many factors that can affect their short term and sustained load strength. Existing standards and specifications for the testing, design, construction, and inspection of adhesive anchors were covered. Based on the results of the literature review and the experience of the research group, a triage was conducted on many parameters identified as possibly affecting the sustained load performance of adhesive anchors and the highest priority parameters were investigated i n this project. A stress versus timeto failure approach was used to evaluate sensitivity of three ICC ES AC 308 approved adhesive anchor systems Of the various parameters investigated, only elevated inservice temperature and manufacturers cure time w as shown to exhibit adverse effects on sustained loads more

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41 than that predicted by short term tests of fully cured adhesive over a reasonable structure lifetime of 75 years. In a related study, various tests were conducted on the adhesive alone (timetemperature superposition, timestress superposition, and dogbone tensile tests). The results of that study were used to investigate the existence of a correlation with long term anchor pullout testing in concrete. No consistent correlations were detected for the adhesives in the study. Tests were also conducted on the effect of early age concrete on adhesive anchor bond strength. O n the basis of confined test bondstrength alone, adhesive A (vinyl ester) did not show any significant increase after 14 days (102% of 28 day strength at 14 days), and adhesive B and C (epoxies) did not show any significant increase after 7 days (104% and 93% of 28 days strength at 7 days respectively). The results of this research were used to draft recommended standards and specifications for AASHTO pertaining to testing, design, construction, and inspection of adhesive anchors in concrete for transportation structures. These draft standards we re not i ncluded in this dissertation.

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42 CHAPTER 1 BACKGROUND Introduction The primary objective of this research was to i nvestigate the influence of various parameters (e.g., type of adhesive, installation conditions, and inservice conditions) on the sustained load performance of adhesive anchors. The results of this study were used to develop recommended test methods, mat erial specifications, design guidelines, design specifications, quality assurance guidelines and construction specifications for AASHTO for the use of adhesive anchors in transportation structures. These draft standards and specifications are included in a separate NCHRP report. This chapter presents a brief overview of the background of the behavior and design of adhesive anchors in concrete Background on Behavior/ Design of Anchors While various design standards and design methodology will be discussed i n detail later, a general review of the current behavior/design for anchoring to concrete is provided for background. This document adopts the definition of adhesive as found in ACI 355.411, which is as follows: Adhesive Any adhesive comprised of chemical components that cure when blended together. Adhesives are formulated from organic polymers, or a combination of organic polymers and inorganic materials. Organic polymers used in adhesives can include, but are not limited to, epoxies, polyurethanes, polyesters, methyl methacrylates and vinyl esters. Behavioral Model The behavioral model and resulting design procedures for adhesive anchors contained in most standards have been under development for the past twenty years.

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43 Detailed information on s ingle adhesive anchor behavior is presented in Cook et al. (1998). Information on group and edge effects is presented in Eligehausen et al. (2006a). The following presents a general overview of the behavior/design model for single adhesive anchors. Figure 11 shows typical failure modes exhibited by bonded anchors. Figure 12 shows the mechanism for load transfer in bonded anchors. In the elastic range, adhesive anchors have been shown in Cook et al. (1993) to exhibit a hyperbolic tangent stress distribution along the bonded anchor as shown in Figure 1 3 Research by McVay et al. (1996) used an elastoplastic Sandler DiMaggio constitutive model to show how the bond stress is distributed along the length of anchor under various stress levels ( Figure 14 Figure 17 ). Figure 14 Figure 17 have been modified from their original in that the percent stress level has been identified for each curve. At low load levels, the stress distribution generally follows the elastic hyperbolic tangent stress distribution in which the adhesive close to the surface is higher stressed than the adhesive deeper in the hole. As the load level is increased above ~30% of the peak stress, the upper portions of the adhesive become plastic and redistribute the load further into the hole. As the load is fur ther increased, deeper and deeper portions of the adhesive become plastic. As the stress level reaches approximately 70% of the peak stress, the stress distribution approaches a relatively uniform bond stress distribution along the entire length of the anchor. Any additional increase in load causes the adhesive to dilate providing for an increased capacity until failure. For adhesive bonded anchors where the hole diameter does not exceed 1.5 times the anchor diameter and with an embedment depth to anchor diameter ratio not

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44 exceeding 20, the uniform bond stress model shown in Figure 1 8 and given by Equation 11 has been shown to be a valid behavioral model both experimentally and numerically (Cook et al. (1998)). In Equation 11 the mean failure load ( ) is a function o f the product s mean bond strength ( ) multiplied by the bond area calculated at the anchor diameter ( d ). As noted in Cook et al. (1998), test samples in a worldwide database indicated that the hole size is less than 1.5 times the anchor diameter for adh esive anchor applications. Anchors in holes larger than 1.5 times the anchor diameter typically use cementitious or polymer grout. For these typical adhesive anchor applications with hole sizes less than 1.5 times the anchor diameter, it is not practical to establish two separate interface bond strengths as shown in Figure 12 and test data shows that the uniform bon d stress model works quite well if the bond stress is determined from a series of product qualification tests by simply dividing the failure load by the bonded area calculated at the diameter of the anchor. Details of this are provided in Cook et al. (1998). = (1 1) where: mean failure load, lb mean bond strength, psi d anchor diameter, in h ef embedment depth, in For design, the nominal bond strength of adhesive bonded anchors is dependent on the mean bond strength of anchors installed in accordance with the Manufacturers Printed Installation Instructions (MPII), adjusted for scatter of the products test results, and for the products sensitivity to installation and inservice conditions. As discussed in

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45 Cook and Konz (2001) the bond strength of proper ly installed bonded anchor products varies considerably. Based on tests of twenty adhesive anchor products, the mean bond strength at the adhesive/anchor interface for individual products ranged from 330 psi to 2,830 psi (2.3 MPa to 19.5 MPa). Current adhesive anchor products can reach bond strengths above 4,000 psi (27.6 MPa). Short term Sensitivity The short term load sensitivity of an adhesive to a specific variable can be determined from two series of short term tests. A series of five baseline tests are conducted to determine the adhesives short term strength under standard conditions ( ). Another series of five tests are conducted with a specific variable introduced ( ). The reduction factor ( ) is determined by dividing the average load of the variable test by the average load of the baseline test. This is illustrated in Figure 19 Equation 12 provides the basic design relationship using LRFD for a single adhesive anchor. As shown by Equation 12 the factored tension load ( Nu) must be less than the design strength determined as a capacity reduction factor () multiplied by the nominal bond capacity. (1 2) where: N u factored tension load, lb capacity reduction factor nominal bond stre ngth psi d anchor diameter, in h ef embedment depth, in

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46 The nominal bond strength ( ) is the 5% lower fractile of the mean bond strength ( ) adjusted by a series of reduction factors ( ) for installation and inservice conditions as shown in Equation 1 3 = (1 3) where: 5% lower fractile of mean bond strength reduction factors determined from comparing the bond strength under different installation and inservice conditions to the baseline bond strength The 5% lower fractile, or characteristic value, ( ) is determined from Equation 14 : = ( 1 ) (1 4) where: mean bond stress, psi K tolerance factor corresponding to a 5% probability of non exceedence with a 90% confidence using ACI 355.411. Note, other definitions of characteristic value exist. For e xample ASTM D729 0 uses an 80% confidence interval. coefficient of variation Sustained L oad Influence The single anchor design model is provided for reference. Recommendations on how to incorporate the effects of sustained load performance under various installation and inservice conditions are addressed in this project. For parameters that are shown to have a more aggravated effect under sustained load than under short term load, a red uction factor ( ) would be dependent on stress level and duration of load. This relationship can be determined from the stress versus timeto failure test series discussed later.

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47 Summary This chapter provided an overview of the behavior of adhesive anch ors and the subsequent uniform bond stress design approach. An introduction to the methodology to evaluate the sensitivity of an adhesive anchor system to short term and sustained loading was discussed. C hapter 2 presents the literature review on adhesiv e anchor performance under various installation and inservice conditions as well as how various state, national, and international agencies address testing, design, construction, and inspection of adhesive anchor systems.

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48 concrete breakout failure mortar/concrete interface steel/mortar interface mortar/concrete and steel/mortar interface Figure 1 1 Potential embedment failure modes of bonded anchors [Reprinted with permission from Cook, R.A., Kunz, J., Fuchs, W., and Konz, R.C. (1998). Behavior and Design of Single Adhesive Anchors Under Tensile Load in Uncracked Concrete. ACI Structural Journal 95(1), pp. 926. ] Figure 1 2 Mechanism of load transfer of a bonded anchor

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49 Figure 1 3 Hyperbolic tangent stress distribution Figure 1 4 Stress distribution along length of adhesive anchor for hef/do = 4.00 [Reprinted, with permission, from McVay, M., Cook, R.A., Krishnamurthy, K. (1996). Pullout Simulation of Postinstalled Chemically Bondaed Anchors. Journal of Structural Engineering, ASCE, 122(9), 10161024. ] Figure 1 5 Stress distribution along length of adhesive anchor for hef/do = 5.33 [Reprinted, with permission, from McVay, M., Cook, R.A., Krishnamurthy, K. (1996). Pullout Simulation of Postinstalled Chemically Bondaed Anchors. Journal of Structural Engineering, ASCE, 122(9), 10161024. ]

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50 Figure 1 6 Stress distribution along length of adhesive anchor for hef/do = 6.67 [Reprinted, with permission, from McVay, M., Cook, R.A., Krishnamurthy, K. (1996). Pullout Simulation of Postinstalled Chemically Bondaed Anchors. Jou rnal of Structural Engineering, ASCE, 122(9), 10161024. ] Figure 1 7 Stress distribution along length of adhesive anchor for hef/do = 8.00 [Reprinted, with permission, from McVay, M., Cook, R.A., Krishnamurthy, K. (1996). Pullout Simulation of Postinstalled Chemically Bondaed Anchors. Journal of Structural Engineering, ASCE, 122(9), 10161024. ] Figure 1 8 Uniform bond stress model for adhesive ancho rs

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51 Figure 1 9 Calculation of short term

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52 CHAPTER 2 LITERATURE REVIEW This chapter presents the literature review on adhesive anchor performance under various installation and inservice conditions as well as how various state, national, and international agencies address testing, design, construction, and inspection of adhesive anchor systems. Parameters I nfluencing B ond S trength As noted in Cook et al. (1994), Cook et al. (1996), and Cook and Konz (2001) there are many variables that affect the performance of adhesive anchors. Below is a list of many of the common factors with brief comments with a more in depth discussion following Most of the items in the list are incor porated into ICC ES AC308 ACI 355.411, and EOTA (2002) discussed later in this chapter. In Service Factors Elevated Temperature: temperature variations during the life of the structure, and effects of sustained elevated temperature. Reduced Temperature: brittleness associated with reduced temperature Moisture in Service: adhesive anchor subjected to dry, damp, or immersed conditions during the life of the anchor. Freeze Thaw: magnitude and frequency of freeze thaw cycles. Factors Rel ated to the Adhesive Type of Adhesive: for example: epoxy mercaptan, epoxy amine, vinylester, polyester, or hybrid. Mixing Effort: how well the constituent parts are mixed prior to installation Adhesive Curing Time When First Loaded: 24 hours, 7 days, 28 days, or longer. Bond Line Thickness: how much space is there between the anchor and the sides of the hole

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53 Fiber Content of Adhesive: type and proportion of fillers in the adhesive Chemical Resistance: alkalinity, sulfur dioxide, and other compounds Install ation Factors Hole Orientation: downward, horizontal, upward. Hole Drilling: rotary hammer, core drill, or drilled in accordance with manufacturers instructions Hole Cleaning: uncleaned, partially cleaned, or cleaned in accordance with the manufacturers instructions Moisture in Installation: dry, damp, submerged, or installed in holes with moisture limitation conditions in accordance with manufacturers instructions. Installation Temperature: concrete at low temperature, adhesive at low temperature or pr eheated. Depth of Hole (Embedment Depth): the depth of the anchor can affect not only the bond strength but the type of failure. Anchor Diameter. anchor diameter can affect bond strength. Type of Concrete: Portland cement only, Portland cement with blast furnace slag, fly ash, or other additives. Concrete Strength: low compressive strength, high compressive strength Type of Coarse Aggregate: mineralology, absorption, and hardness (affects hole roughness) Cracked or Uncracked Concrete: the presence of crack s can reduce the bond strength significantly. Concrete Age: installed and/or loaded at early age In Service F actors Elevated t emperature. According to Messler (2004), the greatest shortcoming of many structural adhesives is their limited tolerance of elevated temperature. However, adhesives with openring structures (polyimidazoles and substituted imidazoles) that close under high temperatures become stronger. He further adds that it is important to

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54 measure an adhesives resistance to creep under sustained loading conditions especially if exposed to high temperature. According to Adams and Wake (1984), an adhesive anchor system with sus tained loads at a temperature 18F (10C) above its heat deflection temperature will exhibit significant creep. Experimental tests by CALTRANS in Dusel and Mir (1991) confirm this and explain that the adhesive will soften and become rubbery above its gl ass transition temperature (comparable to heat deflection temperature) and its bond strength will decrease. Reduced t emperature. Reduced inservice temperatures can make adhesives more brittle as mentioned in Cognard (2005) Currently ICCES AC308 has a reduced temperature test only during installation. The commentary for ACI 355.411 mentions that reduced temperature during installation increases viscosity and retards the cure time of adhesives. Moisture in s ervice. While it has been widely know n that the presence of moisture during the installation of the adhesive affects bond strength, a study by Chin et al. (2007) indicates that the presence of moisture after curing can also affect the creep resistance of an anchor. Chin et al. (2007) of the National Institute of Standards and Technology (NIST) conducted thermoviscoelastic analysis on ambient cure epoxy adhesives used in construction. This research showed that the presence of absorbed moisture after curing can create the same creep type behavior commonly seen in high temperature conditions. Cognard (2005) mentions that water can degrade adhesives in three ways: Penetrate into the adhesive and soften it.

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55 Penetrate between the adhesive and the substrate thereby destroying the adhesion. Penetrat e into porous substrates causing swelling and detrimental movements. Additionally, Cognard (2005) recommends that water resistance tests be performed if the bonds will be subject ed to moisture during the service life. Freeze t haw. The expansion and contraction of materials due to temperature changes and the expansion of water when it freezes tend to be detrimental to structural systems. Factors R elated to the A dhesive Type of a dhesive. According to Cook and Konz (2001) adhesives can vary significantly bet ween chemical groups and even within chemical groups. For example, on average, epoxy based adhesives have higher bond strengths than ester based adhesives. ASTM C881/C881M classifies seven types of epoxy resin bonding systems specifying Type IV as those t hat are for use in load bearing applications for bonding hardened concrete to other materials, but is not specifically identified for epoxies used in adhesive anchor systems. Fourier Transform Infrared Spectroscopy (FTIR) is a test method to chemically cha racterize an adhesive as shown in the NTSB (2007b) report on the adhesives from the Boston Tunnel collapse. The results of an FTIR test can be used to investigate correlations in the chemical makeup of an adhesive and its bond strength. ACI 355.411 includes several fingerprinting tests (discussed later) to identify the material and compare it against the manufacturers standard.

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56 Mixing e ffort. Bond strength is dependent on the proper composition of the adhesive. Adhesive anchor systems come in components that need to be mixed thoroughly and to the proper proportions prior to installation. Some systems are designed to guarantee proper proportions and thorough mixing, and some are solely dependent on the installer. Common systems include: Glass and Foil Capsule Systems which contain specific amounts of polymer resin, accelerator, and a mineral aggregate. The capsules are placed in the hole and an anchor (with a chiseled end) is set with a hammer drill which bores through the capsule thereby mixing the adhesive. See Figure 2 1 for a typical capsule anchor system. Injection Systems typically include plastic tubes of resin and hardener. The components are commonly mixed in a special nozzle as they are dispensed. The adhesive is injected into the hole and the anchor is installed afterwards. The anchor is usually rotated slowly during installation to prevent the formation of air bubbles which cause voi ds in the adhesive. See Figure 2 2 for a typical injection anchor system. Other Systems include pouches that contain the components which are mixed manually and then dispensed into the hole. It is also possible to purchase the components separately and mix them manually. Whichever system is used, it is important that the components are mixed thoroughly and to the proper proportions. Manufacturers ty pically recommend mixing until a certain consistency and color is reached. The adhesive must completely fill any voids between the anchor and the sides of the holes as any voids will reduce the effective area and subsequently the bond stress. Adhesive c ur ing t ime w hen f irst l oaded. According to Cook and Konz (2001), the duration of adhesive curing affects bond strength. Adhesives were tested at 24 hours and seven days of cure time. Most anchors showed a decrease in bond strength over a shorter adhesive cure time; the average bond strength for a 24 hour cure was 88% of those with a seven day cure.

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57 Bond l ine t hickness. According to olak (2007), the smaller the dimension between the anchor and the side of the hole, the lower the potential for creep. olak (2007) conducted tests on anchors with a ratio of the hole diameter to the anchor diameter ( do/d ) range of 1.2 to 1.8. In these tests, it was noticed that creep resistance was increased when the bond line thickness of the adhesive was decreased. This r elationship is supported by ACI 503.5R 92 2.3.7. However, according to analytical studies by Krishnamurthy (1996), anchors with a much larger ratio of the hole diameter to the anchor diameter ( do/d ) range of 1.2 to 4.1, the bond line thickness does not si gnificantly affect the capacity of the anchor. Therefore, current data is not conclusive. Fiber c ontent of a dhesive. ACI 503.5R 92 2.3.7 and olak (2001) mention that creep resistance can be increased by increasing the fiber content of the adhesive. Chemical r esistance. Cognard (2005) confirms that chemicals, oils, greases and other compounds can penetrate the adhesive and degrade the adhesion with the anchor or the concrete causing a bond failure. Installation F actors Hole o rientation. Hole orientation has the potential to significantly affect the performance of adhesive anchors. Vertical or upwardly inclined holes prove difficult to fill with adhesive, as the adhesive will tend to run out of the hole. The subsequent voids reduce the bond area between the adhesive and the anchor and/or the concrete and a smaller bond area reduces bond strength. Per FDOT (2009) 1.6 and FDOT ( 2007 ) 937 FDOT prohibits adhesive anchors to be installed in overhead or upwardly inclined holes for the above ment ioned reason. New York and Pennsylvania Departments of Transportation have similar restrictions.

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58 From the Boston Tunnel Collapse Investigation, NTSB (2007a) prohibits Departments of Transportation to use adhesive anchors in sustained tensileload overhea d highway applications until the development of testing and protocols to ensure safety. Due to the sensitivity to horizontal or vertically upward installed anchors to improper installation, ACI 355.411 requires that products be specifically approved for u se in these conditions and be installed by certified personnel. The ACI CRSI Adhesive Anchor Installation Certification Program includes both a written and performance evaluation which includes installation in vertically upward holes. Hole d rilling. The two common methods of hole drilling involve diamond core drill bits which produce very smooth sided holes or carbidetipped hammer drill bits which produce rough sided holes. Part of the adhesive bond with the concrete is composed of mechanical interlock and it was thought that a rough sided hole should provide better bond. This research project showed that for the three adhesives tested, an anchor installed in a core drilled hole had an average strength of 74% of an anchor installed in a rotary impact hammer drilled hole. Hole c leaning. According to Cook and Konz (2001) the cleanliness of the hole has a significant impact on bond stre ngth as dust created during the drilling operation can interfere with the adhesive/concrete bond surface. Tests were perf ormed in which some holes were cleaned with compressed air and a nonmetallic brush. Uncleaned holes had an average bond stress that was 71% of the cleaned holes (with a range from approximately 20% 150%) with a coefficient of variation of 20%.

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59 B rush ty pe is also significant. FDOT (2007) 416 requires cleaning with a nonmetallic brush, as metallic brushes tend to polish the sides of the holes thereby reducing the ability of the adhesive to create a mechanical interlock with the sides of the hole. Moisture in i nstallation. According to Cook and Konz (2001) the dampness of the hole significantly affects bond strength in two ways. It can restrict the entrance of the adhesive into the pores of the concrete thereby reducing mechanical interlock, and moist ure can interfere with the chemical reaction between the hardener and the resin. It was demonstrated by Cook and Konz (2001) that anchors installed in damp holes (wet surface) produced an average bond strength for 20 products of 77% (with a range of approx imately 20% to 150%) compared to a dry installation. Anchors installed in wet holes (standing water) produced an average bond strength of 43% (with a range of approximately 10% to 160%) compared to the dry installation. Installation t emperature. For anch ors installed at low temperatures, the final degree of hardening is smaller compared to installation at normal temperature. This might result in a reduction of the sustained load bond strength. Depth of h ole ( e mbedment d epth). Increasing the depth of the hole does have a slight impact on bond strength up to a point. According to tests by Krishnamurthy (1996), the load increases proportionally up to a limit of hef/d of 25 and then drops due to the bond stress not redistributing uniformly at depths greater than 25hef. Anchor d iameter. For most bonded anchor systems the bond strength measured in short term tests decreases somewhat with increasing anchor diameter according to Eligehausen et al. (2006b). In general, it is assumed that bond strength is independent of the anchor diameter if within the manufacturers recommendations for hole diameter.

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60 Type of c oncrete. The concrete mix design can affect the bond strength of the adhesive anchor. This includes but is not limited to t he type of cement, mix proportions, and the types of additives (air entrainment, plasticizers, fly ash, blast furnace slag). Tests conducted at the University of Florida by Anderson (1999), showed a reduction in bond stress in anchors installed in concret e with fly ash and blast furnace slag as compared to anchors installed in regular concrete without additives. Concrete s trength. According to Cook and Konz (2001) there was no consistent correlation between bond strength and concrete strength among the adhesives tested. As concrete strength was increased, some adhesives showed an increase in bond strength, and others displayed a local maximum or minimum at midrange strengths ( Figure 2 3 ). This reveals that no broad rules can be applied, but must be determined for each adhesive. In the extreme cases, as the concrete strength was increased by 100%, the largest increase in bond strength was 120% and the largest decrease was 35%. According to Eligehausen et al. (2006b ), while increased concrete strength can improve bond strength when the failure is along the side of the hole, this increase can be offset by the increased smoothness that can occur when dril ling in stronger concrete. Bond strength can be reduced in very hi gh strength concrete due to very smooth sided holes. Type of c oarse a ggregate. Cook and Konz (2001) determined through lab testing in concrete specimens with limestone and river gravel that the type of coarse aggregate plays a factor in bond strength.

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61 Based on tests conducted by Caldwell (2001), the mineralogy of the aggregate also affects the bond strength. Of all the samples tested, concretes that used calcium rich aggregates such as limestone failed at the lowest anchor loads. Additionally, concretes that used aggregates with high silicon content failed at relatively higher loads, although the findings were not conclusive. Cook and Jain (2005) conducted tests on adhesive anchors in concrete with different coarse aggregate types. It was observed that adhesive anchors installed in concrete with harder coarse aggregates produced higher bond strengths. It was concluded that the harder aggregates created rougher surfaces when the holes were drilled for the anchor. The rougher surface (as mentioned earlier) provided for more mechanical interlock and thus an increase in the bond stre ngth. Cracked or u ncracked c oncrete. Based on research by Eligehausen and Balough (1995) cracked concrete can have a significant impact on adhesive bond strength. The researchers state that anchors in concrete, or the holes in the concrete created for adhesive anchors, will attract or even induce cracks at the anchor/hole location. Cracks in the concrete at an anchor will then tend to break down the bond between the concrete and the adhesive. Based on the research findings of Eligehausen and Balough (1995) and Fuchs et al. (1995), bond strengths in cracked concrete can vary from 33% to 70% of the bond strength in uncracked concrete. Similarly, Meszaros (1999) estimates from his research that bond strengths in cracked concrete are approximately 50% of t he bond strength on uncracked concrete. See Figure 2 4 for a crack in a typical adhesive anchor application.

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62 Concrete a ge Following casting, concret e can remain damp for several days while it hydrates. ICC ES AC308 requires that anchors be installed in concrete after 21 days of curing. Part of this project will be to determine if adhesive anchors installed in early age concrete will have lower short term bond strengths than those installed in concrete beyond 21 days. If lower in strength, this may be due to a synergistic effect due to the very low concrete strengths and the high moisture content present in early age concrete. Synergistic e ffects The above mentioned factors are typically considered independently, however, their combinations can have amplified effects. According to Messler (2004), the combination of several climatic factors (heat, moisture, temperature cycling, moisture cycling, ultra violet radiation, oxidation) can be particularly severe. Adhesive anchors historically have not been tested for moisture and temperat ure combinations. ASTM D1151 provides a standard for testing adhesives under different temperature and humidity exposures. Test M ethods and M aterial S pecifications Related to A dhesive A nchor S ystems The review of test methods and material specifications related to adhesive anchors included national standards, state DOT standards, and international standards. Other test metho ds are also presented. ASTM E488 Standard Test Methods for Strength of Anchors in Concrete and Masonry Elements ASTM E488 provides the fundamental test procedures to determine the short term seismic, fatigue and shock, tensile and shear strengths of concrete and masonry anchors. These procedures serve as the basic building blocks for anchor testing and

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63 are either adopted in full or slightly modified by governing agencies. In all tests, the anchors are installed and conditioned at standard temperature (73F (23C)) and 50% relative humidity. The various tests methods contained within this test standar d are briefly described below. Static t ests. This standard discusses a series of tension a nd shear tests on five anchors for each variation of anchor size, type, embedment depth and location. The tension test subjects an anchor to a tensile load and the shear test subjects the anchor to a shear load. In both tests the load is applied at a continuous load rate that will produce failure in 21 minute. Load and displacement readings are monitored. The tension test can either have a confined or an unconfined test setup. The confined test setup isolates the failure to the adhesive bond surface in order to determine the bond strength. The unconfined test setup allows for bond failure with a shallow concrete cone or compl ete concrete breakout failure. Seismic t ests. This standard discusses a series of seismic tests on five anchors for each variation of anchor size and type. Procedures are specified for both a seismic tension and shear test. In both tests the load is applied in cycles according to a specified program that simulates a seismic event. Load, displacement, and acceleration readings are monitored. The seismic shear test can either be conducted with a direct loading or an indirect loading procedure. The indirect loading procedure attaches a weight to the structural member via the anchor and shakes the structural member thereby applyi ng a seismic force to the anchor. At the end of the seismic shear tests, a short term shear test is conducted to determine its residual strength.

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64 Fatigue t ests. This standard discusses a series of tension and shear fatigue tests using any of the previous ly demonstrated test setups. In both tests the load is applied according to a fatigue program that specifies the loading method, load levels, frequency, and number of cycles. A short term tension test is conducted at the conclusion of the fatigue loading program to determine the residual strength and failure mode. Shock t ests. This standard discusses a series of tension and shear shock tests to determine either (1) if an anchor system will withstand a certain shock load or (2) the maximum shock load an anchor system can withstand without failure. The shock load is applied in a ramp loading rate over a duration of 30 ms per shock. A short term tension test is conducted at the conclusion of the shock test to determine the residual strength. ASTM E1512 St andard Test Methods for Testing Bond Performance of Bonded Anchors ASTM E1512 builds upon the test program established in ASTM E488 and while ASTM E488 is for all concrete anchor systems, ASTM E1512 is solely for bonded anchors. As with ASTM E488, ASTM E1512 is adopted by many governing agencies for the testing and evaluation of adhesive anchor systems. ASTM E1512 requires that short term, fatigue, and seismic tests be conducted per the procedures set forth in ASTM E488, and specifies additional environmental test procedures. The requirements for the environmental tests are as follows: Concrete of the same mix design in all series with the compressive strength between 2,500 psi and 3,500 psi at the time of testing Concrete cured for 28 days Anchors install ed at 75F 10F (24C 5C) Uses 13 UNC threaded rods embedded 4 in concrete

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65 Either confined or unconfined test, but all test series shall be the same. The following environmental tests are briefly described below. Test on s hort t erm e ffect of f ire. This test evaluates the performance of an anchor in a fire. This is an unconfined test on a minimum of three anchors in concrete. The slab is conditioned and the fire is applied as set forth in ASTM E119. A constant tension load is applied and temperat ure and displacement readings are recorded at one minute intervals until failure. Radiation t est. This test evaluates the radiation resistance of an adhesive anchor system. The anchors are exposed to a minimum gamma radiation level of 2 x 107 rads. Short term tension tests (confined or unconfined) are conducted and the irradiated samples are compared to baseline (confined or unconfined) samples. Tests on e ffect of f reezing and t hawing c onditions. This test evaluates the freeze thaw resistance of an adhesive anchor system. A minimum of three confined or unconfined tests are conducted. Freeze resistant concrete is used and the surface of the concrete is covered with of water for a minimum of 3 around the anchor. A constant tension load is applie d equal to 40% of the ultimate capacity. Fifty complete freeze thaw cycles are conducted by lowering the temperature to 10F ( 23C), holding for three hours then raising to 104F (40C) and holding for three hours. Short term tension tests are conducted following the fifty freezethaw cycles and the residual strength is compared to the baseline strength. Test on e ffects of d amp e nvironment. This test evaluates the sensitivity of an anchor system installed in damp or water filled holes. A minimum of three confined or unconfined tests are conducted. Prior to anchor installation, the holes are filled with tap water and kept full for seven days. The freestanding water is removed immediately

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66 before anchor installation. Following the required curing time, short term tension tests are conducted to failure and the results compared to the baseline test. This test can also be conducted on water filled holes in which the freestanding water is not removed prior to anchor installation. Test on e ffect of e levated t emperature on c ured s amples. This test determines an adhesive anchors sensitivity to elevated temperature under short term loads. A minimum of three confined or unconfined tests are conducted per temperature. Tests are conducted at 70F (21C) and at least four higher temperatures, one of which is at least 180F (82C). The anchors are installed and cured at 75F 10F (24C 5C) and following the cure time the specimens are heated to their test temperature. After stabilizing at 24 hours, the speci mens are removed and short term tension tests are conducted. The short term strengths for each test are normalized by the 70F (21C) test strength and presented in a chart showing the trend of normalized strength versus temperature. See Figure 2 5 for a sample bond strength versus temperature chart for three hypothetical adhesives. Test on e ffect of r educed t emperature on c uring. This test determines an adhesive anchors sensitivity to curing at reduced temperature. A minimum of three confined or unconfined tests are conducted. The test member and anchor rod are conditioned at the test temperature for 24 hours prior to installation. The anchor is then installed and once curing is completed, a short term tension test is conducted and compared to a baseline test at 70F (21C). If the adhesive anchor is to be used below 50F (10C) an additional test is conducted. The conditioning and installation procedure is the same as described

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67 above. However, prior to removal of the specimen from the environmental chamber, a preload of 25% of the ultimate load is applied to the anchor. Once removed from the chamber, the specimen is heated uniformly to 75F 10F (24C 5C) over a period of 72 to 96 hours. Temperature and displacement readings are taken during this heating period. A shor t term tension test is conducted to failure once the specimen has reached the desired temperature. Creep t est. A minimum of three confined or unconfined tests are conducted per creep test series. The creep test is comprised of three separate individual t ests as described below: Static Tension Test Series at 75F 10F (24C 5C) This test series conducts a short term tension test in order to determine the average ultimate tension load. Static Tension Test Series at Elevated Temperature. This test seri es conducts a short term tension test at a minimum concrete temperature of 110F (43C) to determine the average displacement at the ultimate tension load. Creep Test Series at Elevated Temperature. Upon completion of the adhesive curing period, the concrete temperature is raised to a minimum temperature of 110F 3F (43 C 2C) and stabilized for at least 24 hours. Next a preload of no more than 5% of the sustained creep load (40% of the ultimate tension load determined from the short term tension test series at 75F 10F (24C 5C)) is applied to set the anchor and testing equipment before zeroing the test readings. Once the test equipment is zeroed, the remainder of the load is applied. The initial elastic displacement is recorded within the f irst three minutes of the test and subsequent displacement readings are taken every hour for the first six hours, and then daily for the remainder of the test. Concrete temperature readings are conducted during the test and if the concrete temperature fall s below the minimum temperature for more than 24 hours, the test duration is extended to account for the total time below the minimum temperature. The test is continued for 42 days (1000 hours). A logarithmic trendline of the displacement versus time is projected out to 600 days using a least squares fit through the data points using the equation:

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68 where: projected displacement t time a & b constants evaluated by regression analysis This trendline is constructed from not less than the last 20 days (minimum of 20 data points). The projected displacement at 600 days is compared to the displacement from the short term tension test series at elevated temperature See Figure 2 6 for a graphical presentation of this projection. ICCES AC58 Acceptance Criteria for Adhesive Anchors in Concrete and Masonry Elements ICCES AC58 is an acceptance criteria based on allowable stress design (ASD) developed by the International Code Council Evaluation Service (ICC ES) and first approved in January 1995. The purpose of these acceptance criteria was to provide a standard method and report for manufacturers to qualify their adhesi ve anchor products for use in concrete and masonry elements. Beginning in 2008, ICC ES AC58 was no longer accepted by the International Building Code for anchorages in concrete and was replaced by ICC ES AC308 (discussed later) and the current version of ICCES AC58 (2007) only addresses anchorages in masonry elements. A brief discussion of ICC ES AC58 (2005) is presented to provide a historical basis of adhesive anchor testing in concrete. Twenty one test series were identified by ICC ES AC58 and many were based on ASTM E488 and ASTM E1512. There were 15 service condition tests in order to determine design values. Of these 15 service condition tests, 11 were tension tests, three were shear tests, and one was an oblique tension test. There were also six

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69 suitability requirement tests to evaluate the adhesive systems suitability for various conditions. It is important to note that of the 21 tests, only five were mandatory. If the anchor was not tested for the various optional tests, then it could not be qualified for that use. Service c ondition t ests Test series 13 were short term tension tests on single anchors and reference the short term tension test procedure set forth in ASTM E488. These three test series were conducted at three different concrete strengths. Test series 47 evaluated the critical and minimum edge distances for tension loading. The different test series were all for single anchors and varied the concrete strength. Test series 811 evaluated t he critical and minimum spacing for anchor groups of two and four anchors. Test series 12 was the short term shear test of a single anchor and referenced the short term shear test procedure set forth in ASTM E488. Test series 1314 evaluated the cri tical and minimum edge distance for shear loading. Test series 15 was a combined tension and shear short term test in which the direction of loading was at a 45 angle from the concrete. Suitability r equirement t ests Fire r esistance t est (optional). This test referenced the test on short term effec t of fire found in ASTM E1512. The test results were used to determine loads for hourly fire ratings.

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70 Creep t est (optional). ICCES AC58 referred to ASTM E488 and ASTM E1512 for the general creep test procedure, with the following differences: Anchors were installed and cured at 70F 5F (21C 3C) The Static Tension Test Series was conducted at 70F 5F (21C 3C) Provided an allowable temperature tolerance of 3F (1.7C) during the Static Tension Test Series at Elevated Temperature and the Creep Test Series at Elevated Temperature The average displacement at the mean short term load must have satisfied the displacement limitations presented in tables in ICC ES AC58 D ata was projected as discussed in the creep test procedure in ASTM E1512 ( Figure 2 6 ). The anchor was accepted for creep if the average projected displacement at 600 days was less than (a) the average displacement at mean short term load determined from short term tension test ser ies at elevated temperature ( Figure 2 7 ) and (b) 0.12 inches. The rationale behind the acceptance criteria for the creep test procedure for adhesive anchors in ICC ES AC58 is described in detail in NCHRP (2009) but is summarized below. The 110F test temperature was chosen based on a CALTRANS report by Dusel and Mir (1991) It was decided t hat this was an acceptable peak temperature for an anchor installed in a concrete bridge located in the California desert. The sustained load of 40% was based on a conversion from ASD with a factor of safety of 4 and a 1.6 multiplier for maximum anticipat ed sustained load. The test duration was determined from a database of tests in which tests that failed within a 120 testing period did not pullout after 21 days, therefore that duration was doubled to arrive at a 42 day testing period. The 600 day projection was chosen as it was determined that there would be

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71 approximately 600 days (later increased to 10 years) in which an anchor could be expected to be above 110F over a given lifetime of 50 years. In s ervice t emperature t est (required). This test refe renced the test on the effect of service temperature found in ASTM E1512. The results were used to establish adjustment factors for service loads. Dampness t est (optional). This test referenced the test on the effects of damp environment found in ASTM E1512. Control specimens were also tested which had the same properties as the damp specimens except they were maintained dry. The average tension load of the damp specimens must have been at least 80% of the average tension load of the control specimens. Each damp specimen result must not have varied from the average by 15% or all results must have been greater than 80% of the average tension load of the control specimens. Freezing and t hawing t est (optional). This test referenced the test on the effects of freezing and thawing conditions found in ASTM E1512. Seismic t est (optional). ICCES AC58 provided two methods for seismic testing. Seismic Method 1 referred to the SEAOSC (1997) Standard Method for the t est procedure and acceptance criteria. Seismic Method 2 subjected five diameter anchors to a simulated alternating sinusoidal loading cycle in both tension and shear tests. For the seismic tension tests, the maximum tension load ( Ns) was 1.5 times the desired qualified tension load. The anchor was subjected to a series of sinusoidal loads of varying magnitudes and frequencies as listed below: 10 cycles at Ns 30 cycles at Ni = 0.625 Ns

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72 100 cycles at Nm = 0.25 Ns Following the cyclic loading, a short term tension test was conducted to determine residual capacity. The anchor was accepted if it withstood the cyclic loading, the residual capacity was at least 80% of the ultimate short term tension load, and the maximum displacement satisfied ICCES AC58 Equat ion 3 : ult ref s nsT N where: ns maximum displacement during seismic test T ref average ultimate tension load ult displacement limitation for ultimate tension load For the seismic shear tests, the maximum shear load ( Vs) was 1.5 times the desired qualified shear load. The anchor was subjected to a series of sinusoidal loads of varying magnitudes and frequencies as listed below: 10 cycles at Vs 30 cycles at Vi = 0.625 Vs 100 cycles at Vm = 0.25 Vs Following the cyclic loading, a short term shear test was conducted to determine residual capacity. The anchor was accepted if it withstood the cyclic loading, the residual capacity was at least 80% of the ultimate short term shear load, and the maximum displacement satisfied ICCES AC58 Equation 4: ult ref s nsV V 2 where:

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73 ns maximum displacement during seismic test V ref average ultimate shear load ult displacement limitation for ultimate shear load Torque t ests. This test conducted five torque tests per anchor diameter. The manufacturers specified torque moment was applied to the adhesive anchor and the resulting prestressing force was recorded. The 95% fractile of the prestressing force must have been less t han 60% of the 5% fractile of the ultimate load of the confined reference tests. ICCES AC308 Acceptance Criteria for Post Installed Adhesive Anchors in Concrete Elements ICCES AC308 was an acceptance criteria for adhesive anchors in concrete elements bas ed on ultimate strength design (LRFD) developed by the International Code Council Evaluation Service (ICC ES). The purpose of these acceptance criteria was to provide a standard method and report for manufacturers to qualify their post installed adhesive anchor products. Beginning in 2008, ICC ES AC308 replaced the previous acceptance criteria ICC ES AC58 for installations in concrete. ICCES AC308 was the source document for ACI 355.411. Therefore the tests methods and specifications prescribed by ICC ES AC308 are not discussed, rather a focus is on the test procedures and specifications found in ACI 355.4 11. ACI 355.411 Qualification of Post Installed Adhesive Anchors in Concrete ACI 355.411 presents the testing and evaluation program of post installed adhesive anchors in concrete. ICC ES AC308 served as the basis for ACI 355.411 which was published by the American Concrete Institute (ACI) in 2011. Due to the tremendous research and development invested into ICC ES AC308, and the

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74 consensus review process conducted by ACI, it wa s suggested that ACI 355.411 serve as the basis for the testing program and specifications for AASHTO. The testing program specified by ACI 355.411 evaluates the following variables and installation and use conditions: Hole cleaning procedures. Typical manufacturer instructions can include vacuuming, blowing with compressed air, and brushing. Instructions indicate the number of brushes, duration, and cycles and can vary due to moisture condition of the concrete at installation. The default installation condition is dry concrete. Permitted drilling methods. Evaluates installations in holes created with rotary hammer drill with carbide tip, core drill, and rock dril l. The default drilling method is rotary hammer drill with carbide tip. Hole orientation. Tests anchors oriented in the down, horizontal, and overhead orientation. The default orientation is down. Installation temperature. The default installation temperature range of the concrete is 50F to 80F (10C to 27C). Some test procedures allow installation at lower temperatures. Embedment depth and anchor diameter. The embedment depth and anchor diameters tested are specified by the manufacturer and wi thin the ranges established by ACI 355.411. Type of anchor. Tests various materials (carbon, stainless), strengths, and geometries (threaded rod, deformed rebar, internally threaded inserts). Environmental conditions of use. Testing conditions are dry and wet environment with a service temperature range of 32F to 104F (0C to 40C). Optional conditions are elevated temperature and freezingthawing conditions. Chemical exposure. Default condition is a high alkaline wet condition. The optional conditi on is sulfur dioxide. Concrete condition. Either uncracked or both cracked and uncracked. Loading. The default loading conditions are short term and sustained loading. Seismic loading is optional. Member thickness. Determines the minimum thickness of a member to avoid spalling on the backside.

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75 ACI 355.411 has four basic types of tests (Identification Tests, Reference Tests, Reliability Tests, and Service Condition Tests). Additional Supplemental ServiceCondition tests and Assessment tests are also included. The testing schedule is presented in three tables (ACI 355.411 Table 3.1, 3.3) dividing between cracked and uncracked concrete applications. Optional tests are identified in the tables. The reduced testing program mentioned by ACI 355.411 Table 3.3 uses predefined ratios of the characteristic limiting bond stress for use in cracked and in uncracked concrete. The characteristic bond stress is based on the 5% fractile as discussed earlier. For conciseness, the test descriptions in this report are referred to by their ACI 355.411 section number. Assessment a pproach ACI 355.411 10.4.4 addresses the requirements on loaddisplacement behavior. The purpose of the procedure presented is to locate the point on the loaddisplacement curve that repr esents an uncontrolled slip under tension. This point is identified as Nadh, or the loss of adhesion. Loss of adhesion occurs when the anchor and adhesive are extracted from the hole as a unit which is dependent primarily upon the roughness of the hole and is seen as a drastic loss in stiffness on a loaddisplacement curve ( Figure 2 8 ). The ACI 355.411 procedure to locate Nadh is as follows: Determine a tangent stiffness at 30% of the peak short term load ( Nu) which is typically approximated as the secant stiffness from the origin to the point on the loaddisplacement curve at 0.30Nu. ntil it intersects with the loaddisplacement curve Nadh is taken at the point of a sudden change in stiffness ( Figure 2 8 )

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76 If there is not a very sud the loaddisplacement curve before the peak, Nadh is taken at the intersection ( Figure 2 9 ). the loaddisplacement curve after the peak, Nadh is taken at the peak ( Figure 2 10). If the displacement at 0.30Nu is less than 0.002, the origin is shifted to the point on the loaddisplacement curve at 0.30Nu and Nadh is taken at the intersection of displacement curve ( Figure 2 11) Most of the tests discussed (except for the identification tests and test series: ACI 355.411 .0, .7, 7.8, .13, .19, .8, .9, .10, .11, 8.13, 9.1, .2) have a requirement on the coefficient of variation for load and displacement which is addressed in ACI 355.411 10.4.2 and establishes a reduction factor if the coefficient of variation from the tests exceed a certain threshold (30% for ultimate loads in reliability tests and 20% for other tests.) Identification t ests In order to positively identify the adhesive being tested and compare it against the manufacturers standard; ACI 355.411 .3 requires that at least three of the following tests be conducted. Infrared absorption spectroscopy per ASTM E1252 Bond strength per ASTM C882 or equivalent Specific gravity per ASTM D1875 Gel time per ASTM C881 Viscosity per ASTM D2556, ASTM F1080, or equivalent Other appropriate tests to positively identify the material Reference t ests For each batch of concrete, reference short term tests are performed to establish baseline values to later calculate a ratio specific test results to the reference test results for the subsequent reliability and servicecondition tests. These tests follow the ASTM E488 short term test procedure and are conducted in dry

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77 concrete at standard temperature. These tests are referred to as 1a to 1d in ACI 355.411 Tables 3.1 3.3. Reliability t ests Reliability tests are conducted to determine an adhesive anchors performance under adverse installation conditions and sustained load. In the listing of the tests below, the ACI 355.411 section number is included for reference. The baseline strength determined in the reference tests are used to evaluate the 355.411 Eq uation 10 7 which is compared to a limit referred to as req. = ; where: mean bond stress from reliability test series in concrete batch or test member i mean bond stress from reference test series in concrete batch or test member i characteristic bond stress from reliability test series in concrete batch or test member i calculated in accordance with ACI 355.411 .3 characteristic bond stress from reference test series in concrete batch or test member i calculated in accordance with ACI 355.411 .3 controlling value for reliability tests and service condition tests where calculation of is required The reference value ( req) is specific to each test and is either given in Tables 3.1 3.3 or determined from ACI 355.411 10.4.6 based on the anchor category.

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78 Sensitivity to h ole c leaning, d ry c oncrete (ACI 355.411 .5). This test evaluates the sensitivity of an adhesive anc hor to the degree of hole cleaning prior to installation in dry concrete. The hole is cleaned with 50% of the manufacturers cleaning instructions. If the manufacturer does not specify the cleaning operation, no cleaning is conducted. A short term tensi on test is conducted as specified in ASTM E488 continuously monitoring load and displacement to determine the ratio per ACI 355.411 Eq uation 10 7. This test is not required if the manufacturer requires that the holes be flushed with water. Sensitivity to h ole c leaning, s aturated c oncrete (ACI 355.411 7.6). This test evaluates the sensitivity of an adhesive anchor to the degree of hole cleaning prior to installation in saturated concrete. A pilot hole about half the diameter of the intended hole is drilled and kept filled with water for eight days or until the concrete is saturated over a diameter of 1.5 times the hole diameter. Prior to installation, the water is removed with a vacuum and the hole is drilled to the required diameter. The hole is cleaned with the 50% cleaning effort as mentioned in ACI 355.411 .5 and the anchor is installed. Flushing the hole with water is allowed if specified by the manufacturer. A short term tension test is conducted as specified in ASTM E488 conti nuously monitoring load and displacement to determi ne the ratio per ACI 355.411 Equation 107. Sensitivity to h ole c leaning, w ater f illed h ole (ACI 355.411 7.7, optional). This test evaluates the sensitivity of an adhesive anchor to the degree of hol e cleaning prior to installation in a water filled hole. The test is identical to the test described in ACI 355.411 .6, except that the hole is filled with water after the reduced cleaning procedure. A short term tension test is conducted as specified in ASTM E488

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79 continuously monitoring load and displacement to determine the ratio per ACI 355.411 Eq uation 107. Sensitivity to h ole c leaning, s ubmerged c oncrete (ACI 355.411 7.8, optional). This test evaluates the sensitivity of an adhesive anchor to the degree of hole cleaning prior to installation in submerged concrete. The concrete member is covered with at least of water during drilling, the reduced cleaning effort (as described in ACI 355.4 11 .5), installation, and testing. A short term tension test is conducted as specified in ASTM E488 continuously monitoring load and displacement to determine the ratio per ACI 355.411 Eq uation 107. Sensitivity to m ixing e ffort (ACI 355.411 .9 ). This test evaluates the sensitivity of the adhesi ve to a reduced mixing effort. This test is only for adhesive anchor systems in which the mixing of the adhesive components is controlled by the installer such as systems that require mixing until a color change occurs, or mixing for a specific duration or number of mixing repetitions. This test is not required for systems that use a cartridge system with static mixing nozzles or capsule anchor systems. A reduced mixing effort is defined as mixing the adhesive for only 75% of the required mixing time spe cified by the manufacturer. A short term tension test is conducted as specified in ASTM E488 continuously monitoring load and displacement to determine the ratio per ACI 355.411 Eq uation 107. Sensitivity to i nstallation in w ater s aturated c oncrete (AC I 355.4 11 7.10, optional). This test evaluates the sensitivity of an adhesive anchor to installation in saturated concrete. This test is similar to the test specified in ACI 355.411 7.6 except that it requires a full cleaning effort as prescribed by the manufacturer. A short term

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80 tension test is conducted as specified in ASTM E488 continuously monitoring load and displacement to determi ne the ratio per ACI 355.411 Equation 107. Sensitivity to i nstallation in a w ater f illed h ole, s aturated c oncret e (ACI 355.411 .11). This test evaluates the sensitivity of an adhesive anchor installation in a water filled hole. This test is similar to the test specified in ACI 355.411 .7 except that it requires a full cleaning effort as prescribed by the manufacturer. A short term tension test is conducted as specified in ASTM E488 continuously monitoring load and displacement to determine the ratio per ACI 355.411 Eq uation 107. Sensitivity to i nstallation in s ubmerged c oncrete (ACI 355.411 .12, optional). This test evaluates the sensitivity of an adhesive anchor installation in submerged concrete. This test is similar to the test specified in ACI 355.411 .8 except that it requires a full cleaning effort as prescribed by the manufacturer. A short term tension test is conducted as specified in ASTM E488 continuously monitoring load and displacement to determine the ratio per ACI 355.411 Eq uation 107. Sensitivity to c rack w idth, l ow s trength c oncrete (ACI 355.411 .13). This test evaluat es the sensitivity of an adhesive anchor installed in low strength concrete with a wide crack passing through the anchor location. Following anchor installation and adhesive curing, the crack is widened and a short term tension test as specified in ASTM E 488 is conducted continuously monitoring load, displacement, and crack width to determine the ratio per ACI 355.411 Eq uation 107. Sensitivity to c rack w idth, h ighs trength c oncrete (ACI 355.411 .14). This test is similar to the test specified in AC I 355.411 7.13 except that the concrete specimen is of highstrength concrete.

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81 Sensitivity to c rack w idth c ycling (ACI 355.411 .15). This test evaluates an adhesive anchors performance in cracked concrete whose crack width is cycled. An anchor is installed so that a crack runs through the middle of the hole and a tension load of about 30% of its characteristic resistance is applied. While the load is maintained on the anchor, the test member is cyclically loaded so that the crack width is cycled between two set limits at a frequency of 0.2 Hz for 1000 cycles. Load and displacement are measured during the test and following the 1000 cycles the anchor is unloaded and the resulting displacement and crack width is measured. A short term tension test as specified in ASTM E488 is conducted continuously monitoring load and displacement to determine the ratio per ACI 355.411 Eq uation 10 7. Additionally, the cumulative anchor displacement after 20 cycles must be less than 0.080 and the cumulative anchor displacement after the 1000 cycles must be less than 0.120. Sensitivity to f reezing and t hawing (ACI 355.411 .16). This test deter mines the performance of an adhesive anchor under freezing and thawing conditions. An anchor is installed in concrete and the top surface of the concrete is covered with of water for a distance of 3 around the anchor. The anchor is loaded with a sust ained load of about 55% of the average ultimate tension load of reference tests. Within two hours the temperature is lowered to 4F 5F ( 20C 2C) and maintained for 14 hours, the temperature is then raised to +68F 5F (+20C 2C) within one h our and maintained for 14 hours. Fifty such cycles are conducted measuring load, displacement, and temperature. Following the fifty cycles a short term tension test as specified in ASTM E488 is conducted continuously monitoring load and displacement to d etermine the ratio per ACI 355.411 Eq uation 10 7. Additionally, the rate of

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82 displacement increase shall decrease to zero as the number of freezethaw cycles increase. Sensitivity to s ustained l oading at s tandard and m aximum l ong t erm t emperature (ACI 3 55.4 11 .17). The sustained loading test is similar to the procedure from ICC ES AC58 (based on ASTM E1512) with the following changes: The sustained load is increased to about 55% of the average tension capacity of the reference tests. Sustained load t ests are conducted at both standard temperature and the long term elevated temperature. Following the 42 day (1000 hr) sustained load tests, the anchors are loaded until failure to determine the residual capacity The acceptance criteria as presented in IC C ES AC58 w ere modified in the development of ICC ES AC308 and are reflected in ACI 355.411. The displacement data is projected from the last 20 days (minimum of 20 data points) from the creep test using the Findley power law (instead of the logarithmic model) shown in ACI 355.411 Eq uation 1024. ( ) = + where: ( ) total displacement at time t initial displacement under sustained load t time corresponding to the recorded displacement a, b constants evaluated from a regression analysis Using A CI 355.411 Equation 1024, the displacement is then estimated at the service lives of ten years and 50 years. The adhesive anchor is accepted for sustained load if: The projected displacement at ten years is less than the mean displacement at loss of adhesion for the reference test at elevated temperature

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83 The projected displacement at 50 years is less than the mean displacement at loss of adhesion for the reference test at standard temperature. The residual capacity is greater than 90% of the reference tests capacity Sensitivity to i nstallation d irection (ACI 355.411 7.18, optional). This test evaluates the sensitivity of an adhesive anchor to hole orientation (horizontal or upward). This test installs anchors in holes that are oriented horizontally and vertically overhead. The anchors are installed with the most unfavorable installation temperature of the concrete and the adhesive. Short term tension tests are conducted as specified in ASTM E488 continuously monitoring load and displacement to determine the ratio per ACI 355.411 Eq uation 10 7. Additionally, the anchor must not displace more than 0.05 times the anchor diameter during curing. There are additional subjective assessments on the adequacy of the manufacturers procedures for overhead and horizontal installations. The effectiveness of the overhead installation procedure can be verified by the procedure shown in Figure 2 12 Torque t ests (ACI 355.411 .19). This test evaluates the maximum torque that can be applied to an adhesive anchor without damaging the adhesive bond or yielding the anchor. Torque is applied t o the anchor and measurements of torque and the resulting induced tension in the anchor are recorded. The torque reached in the test must be greater than 130% of the tightening torque specified by the manufacturer. Servicec ondition t ests These tests are conducted to determine an adhesive anchors performance under service conditions. In the listing of the tests below, the ACI 355.411 section number is included for reference.

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84 Tension t ests in u ncracked and c racked c oncrete (ACI 355.411 .4). These tests are conducted to determine the adhesive anchors unconfined tension strength per ASTM E488 and are used as a baseline for unconfined tests. Tests are conducted in both low and high strength concrete for cracked and uncracked conditions. Tens ion t ests at e levated t emperature (ACI 355.411 8.5). These tests are conducted to determine an adhesive anchors sensitivity to elevated temperature. Short term tension tests are conducted at various temperatures per Table 8.1 in ACI 355.411 (shown as Table 2 1 ). Anchors are installed and cured at standard temperature for both categories. For category A, tests are conducted at the long term and t he short term temperature. For category B, tests are conducted at standard temperature, at the long term temperature, at the short term temperature, and at least two temperatures between the long term and the short term temperature with a maximum incremen t of 35F (20C). Following the cure time, the anchors are heated to the test temperature and tested per ASTM E488 with continuous measurements of load and displacement. Tests must be completed before the test member temperature falls below the test temperature. The ratios lt and st are calculated from the sustained load and short term tests respectively as shown in ACI 355.411 Equations 10 26 and 1027 below. = ; 1 0 = 0 8 ; 0 8 1 0 where: mean tension capacity at long term elevated temperature mean tension capacity at short term elevated temperature

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85 mean tension capacity of an anchor in reference test series i characteristic tension capacity at long term elevated temperature characteristic tension capacity at short term elevated temperature characteristic tension capacity of an anchor in reference test series i Tension t ests with d ecreased i nstallation t emperature (ACI 355.411 .6, optional). These tests determine an adhesive anchors sensitivity to installation at reduced temperature. A minimum of five confined tests in uncracked concrete are conducted. The test member and anchor rod are conditioned at a test temperature below 50F (10C) for 24 hours prior to installation. The anchor is then installed and cured at the desired temperature. Once curing is completed, a short term tension test is conducted. If the test temperature is below 40F (5C) an additional test is conducted. The conditioning and installation procedure is the same as described above. However, prior to removal of the specimen from the environmental chamber, a preload of about 55% of the ultimate load is applied to the anchor. The specimen is then removed from the chamber and is heated uniformly to standard temperature over a period of 72 to 96 hours. Temperature and displacement readings are taken during this heating period. Once the specimen has reached the desired temperat ure, a short term tension test is conducted to failure. The mean and the 5% fractile of these tests shall be statistically equivalent to those of the reference tests. ACI 355.411 define s statistically equivalent if there are

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86 no significant differences between the means and between the standard deviations of the two groups. Such statistical equivalence shall be demonstrated using a onesided Students t Test at a confidence level of 90%. Additionally, for anchors installed in concrete below 50F (10C) the displacement of the anchor under the sustained preload portion shall stabilize prior to short term tension testing. Establishment of c ure t ime at s tandard t emperature (ACI 355.4 11 .7). These tests are conducted to determine an adhesive anchors sensitivity to reduced cure time. Comparison tests are conducted on anchors allowed to cure for the minimum curing time and on anchors that were cured for 24 hours longer than the minimum curing time. Confined short term tension tests are conducted in uncracked concrete as specified in ASTM E488 while continuously monitoring load and displacement. The acceptance criterion for these tests is shown as ACI 355.411 Eq uation 1028: ; 0 9 where: mean tension capacity corresponding to the manufacturers published minimum cure time mean tension capacity corresponding to the manufacturers published minimum cure time + 24 hours characteristic tension capacity corresponding to the manufacturers published minimum cure time characteristic tension capacity corresponding to the manufacturers published minimum cure time + 24 hours

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87 Durability a ssessment (ACI 355.411 8.8, sulfur test is optional ). These tests determine an adhesive anchors sensitivity to harsh environments. Mandatory alkalinity tests are conducted and optional sulfur dioxide tests can be conducted. Specimens are made by installing adhesive anchors in 6 diameter concrete cylinders cast in PVC or steel pipe. After installation and curing, the cylinders are sliced into 13/16 1/8 thick slices. A minimum of ten slices are to be made for each environmental condition tested plus ten for reference tests. The reference slices ar e stored at standard temperature and 50% relative humidity for 2000 hours. The slices for the high alkalinity environment tests are stored for 2000 hours in an alkaline solution with a pH = 13.2. The slices for the optional sulfur dioxide tests are tested according to EN ISO 6988 (Kesternich Test) with a concentration of 0.67% for at least 80 cycles. Following storage, the anchors are punched out of the slices with the concrete restrained in a device similar to that shown in Figure 2 13. The bond stress for each slice is the peak load divided by the circumferential area of the anchor. A reduction factor dur is calculated for each durability test. Ver ification of f ull c oncrete c apacity in a c orner (ACI 355.411 8.9). These tests determine the critical edge distance ( cac) in test members with the minimum thickness as specified by the manufacturer. S hort term tension tests per ASTM E488 are performed in low strength uncracked concrete on anchors located in a corner with equal edge distances of cac. The tension capacity from these tests should be statistically equivalent to the tension capacity of reference tests performed away from a corner.

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88 Determination of m inimum s pacing and e dge d istance to p reclude s plitting (ACI 355.411 8.10, optional). The purpose of these tests is to evaluate the shear capacity of adhesive anchors. S hort term shear tests away from edges are performed per ASTM E488. The concrete should not crack during the test and the mean failure load must be greater than 90% of the expected failure load. Test to d etermine s hear c apacity of a nchor e lements with n onu niform c ross s ection (ACI 355.411 .11). The purpose of these tests is to determine the shear capacity of anchors in which the shear capacity cannot be reliability calculated due to a nonuniform cross section. S hort term shear tests away from edges are performed per ASTM E488 with a few requirements on edge spacing and embedment depth. Simulated s eismic t ension t ests (ACI 355.411 8.12, optional). The purpose of these tests is to evaluate adhesive anchors subjected to a simulated seismic tension load in cracked concrete. Anc hors are installed in a crack which is opened by 0.020 prior to loading. A sinusoidal tension load is applied to the anchor with a frequency between 0.1 and 2 Hz. The peak tension load is initially at Neq for 10 cycles, then reduced to Ni for 30 cycles and finally to Nm for 100 cycles, where: Neq = about 50% of the mean tension capacity of reference tests Ni = 75% Neq Nm = 50% Neq During the test, crack width, tension load, and displacement are recorded. Following the seismic loading, the crack is opened to the maximum crack width during the seismic test and a short term tension test is conducted in accordance with ASTM E488 until failure.

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89 For acceptance, the anchors must complete the seismic loading cycle without failure. Upon completion, the residual strength of the anchor must be at least 160% of Neq. If the anchor does not complete the seismic loading cycle, a reduced value for Neq ( Neq,reduced) is used until the anchors pass the criteria. If a reduced loading cycle is performed a r eduction factor N,seis is determined by dividing Neq,reduced by Neq. Simulated s eismic s hear t ests (ACI 355.411 8.13, optional). The purpose of these tests is to evaluate adhesive anchors subjected to a simulated seismic shear load in cracked concrete. Anchors are installed in a crack which is opened by 0.020 prior to loading. A sinusoidal shear load is applied to the anchor parallel to the crack with a frequency between 0.1 and 2 Hz. The peak shear load is initially at Veq for 10 cycles, then reduc ed to Vi for 30 cycles and finally to Vm for 100 cycles, where: Veq = about 50% of the mean shear capacity of reference tests Vi = 75% Veq Vm = 50% Veq During the test, crack width, shear load, and displacement are recorded. Following the seismic loading, the crack is opened to the maximum crack width during the seismic test and a short term shear test is conducted in accordance with ASTM E488 until fail ure. For acceptance, the anchors must complete the seismic loading cycle without failure. Upon completion, the residual strength of the anchor must be at least 160% of Veq. If the anchor does not complete the seismic loading cycle, a reduced value for Ve q ( Veq,reduced) is used until the anchors pass the criteria. If a reduced loading cycle is performed a reduction factor V,seis is determined by dividing Veq,reduced by Veq. Additional s upplemental t ests ACI 355.411 specifies a few additional supplemental tests:

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90 Round r obin t ests (ACI 355.411 9.1). These tests examine the effects of regional variations of concrete on the behavior of adhesive anchor systems. Tests are conducted at laboratories located in each time zone of the United States using aggregates representative of that region. Five confined and five unconfined short term tension tests per ASTM E488 are conducted and compared with the original laboratory results to generate an adjustment factor conc for each laboratory and the minimum value i s used. Tests to d etermine m inimum m ember t hickness (ACI 355.411 9.2). These tests verify the minimum member thickness as specified by the manufacturer. Ten anchors are installed at the maximum embedment depth in a concrete member and the member is checked for cracking or spalling. Additional a ssessment t ests A few additio nal assessment tests are included if pertinent. Multiple a nchor t ype s upplementary t ests (ACI 355.411 3.4). These tests investigate the effects of using anchors of different metal composition within an anchor group. The entire test program is conducted with one anchor type, and the other anchor types are subjected to a series of additional tests specified in ACI 355.411 Table 3.4 Alternate d rilling m ethods s upplementary t ests (ACI 355.411 3.5). If the manufacturer permits drilling methods other than with rotary hammer drill and carbide bit supplementary tests are conducted using the alternate drilling method. ACI 355.411 Table 3.5 lists the tests to conduct on the alternate drilling method. If the results of these tests are not statistically equiv alent to the results from their respective tests using the rotary hammer and carbide bit drilling method, all tests need

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91 to be conducted except for the following shear capacity tests for an element having a nonuniform cross section ( ACI 355.411 .11). R esulting d esign v alues The previously described testing program provides design values to be used by ACI 318 11 Appendix D. The bond stress for each servicecondition test ( i) is calculated from ACI 355.411 Equation 10 11: = where: setup 1.0 for unconfined test 0.75 for confined test 0.70 for confined test in cracked concrete N u,i,fc peak tension load in test series i normalized to concrete strength of cf = 2500 psi, lbs d anchor diameter, in h ef embedment depth, in The nominal characteristic bond stress for each servicecondition test ( k,nom(cr,uncr)) is calculated as per Equation 13 shown earlier. The limiting characteristic bond stress for each servicecondition test ( k(cr,uncr)) is adjusted for many reduction factors as shown in ACI 355.411 Equation10 12: ( ) = ( ) where: min ; the reliability and service condition tests listed in ACI 355.411 Table 10.2 and Table 10.3. ratio of reliability test result to reference test result evaluated for all reliability tests listed in ACI 355.411

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92 Table 10.2 adh reduction factor for loss of adhesion as evaluated for all reliability tests listed in ACI 355.411 Table 10.2 and for all service condition tests listed in ACI 355.411 Table 10.3 req threshold value of given in ACI 355.4 11 Table 3.1, Table 3.2 or Table 3.3. lt reduction factor for maximum long term temperature st reduction factor for maximum short term temperature dur reduction factor for durability p min. reduction factor for reduced sustained load in reliability tests conc adjustment factor for regional concrete variation COV reduction factor associated with the coefficient of variation of ultimate loads cat3 reduction factor for anchor category 3 Anchor c ategories Based on the alpha reduction factor results of the reliability tests, anchors are classified into categories depending on the required level of inspection. ACI 355.411 Tables 10.5 and 10.6 are used to compare the alpha reduction factors from the different reliability tests against certain threshold values in order to assign a strength reduction (resistance) factor for design. AASHTO Standard Specifications for Transportation Materials and Methods of Sampling and Testing AASHTO (2008) was reviewed for a framework of specifications within which to incorporate specifications for adhesive anchors. The only test method dealing with adhesive systems was AASHTO (2007b ) T 333 07 which measures the change in length of a cured adh esive material. AASHTO (2010c) TP 84 10 was recently created

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93 to evaluate adhesive anchors using the stress versus timeto failure approach discussed in detail later in the chapter. AASHTO (2007a) M 235M/M 235 03 is the AASHTO version of ASTM C881 which pr ovides specifications for seven types of adhesives and subsequent tests which refer to many ASTM tests. While Type IV are adhesives are for bonding hardened concrete to other materials in loadbearing applications, it is not specifically for epoxy adhesiv e anchor systems. CALTRANS CTM681 Method for Testing Creep Performance of Concrete Anchorage Systems CALTRANS (2001) CTM 681 is a test method to determine the creep performance of cartridge epoxy or resin capsule adhesive systems for bonding rebar dowels or threaded rods into concrete. The procedure is essentially the same creep testing procedure specified in ASTM E1512 with a few modifications as described below: Only mentions an unconfined test setup The testing temperature for the creep test is 112F 2F (44.5C 1C) The sustained load (per Table 2 2 ) must be maintained to within 5% of the required value during the duration of the test Report the mean creep value at 48 hours CALTRANS Standard Specifications CALTRANS (2006b) 75 Miscellaneous Metal lists the requirements for resin capsule anchors tested under CALTRANS (2001) CTM681. A resin capsule anchor must withstand a sustained tensile load for at least 48 hours with a displacement less than 0.035. The applied sustained load shall be in accordance with Table 2 2 Anchors must be made of steel or stainless steel and hot d ip or mechanically galvanized.

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94 CALTRANS has a test method for creep performance of adhesive anchor systems, but no comprehensive material specifications for adhesive anchors could be found in their Standard Specifications. While CALTRANS (2006b) 5 deals with Epoxy, there is no specific mention of an epoxy used for adhesive anchor applications. However, in Section 83 (Buildings and Barriers), there is a comment that anchor bolts that are set with epoxy shall use a 2component epoxy mixture as specified i n Section 952.01 Binder (Adhesive), Epoxy Resin Base. TxDOT DMS 6100 Epoxies and Adhesives TxDOT (2007a) DMS 6100 classif ies epoxies and adhesives into nine types and specifies Type III to be used for dowel and tie bar adhesives. Type III adhesives are further classified into three classes (A C). Class A is a bulk material for horizontal applications, Class B is for vertical applications, and Class C is either a bulk material or cartridge dispensed material for machine application and can be applied horizontally or vertically. Table 2 3 specifies the performance requirements for Type III adhesives tested according to TxDOT (2007b) Tex 614J. TxDOT (2007b) Tex 614J requires that each component be distinctly colored and resul t in a third color when thoroughly mixed. Also the filler in the components must not damage the dispensing equipment and the extruder must meter the proportioning and mixing of the components and handle the viscosity range of the components. TxDOT Tex 6 14J Testing Epoxy Materials TxDOT (2007b) Tex 6 14J is a collection of many material tests for adhesives. Five are required for Type III adhesives. Material specifications are covered in TxDOT (2007a) DMS 6100 dis cussed earlier

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95 Gel Time. This test measures the gel time by mixing a sample at 77F 2F (25C 1C) and probing it with a toothpick until a ball of cured material forms at the center. Viscosity. This test measures the viscosity of the adhesive using a Brookfield viscometer at 77F 2F (25C 1C). Tensile b ond. This test measures the bond strength of an adhesive between two mortar briquettes. Two sets of three specimens are prepared for Type III adhesive. For each specimen, two mortar briquettes are joined with adhesive. One set of specimens is cured for six hours at 77F 2F (25C 1C) and the second set is cured for 48 hours at 120F 2F (49C 1C). Once cured, the specimens are placed into a tensile machine and loaded in tension until failure. Thixotropy b ond @ 120F (49C). This t est forms a 2 by 4 by 0.05 thick sample of adhesive on a metal plate conditioned at 120F 2F (49C 1C). The plates are then placed in an oven at 120F 2F (49C 1C) until the adhesive has hardened. The thickness retained is measured and the thi xotropy bond is calculated as the average of eight thickness readings. Wet p ullout s trength. ksi rebar is installed in a 5/8 diameter by 3.5 deep hole in a 6 diameter by 8 long concrete cylinder. The adhesive and anch or are installed and cured at 77F 3F (25C 1C). Following a 24 hour curing time, the block is submerged upright in a 77F 3F (25C 1C) water bath for six days. The anchor is then loaded in tension until failure. NYSDOT Standard Specifications NYSDOT (2008b) 701 07 Anchoring Materials Chemically Curing specifies the testing and material requirements for polymer anchoring materials for anchor bolts in concrete. The material must be nonmetallic, nonshrink polymer resin in

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96 prepackaged or pr emeasured containers. It cannot contain corrosion promoting agents and must be insensitive to moisture. The material must last at least six months when stored between 40F and 90F. The container must include the mixing instructions, setting time, and expiration date. Section 70107 specifies certain chemical resistances as tested per ASTM D471 at 70F (21C) for 24 hours as noted in Table 2 4 Two series of tension pullout tests are specified for acceptance by the state. Test series 1 conducts three tests using 1 diameter threaded rods embedded 10 in concrete. The pullout load must be greater than the values found in Table 2 5 Test in concrete. The pull out load for each set must be greater than the values found in Table 2 5 NYSDOT (2008c) 654 3.03 Anchorages permits drilling by rotary impact drills only, and specifically does not permit core drills. NYSDOT Engineering Instruction EI 08 012 NYSDOT (2008b) EI 08012 was published in March of 2008 to limit the use of NYSDOT (2008c) 701 07 Anchoring Materials Chemical Curing. This was due to recommendations from the National Transportation Safety Board (NTSB) to limit the use of adhesive anchors in overhead installations or in situations which could pose a risk to public safety. In such situations, NYSDOT recommends using alternative anchoring systems such as cementitious grout or mechanical anchor systems.

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97 FDOT FM 5 568 Florida Method of Test for Anchor Systems for Adhesive Bonded Anchors and Dowels. FDOT (2000) FM 5 568 is a test method for anchor systems with adhesive bonded anchors and dowels. Its purpose i s to determine the bond strength and performance characteristics of adhesive anchors in uncracked concrete. The material specifications for this test method are contained in FDOT (2007) 937 The tests contained in FDOT (2000) reference the test procedur es specified in ASTM E488 and ASTM E1512 with a few modifications/specifications as explained below. Confined t ension. This test method specifies a confined test setup, an anchor Damp Hole i nstallation. This test method specifies a confined test setup, an Elevated t emperature. This test method specifies a confined test setup, an (102 mm), and a minimum temperature of 108F (42C). Horizontal o rientation This test is a short term tension test on an anchor installed and cured in a horizontal orientation. This test method specifies a confined (16 mm), and an embedment of 4 (102 mm). Short t erm c ure. This test is a short term tension test on an anchor installed and cured in a horizontal orientation. This test method specifies a confined test setup, an edment of 4 (102 mm). The test load must be applied within 24 hours after installation. Longt erm l oad ( c reep). This test conducts the creep test series listed in ASTM E1512 with the following specifications:

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98 References ASTM E488 Table 2 for requirement s on the distance between the reaction force and the anchor The minimum sustained tension load of 40% of the average tension failure load is established by an unconfined tension test The minimum testing temperature of the concrete and anchor specimens is 110F (43C). A load duration of 42 days Following the 42 day loading period, the temperature of the specimens are cooled to 70F 5F (21C 3C) and an unconfined tension test is performed Unconfined s tatic t ension t est This test method specifies unconf ined test setups with anchor diameters and embedment depths as follows: An anchor diameter of (19 mm) and embedment of 6 (152 mm ) FDOT Standard Specifications for Road and Bridge Construction The material specifications for adhesive anchor systems for FDOT are found in FDOT (2007) 937 Adhesive Bonding Material Systems for Structural Applications. Only systems that are specifically intended for bonding anchors and dowels into concrete in structural applications are allowed. FDOT restricts the use of adhesives that are manually combined from bulk supplies and only allows systems that are prepackaged in which the two com ponents are in separate chambers and are automatically proportioned and mixed when discharged. Only undamaged full packages can be used (i.e., packages that were previously opened cannot be used). Adhesive anchors can only be installed in positions rangi ng from horizontal to vertically downward. Two types of adhesive systems (HV and HSHV) are defined as follows: Type HV Adhesives: Used in bonding materials for all horizontal installations and vertical installations other than constructing doweled pile splices, except when

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99 Type HSHV is required. Type HV adhesives may not be substituted for Type HSHV adhesives. Type HSHV Adhesives: Use higher strength Type HSHV adhesive bonding materials for installation of traffic railing barrier reinforcement and anchor bolts into existing concrete bridge decks and HV and HSHV systems must be packaged to be automatically proportioned during installation. Section 937 also specifies the minimum performance requirements for tests conducted under F DOT (2000) F M 5 568 as indic ated in Table 2 6 The coefficient of variation of the uniform bond stress is limited to 20%. Three criteria are specified for the Creep Test and are listed as follows: The displacement rate shall decrease during the 42 day test period. The total displacement at 42 days (with load still applied) shall be less than 0.03 and the total displacement due to creep during the last 14 days must be less than 0.003. After the 42 day test, the uniform bond stress from the confined tension test shall not be less than 1800 psi. Finally, a Qualified Products List (QPL) is maintained by FDOT in which manufacturers can apply for their products to be included once they have met the requirements of Section 937. IDOT Laboratory Test Procedure for Chemical Adhesives IDOT (2007a) tests chemical adhesives for dowels and tie bars. The test procedure is for both gun grade adhesives and glass capsule adhesive systems. The glass capsule systems are installed using threaded rods in a diameter hole and embedded 5 into 4000 psi dry concrete at 73F 4F (23C 2C). The gun grade adhesive systems use #5 epoxy coated 60 ksi rebar. The following tests are conducted:

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100 Dry c onditioning. A short term tension test per ASTM E488 is conduc ted within one hour of installation and stopped when the load reaches 16 kips or the displacement reaches 0.1. The anchor system is accepted if it withstood a minimum load of 13.55 kips with less than 0.1 displacement. Wet c onditioning. This test is si milar to the Dry Conditioning test except the hole is filled with water for 12 hours and then removed prior to installation. A short term tension test per ASTM E488 is conducted within one hour of installation and stopped when the load reaches 16 kips or the displacement reaches 0.1. The anchor system is accepted if it withstood a minimum load of 13.55 kips with less than 0.1 displacement. Cold t emperature c onditioning. This test is similar to the Dry Conditioning test except that the adhesive and threaded rod are conditioned to 32F 4F (0C 2C) prior to installation. The anchor is cured for 24 hours at the above temperature. A short term tension test per ASTM E488 is conducted at the end of the 24 hour curing period and loaded until failure. The anchor system is accepted if the displacement at failure was less than 0.1. Compressive s trength. This test is not for glass capsule systems. This tests two 1 diameter by 2 cylinder specimens at 73F 4F (23C 2C). One specimen is tested at one hour and the other at 24 hours after casting. The adhesive is accepted if the one hour compressive strength is greater than 3000 psi and the 24 hour compressive strength is greater than 4000 psi. Horizontal i nstallation s tability. This test is not for glass capsule systems. This test installs a 1 diameter by 14 long smooth steel dowel bar into a horizontal 9 long

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101 accepted if the anchor could be installed by hand wit hout appreciable drain down from the top of the tube. Infrared s pectrophotometer f ingerprint. A fingerprint record is made of the cured adhesive for future reference. IDOT Standard Specifications for Road and Bridge Construction IDOT (2007b) 1027.01 Chemical Adhesive references IDOT (2007a) for the testing and acceptance of chemical adhesives. IDOT (2007b) 1027.01 states that the adhesive must consist of a two part fast setting resin and filler/hardener. WSDOT Standard Specifications WSDOT (2008b) 26 Epoxy Resins lists the various types of epoxy bonding agents per the classification found in ASTM C881. WSDOT (2008b) 6 02.3(18) Placing Anchor Bolts discusses the requirements for placing grouted anchor bolts and does not specifically mention adhesive anchors. MDOT Material Source Guide Specification 712.03J Adhesive Systems for Structural Anchor & Lane Ties of the Qual ified Products List (QPL) in MDOT (2009) states that anchors should be installed per the manufacturers instructions with a minimum embedment depth of 9 diameters for threaded rod. VDOT Road and Bridge Specifications VDOT (2007) 14 Epoxy Resin Systems lists various types of epoxy resin systems for various uses, but does not include adhesive anchors. VDOT (2007) 519 Sound Barrier Walls specifically prohibits the use of epoxy or adhesive anchors

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102 EOTA ETAG 001 Part 5 Bonded Anchors EOTA (2002) ETAG 001 Part 5 addresses bonded anchors. This technical approval document was created in 2002 and has undergone several amendments. EOTA (2002) served as the basis for ICC ES AC308 which subsequently served as the basis for ACI 355.411 discussed above. A review of EOTA (2002) did not provide any new information than what was already discussed with ACI 355.411. fib Design of Anchorages in Concrete The Federation Internationale du Beton (fib) (2011) does not provide adhesive anchor qualification and quality control requirements, rather s ection 1.3 references other previously discussed standards such as: EOTA ETAG 001 ICCES AC308 ACI 355.2 07 Short Term Incremental Loading Test for Adhesive Anchors ASTM E488 provides for two load rates in the short term tension test; a continuous load rate that will produce failure at around two minutes and an incremental load rate that loads at 15% intervals and holds each step for two minutes. Several short term tension tests were conducted at the University of Florida under NCHRP Project 2007/Task 25 5 using a modified incremental load rate. Figure 2 14 shows a sample anchor test loaded with the incremental load rate. Under the incremental load rate, it was noticed that at the lower stress levels the anchor would initially displace when the load was held constant but would eventually stabilize over the two minute interval. However, at the higher stress levels, some anchors would continue to displace over the two minute interval.

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103 Stress Versus Timeto Failure Test NCHRP (2009) investigated sustained load testing for adhesive anchors and recommended a stress versus timeto failure test method for AASHTO and has been adopted as AASHTO (2010c) TP 84 10. The following is a summary of that test method, more detailed information is presented in NCHRP (2009). The test method begins by placing five specimens under confined short term tension tests to determine the mean short term load (MSL) at an el evated temperature of 110F (43C). Subsequent sustained load test series are conducted on five specimens at two lower stress levels at an elevated temperature of 110F (43C). It was recommended that these lower stress levels be within the specified ranges of 70% to 80% and 60% to 70% of MSL Ideally, the stress levels chosen would create data points in separate log cycles. The sustained load tests are conducted until failure which i s defined as the initiation of tertiary creep. The data is plotted on a stress versus time to failure graph (semi log plot). A least squares trendline is drawn through each data point and projected linearly (on the log scale). According to Klompen et al. (2005), most polymers show a linear relationship between the logarith m of increasing timeto failure and decreasing stress however, some polymers do exhibit a lower bound stress level. While a linear projection would be sufficient and possibly conservative, a manufacturer can perform longer term tests at lower stress levels in order to better define the curve. See Figure 2 15 for a sample Stress versus Timeto Failure graph. The test data can also be summarized in a ta ble of estimated failure loads at specified structure lifetimes.

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104 NCHRP (2009) indicates that the stress versus timeto failure test method provides a viable means for evaluating the sustained load performance of adhesive anchors. This method was adopted as the primary method of assessing a parameters influence on sustained load performance for this project. A detailed discussion of how this method was implemented is described later. Adhesive Alone Tests Adhesive alone tests involve testing the adhesive without the concrete and anchor. This approach could be simpler, cheaper, and quicker than tests that involve the entire adhesive anchor system installed in concrete. It is understood that the interaction of the adhesive with the concrete is an important variable to creep resistance and is essential to be included in the testing. Therefore, it was not reasonable to only test the adhesive alone for the evaluation of short term and sustained load performance of adhesive anchors in concrete, but such tests were included in the project since they could possibly serve as: Q ualifying or prescreening tests prior to further more expensive/timely testing F ingerprinting tests to confirm the identity of an adhesive on site. C omparison tests between adhesives Time t emperature s uperposition and m aster c urves Time Temperature Superposition is the idea that a change in temperature produces the same effect as a change in measurement time for a viscoelastic material. This proposal allows the researcher to conduct t ests on a sample over a range of temperatures and shift the results along the time axis until they superimpose, creating what is called a master curve, thereby providing predictions of the materials behavior over a broader range of time.

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105 Crawford (1998) explains that the glass transition temperature ( Tg) is usually taken as the reference temperature. If the properties of an adhesive are known at Tg, then the properties at any temperature can be determined. Per Hunston et al. (1980) this relationship is valid for materials with more simple chemistries, but may not be valid for more complex materials. Master curves are a common method of simplifying and presenting data dealing with time temperature equivalence and can be used to extend the data beyond the testing range. Vuoristo and Kuokkala (2002) conducted creep tests at different temperatures and used master curves to predict the behavior of an epoxy used on rolls in the paper making industry by expanding the data by two orders of magnitude. Master cur ves are also used in ASTM D2990 as an accepted method to predict sustained load properties of plastics. Time temperature superposition works well for polymers within the linear viscoelastic region where compliance is independent of stress. For materials w hose compliance increases as stress increases, timetemperature superposition is not appropriate. Figure 2 16 is a sample master curve created from str ess relaxation data. The left side of the figure shows the stress relaxation data for various temperatures. These curves were then shifted until they lined up and formed the master curve as shown on the right side of the figure. Time s tress s uperposition Time stress superposition is another method to create a master curve from several short term tests at a constant temperature at various stress levels. This approach is more practical for materials not within the linear viscoelastic region where the

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106 compl iance changes as stress changes. Tests are conducted on a sample at a constant temperature over a range of stress levels. Similar to timetemperature superposition, the curves can be shifted along the time axis to create a master curve at a particular st ress level ( Figure 2 17 Figure 2 18). For strains in the linear viscoelasti c range, the time temperature superposition principle works well. However, the timetemperature superposition principle only relates the temperature to time and if the strain or stress is large enough to change the speed of the underlying molecular motion mechanism or even alter the mechanism, the predicted time response from only using the timetemperature superposition principle will not be accurate. A few theories tried to address this issue by assuming that there were no changes in the underlying mechanism and only the stress or strain altered the speed. Using such an approach, a stress or strain shift factor can also be introduced. The time stress superposition shows satisfactory results for a few polymer systems but its validity needs to be verified for each material. Dynamic Mechanical Thermal Analysis (DMTA) tests Dynamic Mechanical Thermal Analysis (DMTA) tests take thin samples of an adhesive and subject them to many cycles of a tensile load. Chin et al. (2007) conducted DMTA tests on two adhes ives in which tensile strain sweeps were conducted at different temperatures and the test data was used to perform a timetemperature superposition. The storage modulus (E), loss modulus (E), and tan delta (E/E) were calculated and master curves were generated for both adhesives. Figure 2 19 and Figure 2 20 present the E, E and tan delta curves (respectively) generated by t he researchers.

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107 Creep c ompliance c urves Creep compliance is defined as the strain due to creep divided by stress. Creep compliance curves are plotted versus time and since the strain is normalized by stress, these curves provide an indication of displacem ent versus time and can be used to show a materials creep deformation properties over time. In the National Institute of Standards and Technology (NIST) study by Chin et al. (2007), creep compliance curves were generated which displayed the predicted creep behavior of two adhesives over time. Figure 2 21 clearly illustrates that the two adhesives tested are predicted to have different creep properties. Chin et al. (2007) warn that these estimated creep compliance curves are not a substitute for the direct measurement of creep behavior because they are limited to the linear viscoelastic region and adhesive anchors under sustained loading may functio n in the nonlinear region, especially as failure is approached. However, they can be valuable as prescreening tools to indicate which adhesives warrant further/more exact testing. California Department of Transportation (CALTRANS) TM 438 CALTRANS (2006a) TM 438 determines rheological properties of adhesives using a Dynamic Shear Rheometer (DSR). This test method, also confined to the linear viscoelastic range as discussed above, cannot be used as a direct measurement of creep performance, but might be able to be used as a prescreening test. Tensile c reep t ests ASTM D2990 provides the testing procedure for a tensile creep test. Tens ile creep tests load small dog bone specimens of adhesive using the dimensions for Type I or Type II dog bones as specified in ASTM D638 ( Figure 2 22). Two specimens are required for each stress level tested or three specimens if fewer than four stress levels

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108 are used. A m inimum of three stress levels is recommended for materials that show linear viscoelasticity and at least five stress levels for materials that are significantly affected by stress. ASTM D2990, specifies that the tensile creep specimens are loaded to the gi ven stress level within five seconds. Measurements of extension, temperature, and humidity are recorded at progressively longer time intervals. ASTM D2990 suggests the following approximate time schedule: 1, 6, 12, and 30 min; 1, 2, 5, 20, 50, 100, 200, 500, 700, and 1000 hours; and monthly beyond 1000 hours. The tests are continued until failure. Test series can be conducted under different testing conditions (temperature, humidity, cure time) to evaluate the effect of a parameter on the adhesives creep performance. To determine the 100% stress level (mean short term strength), short term load tests on five specimens are conducted per the procedure specified in ASTM D638. ASTM D638 specifies a constant strain loading rate that produces failure between 30 seconds and five minutes. NCHRP (2009) recommends that both the short term load tests and the sustained load tests must be loaded with the same load transfer duration. It is recommended that the load transfer duration of both the ASTM D638 short term load tests and the ASTM D2990 tensile creep tests be set at 21 minutes, as specified for the short term load tests and sustained load tests for anchor pullout tests. Design G uidelines and S pecifications R elated to A dhesive A nchor S ystems The review of design guidelines and specifications related to adhesive anchors included national standards, state DOT standards, and international standards. The

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109 test methods and specifications described above generate design values (e.g. bond stress) tha t are used in the design calculations described below. ICCES AC308 Acceptance Criteria for Post Installed Adhesive Anchors in Concrete Elements ICCES AC308 provides both ASD and LRFD design provisions. Only the LRFD method will be addressed in this report. The ICC ES AC308 LRFD (strength design) method presented in ICC ES AC308 3.3 provided the basis for development of the adhesive anchor provisions in ACI 31811 Appendix D. ACI 355.411 does not include design provisions. The design methodology prov ided in ICC ES AC308 is discussed under ACI 31811. ACI 31811 Building Code Requirements for Structural Concrete ACI 318 11 Appendix D addresses anchorage to concrete and incorporated the design provisions for adhesive anchors developed by ICC ES AC308 in 2011 A general overview of adhesive anchor provisions is presented below. ACI 318 11 Appendix D specifies various strength reduction factors ( ) depending on type of failure, steel element (brittle or ductile), presence of supplementary reinforcement, and category as defined by ACI 355.207 The strength reduction factors range from 0.45 to 0.75. Tension ACI 318 11 Appendix D considers the following design strengths (failure modes) for anchors in tension and are illustrated in Figure 2 23: Steel strength of anchor in tension Concrete breakout strength of anchor in tension Pullout strength of cast in, post installed expansion or undercut anchor in tension Concrete sideface blowout strength of a headed anchor in tension Bond strength of adhesive anchor in tension

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110 Steel strength of anchor in tension. The nominal strength of the anchor in tension as governed by the steel ( Nsa) is determined by ACI 318 11 Equation D 2 : = where: A se,N effective cross section of a single anchor, in 2 f uta specified tensile strength of anchor steel, psi The value ( futa) must not exceed 1.9fya or 125,000 psi where fya is the specified yield strength of the anchor steel in psi. The 1.9fya limit is to ensure that yielding does not occur under service loads. Concrete breakout strength of anchor in tension. The nominal concrete breakout strength of a single anchor ( Ncb) or a group of anchors ( Ncbg) shall not exceed: Single anchor (ACI 318 11 Equation D 2) : = Group of anchors (ACI 31811 Equation D 4) : = , where: A Nc projected concrete failure area of a single anchor or a group of anchors that can be approximated as the base of a rectangle that is resulted by projecting the failure surface out 1.5 hef from the centerlines of the anchor or from the centerlines of the anchors in a group of adhesive anchors, in2 A Nco projected concrete failure area of a single anchor with edge distance equal or greater than 1.5hef, as specified in ACI 318 11 Equation D 5, in2

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111 = 9 h ef effective embedment depth of anchor, in ec,N modification factor for eccentricity of applied loads ed,N modification factor for edge effects c,N modification factor based on presence or absence of cracking cp,N modification factor for anchor in uncracked concrete without supplementary reinforcement N b the basic concrete breakout strength of a single anchor in tension in cracked concrete as specified in ACI 31811 Equation D 6, lbs = k c 17 for post installed anchors 24 for cast in place anchors a modification factor for lightweight concrete f c specified compressive strength, psi Pullout strength of cast in, post installed expansion or undercut anchor in tension. This failure mode does not apply to adhesive anchors. Concrete sideface blowout strength of a headed anchor in tension. This failure mode does not apply to adhesive anchors. Bond strength of adhesive anchor in tension. The nominal bond strength of a single adhesive anchor ( Na) or a group of adhesive anchors ( Nag) shall not exceed: Single anchor (ACI 318 11 Equation D 18) : = Group of anchors (ACI 31811 Equation D 19): = where:

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112 A Na projected influence area of a single adhesive anchor or a group of adhesive anchors that can be approximated as the base of a rectangle that is resulted by projecting the failure surf ace out cNa from the centerlines of the anchors in a group of adhesive anchors, in2 A Nao projected influence area of a single anchor with edge distance equal or greater than cNa as specified in A CI 318 11 Equation D 20 in2 = ( 2 ) c Na edge distance required to develop the full bond strength of a single adhesive anchor as specified in ACI 31811 Equation D 21 in = 10 d a nominal diameter of adhesive anchor, in uncr characteristic limiting bond stress of adhesive anchor in uncracked concrete, psi ec,Na modification factor for eccentricity of applied loads ed,Na modification factor for edge effects cp,Na modification factor for anchor in uncracked concrete without supplementary reinforcement N ba the basic bon d strength of a single adhesive anchor in tension in cracked concrete as specified in ACI 31811 Equation D 22, lbs = a modification factor for lightweight concrete cr characteristic limiting bond stress of adhesive anchor in cracked concrete, psi h ef effective embedment depth of anchor, in

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113 If test results for cr from ACI 355.411 are not available, then the values in Table 2 7 for cr and uncr can be used. Note that the values in Table 2 7 are multiplied by 0.4 if the anchor is subject to sustained tension lading. The nominal tension strength ( Nn) is then the lesser of Nsa, Ncb, Na for single adhesive anchors or Nsa, Ncbg, Nag for a group of adhesive anchors. In addition, per ACI 31811 D.4.1.2, a 55% limitation is placed on the anchor in a connection that resists the highest sustained load. Shear ACI 318 11 Appendix D considers the following design strengths (failure modes) fo r anchors in shear and are illustrated in Figure 2 24: Steel strength of anchor in shear Concrete breakout strength of anchor in shear Concrete pry out strength anchor in shear Steel strength of anchor in shear. The nominal strength of an anchor in shear as governed by the steel ( Vsa) is determined in ACI 318 11 Equation D 29 as: = 0 60 where: A se ,V effective cross section of a single anchor in shear, in 2 f uta specified tensile strength of anchor steel, psi The value ( futa) must not exceed 1.9fya or 125,000 psi where fya is the specified yield strength of the anchor steel in psi. The 1.9fya limit is to ensure that yielding does not occur under service loads. Concrete breakout strength of anchor in shear. The nominal concrete breakout strength of a single anchor ( Vcb) or a group of anchors ( Vcbg) in shear shall not exceed:

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114 Single anchor (ACI 318 11 Equation D 30) : = Group of anchors (ACI 31811 Equation D 31) : = , where: A Vc projected area of the failure surface on the side of the concrete member at its edge for a single anchor or group of anchors, in2 A Vco projected area for a single anchor in a deep member with a distance from the edge greater than 1.5ca1 in the direction of the shear force as specified in ACI 318 11 Equation D 32, in2 = 4 5 ( ) c a1 distance from the center of the anchor to edge of the member in the direction of the shear load, in ec,V modification factor for eccentricity of applied loads ed,V modification factor for edge effects c,V modification factor based on presence or absence of cracking h,V modification factor for anchor in concrete where the member thickness is less than 1.5 ca1 V b the basic concrete breakout strength of a single anchor in shear in cracked concrete is the les ser of ACI 31811 Equation D 33 and ACI 318 11 Equation D 34 lbs = 7 ( ) = 9 ( ) l e load bearing length of anchor, in d a nominal diameter of adhesive anchor, in

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115 a modification factor for lightweight concrete cf specified compressive strength, psi Concrete pry out strength of anchor in shear. The nominal pryout strength of a single anchor ( Vcp) or a group of anchors ( Vcpg) in shear shall not exceed: Single anchor (ACI 318 11 Equation D 40) : = Group of anchors (ACI 31811 Equation D 41) : = where: k cp 1.0 for h ef < 2.5 in k cp 2.0 for h ef N cb nominal concrete breakout strength of a single anchor, lbs N cbg nominal concrete breakout strength of a group of anchors, lbs The nominal shear strength ( Vn) is then the lesser of Vsa, Vcb, Vcp for single adhesive anchors or Vsa, Vcbg, Vcpg for a group of adhesive anchors. Tension and s hear i nteraction ACI 318 11 Appendix D uses a tri linear approach to tensionshear interaction expressed in ACI 318 11 Equation D 32 with two conditions: + 1 2 but: if V ua 0.2 then full strength in tension can be used if N ua 0.2 then full strength in shear can be used where: N ua factored tension force, lbs

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116 N n nominal strength in tension, lbs V ua factored shear force, lbs V n nominal strength in shear, lbs strength reduction factor AASHTO LRFD Bridge Design Specifications AASHTO (20 10b) was reviewed for a framework of design specifications related to general anchor bolt design within which the epoxy adhesive design standards could be incorporated. Article 14.8.3 Anchorages and Anchor Bolts presents the design requirements for anchor bolts. It refers to article 6.13.2.10.2 for the tensile resistance, article 6.13.2.12 for the shear resistance, and article 6.13.2.11 for combined tensionshear resistance. These three references to S ection 6 only evaluate the resistance of the bolt and do not consider concrete failure. Article 5.7.5 addresses the bearing resistance of the concrete, but there is no provision for concrete breakout and sideface blowout in tension and concrete breakout and pry out failure in shear. The commentary in C14.8.3.1 refers the designer to ACI 31811 Appendix D for global design of anchorages. AASHTO Standard Specifications for Structural Supports for Highway Signs, Luminaires and Traffic Signals Article 5.17 of AASHTO (2009) w as also investigated for a possible anchor bolt design framework in which to incorporate adhesive anchors. AASHTO (2009) provides ASD design guidelines for cast in place anchor bolts. No provision is made for adhesive anchors. To ensure a ductile failur e, anchor bolts must be designed so that they reach their minimum tensile strength prior to concrete failure. It specifies that the following failure modes be addressed: Bolt failure

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117 Load transfer from anchor to concrete Concrete tensile strength Lateral bursting of concrete Base plate failure The ASD design provisions in Article 5.17 were adapted from NCHRP (2002). AASHTO (2009) mainly addresses the design of the anchor bolt itself and provides ASD equations for allowable tension, compression, and shear stresses on the bolt as well as interaction equations for combined tension and shear and combined compression and shear. Bending stresses are considered for doublenut anchor bolt connections if the clearance between the bottom of the leveling nuts and t he top of the concrete exceeds one bolt diameter. While outside of the scope of AASHTO (2009), it recommends other design considerations such as: Block shear rupture Shear lag Prying action Base plate stiffness NCHRP Report 469 Fatigue Resistant Design of Cantilevered Signal, Sign, and Light Supports NCHRP (2002) includes a Recommended Anchor Rod Specification and Commentary as Appendix A of the report. The specification is for the design, installation, and inspection of cast in place anchor rods and does not cover post installed anchors, but allows them as alternative design anchors. NCHRP (2002) uses an LRFD approach and designs anc hor bolts for tensile strength, compressive strength, shear strength, combined tension and shear, bearing at anchor rod shear holes, and tensile fatigue. The American Concrete Institute (ACI) is referred to for concrete design.

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118 NYSDOT Bridge Design Manual NYSDOT (2008a) refers to AASHTO (2010b) .8.3 for the design of anchor bolts. NYSDOT (2008a) 6.8.5.4 allows for post installed grouted anchors which are allowed for rehabilitation projects and recommends that proof load tests be conducted. It further recommends an embedment depth of 12 for 1 diameter bolts. FDOT Structures Manual Section 1.6 of volume 1 of FDOT (2009) provides design guidelines for adhesive anchors. FDOT does not allow adhesive anchors for overhead or upwardly inclined holes. Furth ermore, adhesive anchors are not allowed for loading conditions with a predominately sustained load. A predominately sustained load is defined as a load where the permanent portion of the factored tension load exceeds 30%. The reduction factors ( ) specified by FDOT are as follows: c = 0.85 for adhesive anchors controlled by concrete embedment c = 1.00 for extreme events s = 0.90 for adhesive anchors controlled by anchor steel The following design requirements are specified by FDOT: Tension FDOT considers the following design strengths for anchors in tension: Tensile strength controlled by anchor steel. The design tension strength controlled by anchor steel ( Ns) is defined in FDOT Equation 1 2 as: = where: strength reduction factor A e effective tensile stress area of steel anchor (may be 75%

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119 of gross area for threaded anchors), in 2 f y minimum specified yield strength of steel, ksi Tensile strength controlled by adhesive bond. The design tension strength controlled by adhesive bond ( Nc) is defined in FDOT Equation 13 as: = where: strength reduction factor e modification factor to account for edge distances gn modification factor for groups N o nominal tensile strength of adhesive bond as specified in FDOT Equation 14 kips = T nominal bond strength of adhesive product, ksi T = 1.08 ksi for type V and HV adhesive product on FDOT QPL T = 1.83 ksi for type HSHV adhesive product on FDOT QPL d nominal diameter of adhesive anchor, in h e anchor embedment depth, in The design tension strength ( Nn) is the smaller of Ns and Nc Shear FDOT considers the following design strengths for anchors in shear: Shear strength controlled by anchor steel. The design shear strength controlled by anchor steel ( ) is defined in FDOT Equation 17 as: = 0 7 where: strength reduction factor A e effective tensile stress area of steel anchor (may be 75% of gross area for threaded anchors), in2 f y minimum specified yield strength of steel, ksi

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120 Shear strength controlled by concrete breakout. The design shear strength controlled by concrete breakout ( ) is defined in FDOT Equation 18 as: = 0 4534 where: strength reduction factor gv modification factor for groups c anchor edge distance from center of anchor to free edge, in cf minimum specified compressive strength of concrete, ksi The design shear strength ( ) is the smaller of and Tension and s hear i nteraction FDOT uses a linear approach to tensionshear inter action expressed in FDOT Equation 110: + 1 0 where: N u factored tension load, kips N n design tension strength, kips V u factored shear load, kips V n design shear strength, kips strength reduction factor IDOT Bridge Manual The only reference to anchor bolt design in IDOT (2008) was found in section 3.7.3 which addresses seismic design of bridge bearings. The design approach taken by IDOT for bridge bearing during seismic events is to prevent the loss of span. Loss of span is prevented by adequately detailing seat widths and span lengths. Connection elements or anchor bolts are designed to fail at a certain level of acceleration. When

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121 the connection elements fail, the bearing seat width or span length must be large enough to prevent loss of span. In this design approach, the anchor bolts are only designed for shear. The number of anchor bolts is determined by dividing the base shear at the bearing by the allowable shear force per anchor. When soil conditions are poor or it is not possible to enlarge seat lengths, the anchor bolts must be designed to remain elastic during the seismic event. In this situation, the anchor bolts must be designed for combined shear and tension. The only specific reference to epoxy anchor bolts is made in section 3.7.4 which address the conversion of an existing abutment into a semi integral abutment. PENNDOT Design Manual Part 4 Structures PENNDOT (2007) Part 4 Structures 3.6.4.9 refers to 5.17 and 5.12 of AASHTO (2009) for the design of anchor bolts. PENNDOT (2007) has restrictions on the use of adhesive anchors. Section 3.6.8 addresses adhesive anchor design in general and states that adhesive anchors are not allowed in tension applications for permanent installations. Section 3.6.4.9 addresses the anchor bolt design for sound barrier walls and specifically does not permit adhesive anchors. Section 5.5 pertains to bridge rehabilitation strategies and provides a detail in section 5.5.2.4 (Figure 5.5.2.44) for a repair of expansion dams using adhesive anchors for cases in which the bolts were sheared off. WSDOT Bridge Design Manual WSDOT (2008a) 1 0.1.2 Bridge Mounted Signs specifically mentions using resin bonded anchors in new and existing structures. The anchors must be installed per the

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122 manufacturers specifications in dry concrete and the nuts must be torqued to the proof load. MDOT Bridge Design Manual MDOT (2005) 7.06.02 provides design guidelines for bonded anchors. The embedment depth for A307 bolts is nine times the nominal anchor diameter. Bonded anchors are designed for tension and shear, but only steel failure is addressed. The allowable tension and shear loads are defined as follows: Allowable tensile load = Allowable shear load = 0 30 where: A T tensile stress area (net section through threads) f y yield strength FS factor of safety = 4 Adhesive anchors are specifically prohibited in overhead applications with a sustained tension load. MDOT Moratorium on the U se of Adhesive Anchors in Sustained Tensile LoadOnly Overhead Applications MDOT (2008) imposed a moratorium on overhead sustainedtension loading applications. VDOT IIM S&B40.2 Sound Barrier Wall Attachments VDOT (2007) prohibits using adhesive anchors in attaching structure moun ted walls.

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123 VDOT IIM S&B76.2 Adhesive Anchors for Structural Applications VDOT (2008) limits the use of adhesive anchor to shear loading only. It specifically prohibits using adhesive anchors in applications of sustained, cyclical, and fatigue tension loadings. EOTA ETAG 001 Annex C Design Methods for Anchorages Annex C of EOTA (1997b) presents a design methodology for bonded anchors. This technical approval document was created in 1997 and has undergone several amendments. EOTA (1997b) served as the basis for the adhesive anchor provisions in ACI 318 11 Appendix D. A review of EOTA ( 1997b) did not produce any new information than what was already discussed with ACI 31811 Appendix D. fib Design of Anchorages in Concrete fib (2011) has design methodology for adhesive anchors subject to tension and shear loading. The design methodology is only applicable for anchors with a predominate short term load. Part 3 presents both elastic and plastic design procedures summarized in two flowcharts. Most of the calculations are similar to those presented by ACI 31811. Tension The design procedure for tensile resistance evaluates the following resistances. Steel resistance. The equation to calculate steel resistance is similar to ACI 318 11 Eq uation D 3. Concrete pullout resistance. The characteristic resistance of a combined pullout and cone f ailure ( NRk,p) is as follows in fib Equation 16.21 : = , where:

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124 characteristic bond resi stance similar to ACI 318 11 Equation D 22 A,Np modification factor due to geometric effects, comparable to the factor in ACI 318 11 Appendix D s,Np modification factor due to edge effects, comparable to ed,N in ACI 31811 Appendix D g,Np modification factor accounting for the failure surface of groups. Often this is neglected for simplification. ec,Np modification factor due to eccentricity effects in groups, comparable to ec,Na in ACI 31811 Appendix D re,Np modification factor due to shell spalling in cases of low embedment depth and closely spaced reinforcement Concrete cone resistance. The characteristic resistance of an anchor or group of anchors due to cone failure ( NRk,c) is as follows in fib Equation 10.12 : = , where: characteristic resi stance similar to ACI 318 11 Equation D 6 A,N modification factor due to geometric effects, comparable to the factor in ACI 318 11 Appendix D s,N modification factor due to edge effects, comparable to ed,N in ACI 31811 Appendix D ec,N modification factor due to eccentricity effects in groups, comparable to ec,N in ACI 318 11 Appendix D re,N modification factor due to shell spalling in cases of low embedment depth and closely spaced reinforcement

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125 Concrete splitting. The characteristic resistance of an anchor or group of anchors due to splitting failure is calculated using fib Equation 10.1 2 with an additional modification factor ( h,sp) to account for the influence of member thickness. Shear The design procedure for shear resistance evaluates the following resistances. Steel resistance. The equation to calculate steel resist ance is similar to ACI 318 11 Equation D 29 except it specifies a c onstant of 0.5 instead of 0.6. Concrete pryout resistance. The equation to calculate concrete pryout resi stance is similar to ACI 318 11 Equation D 40 and Equation D 41. Concrete edge resistance. The characteristic resistance of an anchor or group of anc hors close to an edge ( VRk,c) is as follows in fib Equation 10.2 5 : = , where: characteristic resi stance similar to ACI 318 11 Equation D 33 A,V modification factor due to geometric effects, comparable to the factor in ACI 318 11 Appendix D h,V modification factor due to edge effects, comparable to h,V in ACI 318 11 Appendix D s,V modification factor due to edge effects, compara ble to ed,V in ACI 318 11 Appendix D ec,V modification factor due to eccentricity effects in groups, comparable to ec,V in ACI 318 11 Appendix D modification factor to take into account the angle of the applied load re,V modification factor due to type of edge reinforcement used

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126 Tension and s hear i nteraction fib (2011) uses a tri linear approach to tensionshear interaction similar to that found in ACI 31811 Appendix D. Quality Assurance Guidelines and Construction Specifications Related to Ad hesive Anchor Systems The review of quality assurance guidelines and construction specifications related to adhesive anchors included national standards, state DOT standards, and internat ional standards. Manufacturer Printed Installation Instructions (MPI I) were also reviewed for an understanding of what is typically required in adhesive anchor installations. ICCES AC308 Acceptance Criteria for Post Installed Adhesive Anchors in Concrete Elements ICCES AC308 4 includes quality assurance guidelines for the inspector of adhesive anchor installations. Since ACI 355.411 was developed from ICC ES AC308, the provisions set forth in ICC ES AC308 will not be discussed, but will be addressed under the discussion of ACI 355.411. ACI 355.411 Qualification of Post Installed Adhesive Anchors in Concrete ACI 355.411 presents a quality assurance program for the inspector of post installed adhesive anchors. ACI 355.411 specifies the quality assurance requirements. Manufacturers must have an approved quality assurance program with a quality control manual for each product. Manufacturers must undergo unannounced inspections according to the requirements of ISO/IEC 17011 by an inspection agency under ISO/IEC 17020. Manufacturers must supply inspection manuals for each product and anchors must be installed with special inspection in accordance with the building code and ACI 355.411.

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127 When required, continuous special inspection shall be conducted in which all aspects of the installation must be inspected by an inspector. However, holes can be drilled without an inspector present as long as the inspector inspects the drill bit and verifies the hole sizes. The following must be verified: hole drilling method in accordance with the manufacturers specifications hole location, diameter, and depth hole cleaning per the manufacturers specifications anchor type, material, diameter, and length adhesive identification and expiration date installation in accordance with the manuf acturers specifications When required, periodic special inspections shall be conducted in which the inspector inspects all aspects listed above for each anchor type for the same construction personnel. Only the initial installation needs to be inspected and the rest can be installed without the inspector as long as the same product is installed by the same personnel. For long construction projects, the inspector should regularly verify that the adhesive product is being installed correctly. When require d, a proof loading program should be conducted which includes the following: frequency of proof loading based on anchor type, diameter and embedment depth proof loads by anchor type, diameter, and location acceptable displacement at proof load action taken to remediate a case of excessive displacement or the failure to achieve the proof load Proof load tests should be confined tension tests with the proof load not exceeding 50% of the expected ultimate load based on adhesive bond strength nor 80% of the anc hor yield strength.

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128 AASHTO LRFD Bridge Construction Specifications AASHTO (2010a) 8.9 addresses anchor bolts for bearing devices and only references cast in or grouted anchor bolts. AASHTO (2010a) 29 specifically mentions adhesive anchors and requires t hat they be prequalified by universal test standards. The user is encouraged to follow the MPII for drilling and only allows core drilling if it is specified by the manufacturer or anchors have been tested in core drilled holes. Core drills are allowed t o cut rebar. The user is referred to the MPII for proper cleaning procedures. This section provides for sacrificial and proof load testing and guidance on torquei ng of the anchor bolts. AASHTO Standard Specifications for Structural Supports for Highway S igns, Luminaires and Traffic Signals AASHTO (2009) .17.5 specifies that anchor bolts must be installed with sufficient length, cover, and anchorage in concrete to ensure a ductile failure. Additionally, AASHTO (2009) places a limit on misalignment of 1: 40 from vertical for anchor bolt installation. NCHRP Report 469 Fatigue Resistant Design of Cantilevered Signal, Sign, and Light Supports NCHRP (2002) includes a Recommended Anchor Rod Specification and Commentary as Appendix A of the report. The specif ication provides guidance for installation and construction inspection. While this report only addresses cast in place anchors and not adhesive anchors, most of the information covers the casting of anchor bolts in concrete and tightening of the anchor bolt following concrete curing. The specification provides guidance for straightening a misaligned bolt. The maximum misalignment allowed is 1:40 from vertical. If an anchor bolt does not exceed

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129 a misalignment of 1:20 from vertical it can be straightened by hitting it with a hammer or bending it with a jack or pipe. CALTRANS Standard Specifications CALTRANS (2006b) 75 refers to the manufacturers specifications for installation requirements. Anchors must be installed such that the equipment attached to i t will bear firmly against the concrete. If there is no mention in the manufacturers instructions regarding the installation torque, the anchors should be torqued to the values listed in Table 2 8 TxDOT Standard Specifications for Construction and Maintenance of Highways, Streets, and Bridges TxDOT addresses the installation of anchor bolts in TxDOT (2004) 420.4. For epoxy installations it specifies a hole diamete r of 1/16 to greater than the anchor diameter. For prepackaged systems, it requires that the manufacturers cleaning instructions be followed exactly. A procedure must be established for the cleaning and preparation of the holes which includes cleani ng the holes of loose material, grease, oil and other substances. The holes should be blown with filtered compressed air and be in a dry condition prior to installation. The space between the anchor and the sides of the hole must be completely filled wit h adhesive. Section 420.4 specifies a Type III adhesive per TxDOT (2007a) DMS 6100 for neat epoxies and Type VIII for epoxy grout. NYSDOT Standard Specifications NYSDOT (2008c) 586 2.01 Drilling and Grouting Bolts restricts the use of adhesive anchors i n overhead installations or for applications with a sustained tensile load.

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130 NYSDOT (2008c) 586 3.01 Drilling and Grouting Bolts specifies the installation requirements for adhesive anchors. A rotary impact drill should be used but if reinforcement is e ncountered during drilling, a core drill can be used only to cut the rebar, and the rotary impact drill used for the remainder of the drilling. Lubricants cannot be used during drilling and drilling should not cause damage to concrete. Prior to installat ion, the holes must be dry and clean of loose material. The bolts should be inserted the full depth of the hole and jiggled to ensure complete coverage by the adhesive. Excess adhesive should be struck off flush with the surface. Horizontal installation s are allowed and care should be taken to ensure that the adhesive does not run out of the hole. NYSDOT (2008c) 586 3.02 Pullout Testing specifies the requirements for pullout testing. A table is provided in the specification to determine the number of anchors to test depending on lot size. The load applied should not exceed 90% of the ASTM proof load (ASTM A568 for anchor bolts and ASTM A615 for reinforcing bars) or 90% of the anchor yield strength if the ASTM proof load is not given. The test is sto pped upon reaching the test load. Anchors pass the test if they can attain the load without permanently displacing. NYSDOT (2008c) 586 includes the changes addressed by NYSDOT (2008b) discussed earlier. FDOT Standard Specifications for Road and Bridge Construction FDOT (2007) 416 Installing AdhesiveBonded Anchors and Dowels for Structur al Applications specifies that the installation of adhesive anchors and the equipment used for the installation must be in accordance with the manufacturers specifications. FDOT only allows an adhesive anchor product that meets FDOT (2007) 937 and is included

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131 in the Qualified Pr oducts List (QPL) maintained by the state. The following requirements pertain to the installation of adhesive anchors: Install in structurally sound concrete member free of cracks in the area of the anchor. Use a rotary hammer drill and carbide bit unless otherwise specified by the manufacturer. The hole diameter must be greater than 105% and less than 150% of the anchor diameter. Clean the hole according to the manufacturers requirements but as a minimum blow with compressed air, then brush, and blow again with compressed air. Use only a nonmetallic brush to prevent polishing the hole. Follow the manufacturers requirements regarding limits on anchor position, dampness, ambient temperature, and curing time. Fill the hole with the adhesive such that it is within of concrete surface after placement of anchor. IDOT Standard Specifications for Road and Bridge Construction IDOT (2007b) 509.06 Setting Anchor Rods requires that the holes be drilled to the diameter and depth specified by the manufacturer. The rods should be set with capsule or cartridge systems previously approved by the state and installed per the manufacturers instructions. IDOT (2007b) 521.06 Anchor Bolts, Rods, and Side Retainers requires verification of the holes for depth and diam eter prior to installation. Holes are required to be kept dry and to be blown clean prior to installation. Following installation, the top of the bolt shall be measured in order to determine proper embedment. The anchor bolts should allow for to 2 above the top of the nut.

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132 WSDOT Construction Manual WSDOT (2009) 6 3.2C Use of Epoxy Resins warn s the user against viewing epoxy resins as a cure all for bonding applications due to their inherent limitations. Specific caution is mentioned regarding usi ng epoxy resins below 50F (10C). Several guidelines are provided for the inspector of epoxy resin systems: Epoxy resin must be completely mixed Verify the temperature and/or moisture limitations of the epoxy resin Area should be cleaned and prepared according to the manufacturers specifications prior to installation The epoxy should completely fill the space around the anchor The material portion of WSDOT (2009) includes 9 4.60 which addresses Epoxy Systems and 9 4.61 for Resin Bonded Anchors. WSDOT (2009) 9 4.61 refers to a Qualified Products List (QPL) maintained by the state for material approval. If a resin bonded anchor system is not on the QPL, test results from ASTM E488 and manufacturers certificate of compliance can be submitted for approval. MDOT Standard Specifications for Construction MDOT (2003) 712 B ridge Rehabilitation Concrete allows the installation of adhesive anchoring of bars in vertical and horizontal applications. EOTA ETAG 001 Part 1 of EOTA (1997a) does not provide much information regarding quality assurance or construction specifications. Reference is made to the manufacturers installation requirements, but limits the installation to a temperature range of 23F to 104F ( 5C to 40C).

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133 Part 5 of EOTA (2002) all ows for installation in dry, wet, and flooded holes. It also specifies that the holes are to be drilled as specified by the manufacturer. Manufacturers Printed I nstallation Instructions Due to the fact that many specifications refer to the Manufacturers Printed Installation Instructions (MPII), the installation requirements from three different products (names withheld) have been included to serve as a reference for what is typically specified by manufacturers. The manufacturers and the products chosen were not necessarily what were used in the testing program of this research project. MPII contain information regarding storage conditions (temperature and humidity ranges) and warnings to check that the expiration date has not passed prior to installation There are many similarities amongst MPII Most include instructions on cleaning the hole which can include blowing with compressed air and brushing. There is usually a procedure to confirm that the adhesive is thoroughly mixed, by number of squeezes of the applicator or visually inspecting the color of the adhesive. Additionally, there is a process for injecting the adhesive in the hole to avoid air voids. And finally there are instructions for inserting the anchor. Manufacturer X This product is an e poxy resin with quartz and titanium dioxide. the anchor diameter. The hole is then blown out using a nozzle and 80 psi (minimum) oilfree compressed air for four seconds. The hole is then brushed up and down four times with a nylon brush. And finally the hole is blown for another four seconds with compressed air.

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134 The adhesive is discharged using a cartridge and self mixing nozzle. Initially the adhesive is discharged to the side until the discharge has a uniform color signifying complete mixing. The hole is filled by inserting the nozzle to the bottom and discharging the adhesive. The nozzle is extracted as the hole fills in order to avoid the formation of air voids. water filled holes in order to remove all the water. The clean oil free anchor is installed in the hole while slowly turning it until it contacts the bottom of the hole. The a nchor should not be disturbed until the adhesive has fully cured. Horizontal and overhead installations are allowed and the installation is the same, except that a retaining cap is placed over the hole to keep the adhesive within the hole. Manufacturer Y T his product is an epoxy resin with an amine hardener. The hole is drilled with a rotary hammer drill and a drill bit confirming to ANSI B212.15.1994. The drill bit diameter is equal to the rod diameter plus 1/16 for anchor installations only. The hole is cleaned with 50 psi to 100 psi compressed air starting at the bottom using a nozzle and os cillating the nozzle in and out of the hole four times for a total of four seconds. If the hole is filled with water or sludge, the hole can be cleaned with pressurized water. The hole is then cleaned with a brush by inserting the brush into the hole in a clockwise fashion. The brush is turned one complete revolution for each of depth. Once the brush has reached the bottom, the brush is turned four complete times. The

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135 brush is then removed from the hole by rotating it one complete revolution for ever y of depth. Alternatively, the brush can be attached to a drill. The hole is then blown with compressed air or flushed with pressurized water as before. The adhesive is discharged and discarded from the cartridge tool until the adhesive is of a unifor m color. The nozzle is inserted to the bottom of the hole and slowly pulled out while discharging in a circular motion maintaining the tip of the nozzle under the level of the adhesive. The hole is filled to 60% full. For holes underwater, the hole is f illed entirely with adhesive thereby displacing all the water. The concrete must be between 50F (10C) and 110F (43C) during installation. The anchor is inserted in a counterclockwise motion and jiggled to remove air pockets. The anchor must not be di sturbed during working time until the cure time has elapsed. Manufacturer Z This product is a hybrid with methacrylate hardener, cementitious material, and quartz filler. The hole is drilled with a carbide bit to the proper depth and diameter. The hole is then cleaned with 80 psi compressed air using a nozzle inserted to the bottom of the hole. The hole is cleaned three times with a wire brush that is twisted while inserting. The hole is then blown with compressed air again. For holes with standing water, the hole must be flushed with water, brushed, and then flushed with water again. The standing water must be removed prior to inserting the adhesive. Depending on the size of the cartridge, the adhesive from the first two or three trigger pulls are disc arded (four trigger pulls are discarded if the temperature is below

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136 full. The anchor rod is inserted while twisting and can be adjusted during the specified gel time. The anchor should not be disturbed between the gel time and the cure time. Summary This chapter summarized the findings from the literature review which investigated the parameters that can influence bond strength as well as test methods and material spec ifications, design guidelines and specifications, and quality assurance guidelines and construction specifications related to adhesive anchors in concrete. One of the significant limitations of the stateof the art in adhesive anchors is the effect of var ious installation and inservice parameters on the sustained load performance of adhesive anchors. C hapter 3 presents the test program developed to address that limitation.

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137 Table 2 1 ACI 355.411 (2011) Table 8.1 Minimum test temperatures Temperature category Long term test t emperature a T lt Short term test t emperature a T st ( F ) ( C ) ( F ) ( C ) A 110 43 176 80 B lt + 20 lt + 11 a All test temperatures have a minus tolerance of 0 Table 2 2 CALTRANS (2001) CTM681 s ustained l oad v alues Stud d iameter (inches) Sustained t ension t est l oad (pounds) 1 31,000 1 17,900 14,400 5,000 4,100 3,200 2,100 1,000 Table 2 3 Performance requirements for type III adhesives tested with TxDOT (2007b) Tex 614J Physical p roperty Requirements Class A Class B Class C Gel Time, min. 25 min 25 min 6 min Viscosity of mixed components, poise (Pas) 1,200 (120) max 20 (2) min 150 (50) max Tensile Bond @ 6 hr., psi (Mpa) 200 (1.40) min 200 (1.40) min 200 (1.40) min Tensile Bond @ 120F (49C), psi (Mpa) 400 (2.8) min 400 (2.8) min 400 (2.8) min Thixotropy Bond @ 120F (49C), mils (mm) 30 (0.75) min 30 (0.75) min Wet Pullouta Strength, lbf. (kN) 4,500 (20) min 4,500 (20) min 4,500 (20) min a The wet pullout test determines the strength of the adhesive bond between a steel anchor and the surface of a hole in concrete or masonry units.

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138 Table 2 4 NYSDOT (2008b) chemical resistance requirements Chemical Resistance Gasoline Slight swell Hydraulic brake fluid No effect Motor Oil No effect Sodium Chloride (5%) No effect Calcium Chloride (5%) No effect Table 2 5 NYSDOT (2008b) anchor tests minimum pullout loads Concrete strength (psi) Minimum p ullout l oad (lbf) Test series 1 1 dia. 10 embedment Test series 2 4 embedment 51,120 8,593 4500 54,225 9,113 5000 57,150 9,630 5500 59,940 10,080 Table 2 6 FDOT (2000) FM 5 568 m inimum performance requirements for adhesive systems Test or p roperty Uniform b ond s tress Type HV adhesive (psi) Type HSHV adhesive (psi) Confined t ension 2290 3060 Damp h ole i nstallation 1680 1830 Elevated t emperature 2290 3060 Horizontal o rientation 2060 2060 Short t erm c ure 1710 1710 Specified b ond s trength 1080 1830 Table 2 7 ACI 318 11 (2011) c haracteristic bond stress to use in absence of test results Installation and service c onditions Moisture c ontent of concrete at t ime of a nchor i nstallation Peak in service temperature of concrete, (F) cr (psi) uncr (psi) Outdoor Dry to fully saturated 175 200 650 Indoor Dry 110 300 1000 Notes: Where anchor design includes sustained tension loading, multiply values of cr and uncr by 0.4. Where anchor design includes earthquake loads for structures assigned to Seismic Design Category C, D, E, or F, multiply values of cr by 0.8 and uncr by 0.4.

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139 Table 2 8 CALTRANS (2006b) installation torque values Stud d iameter (inches) Resin c apsule a nchors (foot pounds) 1 400 1 230 175 150 75 30 18

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140 Figure 2 1 Typical capsule anchor system [Reprinted with permission, from Cook, R.A., Kunz, J., Fuchs, W., and Konz, R.C. (1998). Behavior and Design of Single Adhesive Anchors Under Tensile Load in Uncracked Co ncrete. ACI Structural Journal 95(1), pp. 926. ] Figure 2 2 Typical injection anchor system [Reprinted with permission, from Cook, R.A., Kunz, J., Fuchs, W., and Konz, R.C. (1998). Behavior and Desig n of Single Adhesive Anchors Under Tensile Load in Uncracked Concrete. ACI Structural Journal 95(1), pp. 926. ] Figure 2 3 Various relationships of bond strength as a function of concrete strength [Reprinted, with permission, from Cook, R.A. and Konz, R.C. (2001). Factors Influencing Bond Strength of Adhesive Anchors. ACI Structural Journal 98(1), pp. 7686. ]

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141 A B Figure 2 4 Typical crack location of bonded anchor A) T op view. B) Section view. Figure 2 5 Sample bond strength versus temperature curve for three hypothetical adhesives [Reprinted with permission, from Cook, R.A., Kunz, J., Fuchs, W., and Konz, R.C. (1998). Behavior and Design of Single Adhesive Anchors Under Tensile Load in Uncracked Concrete. ACI Structural Journal 95(1), pp. 926. ]

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142 Figure 2 6 Extrapolation of sustaine d load displacements per ASTM E 1512 [Reprinted with permission, from Eligehausen, R. and Silva, J. (2008). The Assessment and Design of Adhesive Anchors in Concrete for Sustained Loading, < http://www.us.hilti.com/fstore/holus/techlib/docs/technical%20publications/an choring/hiltiadhesivesustainedloading.pdf> (Jun. 11, 2012). ] Figure 2 7 Basic pass/fail criteria per ICC ES AC58 Duration of load t [hours]Displacement [mm] 2000 600 days 1000 4000 1000 Duration of load t [hours] 2 1 2Displacement [mm]Detail A Detail A data points used for extrapolation log function extrapolation 600 Duration of load t [hours]Displacement [mm] 2000 600 days 1000 4000 1000 Duration of load t [hours] 2 1 2Displacement [mm]Detail A Detail A data points used for extrapolation log function extrapolation 600 LoadDisplacement 0110 creep u Displacement0creep Time LoadDisplacementNu75u110Static Tension Test @ 75o F Static Tension Test @ 110o F Creep Test Series @ 40% Nu75and 110o Fu75Nu110 600 days LoadDisplacement 0110 creep u Displacement0creep Time LoadDisplacementNu75u110Static Tension Test @ 75o F Static Tension Test @ 110o F Creep Test Series @ 40% Nu75and 110o Fu75Nu110 600 days

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143 Figure 2 8 Evaluation of load at Nadh [Reprinted, with permission, from ACI 355.411 (2011b). Qualification of Post Installed Adhesive Anchors American Concrete International, Farmington Hills, MI. ] Figure 2 9 Evaluation of load at Nadh [Reprinted, with permission, from ACI 355.411 (2011b). Qualification of Post Installed Adhesive Anchors American Concrete International, Farmington Hills, MI. ] lim lim lim lim lim

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144 Figure 2 10. Evaluation of load at Nadh [Reprinted with permission from ACI 355.4 11 (2011b). Qualification of Post Installed Adhesive Anchors American Concrete International, Farmington Hills, MI. ] Figure 2 11. Evaluation of load at Nadh [Reprinted with permission from ACI 355.4 11 (2011b). Qualification of Post Installed Adhesive Anchors American Concrete International, Farmington Hills, MI. ] lim lim lim lim lim lim

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145 Figure 2 12. Procedure for verifying the effectiveness of overhead adhesive injection [Reprinted, with permission, from ACI 355.411 (2011b). Qualification of Post Installed Adhesive Anchors American Concrete International, Farmington Hills, MI. ] Figure 2 13. Punch test apparatus [Reprinted with permission from ACI 355.4 11 (2011b). Qualification of Post Installed Adhesive Anchors American Concrete International, Farmington Hills, MI. ]

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146 Figure 2 14. Load v ersu s displacement and time v ersu s displacement graph for a sample anchor with incremental loading Figure 2 15. Sample stress versus time to failure graph

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147 Figure 2 16. Sample master curve using timetemperature superposition [Reprinted with permission, from Hunston, D. and Chin, J. (2008). Characterization of Ambient Cure Epoxies used in the "Big Dig" Ceiling Collapse, seminar for Virginia Tech Macromolecular Science and Engineering Department, Nov. 5, 2008. ] Figure 2 17. Individual compliance curves used in timestress superposition [Reprinted, with permission, from Jazouli, S., Luo, W., Bremand, F., VuKhanh, T. (2005). Application of Timestress Equivalence to Nonlinear Creep of Polycarbonate, Polymer Testing. Polymer Testing, 24, pp. 463467. ]

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148 Figure 2 18. Sample master curve using timestress superposition [Reprinted, with permission from Jazouli, S., Luo, W., Bremand, F., Vu Khanh, T. (2005). Application of Time stress Equivalence to Nonlinear Creep of Polycarbonate, Polymer Testing. Polymer Testing, 24, pp. 463467.] Figure 2 19. E' and E" master curves for an epoxy [Reprinted, with permission from Chin, J., Hunston, D., and Forster, A. (2007). ThermoViscoelastic Analysis of Ambient Cure Epoxy Adhesives used in Construction Applications NISTIR 7429, National Institute of Standards and Technology, Washington, DC.]

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149 Figure 2 20. tan delta master curve for an epoxy [Reprinted, with permission from Chin, J., Hunston, D., and Forster, A. (2007). ThermoViscoelastic Analysis of Ambient Cure Epoxy Adhesives used in Construction Applications NISTIR 7429, National Institute of Standards and Technology, Washington, DC.] Figure 2 21. Creep compliance curve for two epoxies [Reprinted with permission, from Chin, J., Hunston, D., and Forster, A. (2007). ThermoViscoelastic Analysis of Ambient Cure Epoxy Adhesives used in Construction Applications NISTIR 7429, National Institute of Standards and Technology, Washington, DC.]

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150 Figure 2 22. ASTM D638 Type I and Type II specimens [ Reprinted, with permission, from ASTM D638 08 Standard Test Method for Tensile Properties of Plastics copyright ASTM International, 100 Barr Harbor Drive, West Conshohocken, PA, 19428 ]

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151 A B C D E Figure 2 23 ACI 318 11 tension failure modes A) Steel strength failure. B) Concrete breakout f ailure. C) Pullout failure. D) Concre te sideface blowout failure. E) A dhesive bond strength failure. [Reprinted with permission, from ACI 318 11 (2011a). Building Code Requirements for Structural Concrete, American Concrete Institute, Farmington Hills, MI. ]

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152 A C B Figure 2 24 ACI 318 11 shear failure modes A) Steel st rength failure. B ) Concrete breakout failures. C) Concrete pry out failure. [Reprinted, with permission, from ACI 318 11 (2011a). Building Code Requirements for Structural Concrete, American Concrete Institute, Farmington Hills, MI. ]

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153 CHAPTER 3 TESTING PROGRAM This chapter summarizes the laboratory testing program used to investigate the effect of various parameters on the sustained load performance of adhesive anchors in concrete, the potential for using adhesive alone testing to evaluate the sustained load per formance of adhesive anchors, and the effect of early age concrete on the short term bond strength of adhesive anchors. The parameters considered as well as the triage approach used to prioritize the parameters are also presented. Parameters Identified fo r Testing C hapter 2 identified many parameters that have the possibility of affecting the performance of adhesive anchor systems. Because of the project budget and timeline, all parameters could not be tested; therefore a triage was conducted based on lit erature and the experience of the research team to determine which parameters were believed to have the potential for the most significant impact on sustained load performance and to develop a test program to investigate those parameters. This triage appr oach established three categories: High priority parameters. Parameters thought to have the potential for a significant impact on sustained load performance and definitely should be tested. Medium priority parameters. Parameters thought to have some potential for impact on sustained load performance and should be tested if budget and time permit. Low priority parameters. Parameters thought to have a minimal potential for impact on sustained load performance and are not recommended to be tested under this project. Table 3 1 lists the parameters identified earlier with their rated priority and test series identification as listed in the test matrices shown in Table 3 2 and Table 3 3 As noted in Table 3 1 all high and medium priority parameters were included in the

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154 planned test program. The following describes the rational e for the prioritization of the parameters listed in Table 3 1 and how the influence of each parameter would be evaluated if chosen for testing. High Priority Parameters These parameters were identified as having a strong possibility for affecting the sustained load performance of adhesive anchors. Elevated i n service t emperature. In service temperature has a significant effect on the sustained load performance of adhesive anchor systems especially for adhesives with different glass transition temperatures. Test series 3 and 4 tested at 120F and at 70F respectively in order to investigate the effect of in service temperature. Sustained load tests were performed with the bonded anchor system that showed the lowest glass transition temperature. These test series were intended to investigate if the relationship between long term bond strength and short term bond strength was influenced by the in service temperatures of 70F, 110F (baseline), and 120F. Moisture in s ervice. Test series 8 consisted of sustained load tests on an adhesive installed dry but maintained wet during the sustained load test. It was thought that the mechanisms that could potentially reduce the sustained load capacity due to inservice moisture were (1) plasticization of the adhesive, (2) reduction in the adhesive bond strength due to moisture, and (3) degr adation of the adhesive due to a high alkaline environment found in moist concrete. It was thought that exposure to a high alkaline environment was the controlling mechanism therefore sustained load tests were conducted on the adhesive that showed the hig hest sensitivity to alkalinity as determined by the resistance to alkalinity test results provided in the ICC ES AC308 Evaluation Service Report (ESR) for each adhesive.

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155 Type of a dhesive. It is well known that adhesives perform significantly different for given parameters and duration of loading. Three adhesives from different manufacturers and of different adhesive types were tested in this project. It was recommended to include at least an epoxy and a vinyl ester. Baseline short term and sustained load tests were conducted on all adhesives (series 1, 2, and 21). Due to project budget and timeline, sustained load tests were not conducted on all adhesives for every identified parameter, but rather the adhesive that was the most sensitive to the given parameter in short term tests. The three adhesives chosen were all ICC ES AC308 approved adhesive anchor products indicating that they are viable for structural applications. In addition, the test results of the extensive ICC ES AC308 testing program provided useful information in this research project. Adhesive c uring t ime w hen f irst l oaded. If a sustained load is applied before the adhesive is completely cured, the initial displacement and strain rate might be higher than that of a specimen with a c ompletely cured adhesive. In order to investigate the sensitivity to cure time, tensile creep adhesive alone tests (test series 22) were conducted on adhesive dogbone coupons at different degrees of cure time. Baseline short term tensile creep tests were conducted at the manufacturers specified cure time and at seven days. Sustained load tensile creep tests were conducted on all adhesives at seven days cure time and at the manufacturers specified cure time on the adhesive that showed the most sensitivi ty to cure time from the short term tests.

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156 Adhesive anchor pullout tests were not conducted on specimens at different cure times due to the logistical difficulties and the duration required to condition a specimen of concrete from the installation temperat ure to the testing temperature. Hole o rientation. The presence of voids has a significant effect on the bond stress of an adhesive anchor. It is well known that voids in the adhesive will occur more often with anchors improperly installed horizontally or overhead. Anchors were installed horizontally and vertically in test series 5 and 6 respectively Sustained load tests were performed on one bonded anchor system Hole d rilling. Hole drilling method has been shown to influence bond strength due to the resulting roughness of the sides of the holes. Most manufacturers recommend rotary hammer drills with carbide bits. While in general, holes were drilled by rotary hammer drills with carbide drill bits, test series 13 used a diamond core drill. The susta ined load tests were performed with the product approved for core drilling that was shown to be the most sensitive to the type of drilling with respect to bond strength established by short term tests. Hole c leaning. It is well known that the degree of hole cleaning can significantly influence the short term bond strength. Test series 9 used a reduced cleaning effort (50% of the manufacturers recommended cleaning procedure as specified by ACI 355.411 7.5) on anchors installed in dry holes. The sustained load tests were performed with the product that was shown to be the most sensitive to a reduced cleaning effort with respect to bond strength established by short term tests. Moisture in i nstallation. Due to the significant decrease in short term bond strength for anchors installed in damp and submerged holes, it was recommended that

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157 the influence of moisture during installation be tested in this project. Test series 7 installed anchors in a wet/damp hole and conduct ed sustained load tests in a dry con dition. The sustained load tests were performed with the product that was shown to be the most sensitive to a wet installation with respect to bond strength established by short term tests. Type of c oncrete. Anchor pullout tests at the University of Flor ida have shown that the short term bond strength might be influenced by the composition of the concrete (e.g. amount of fly ash or blast furnace slag). The reasons for this might be due to the different porosity of the concrete compared to concrete without additives or perhaps due to the general surface condition of the drilled/cleaned hole. Test series 12 (standard DOT mix), 14 (20% fly ash), and 15 (50% blast furnace slag) were introduced in an attempt to address this question. The sustained load tests were performed with the product that was shown to be the most sensitive to the different concrete mixes. Medium Priority Parameters These parameters were identified as having a possibility for affecting the sustained load performance of adhesive anchors a nd/or they were recommended by the NCHRP panel for investigation during the proposal review. Installation t emperature. If anchors are installed at low temperatures the final degree of curing is lower compared to installation at normal temperature. This m ight result in a reduction of the long term bond strength. Therefore test series 10 and 11 were performed with anchors installed in concrete at the manufacturers lowest permissible installation temperature with the adhesive preheated to the manufacturer s lowest permissible adhesive temperature to ease adhesive injection. The adhesive with the lowest degree of crosslinking was chosen for testing. As any additional heating

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158 after installation causes additional curing of the adhesive, test series 10 was conducted at the manufacturers minimum temperature and test series 11 was conducted at 110F (43C). Un confined t est s etup. Confined tests are used to ensure a bond failure for bond strength analysis The bond failure may occur at the interface between the anchor and the adhesive and/or the adhesive and concrete and/or in the adhesive itself. In contrast, in unconfined tests, failure is often characterized with a concrete cone for concrete breakout failure or a combination of a shallow concrete cone and bond failure In order to ensure that both the short term tests and sustained load tests in this program resulted in failures associated with bond strength, the confined testing method was used. Final design standards are currently based on unconfined bond strength established from short term confined tests modified by a factor of 0.75 per ACI 355.411. In general, it is assumed that the ratio of long term bond strength to short term bond strength is independent of the type of support (confined, unconfined) provided bond failure controls in the unconfined condition and not concrete breakout. To check the validity of this assumption unconfined tests were performed (test series 16). Early age c oncrete. It was suggested by the NCHRP panel to investigate th e effects of concrete age on the short term bond strength. It is assumed that the synergistic effects of the low concrete strength and the high moisture content found in early age concrete can affect the short term bond strength of an anchor installe d in early age concrete. Test series 17 investigated the effects of concrete age by installing anchors in concrete at various ages (3, 6, 13, 20, and 27 days) and conducting short

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159 term anchor pullout tests after 24 hours of adhesive cure time. Sustained load performance due to installation in early age concrete was not to be investigated in this project. Low Priority Parameters These parameters were identified as possibly having a minimal effect on the sustained load performance of adhesive anchors or not at all. It was decided by the researchers and the NCHRP panel that they not be tested during this project. Reduced i n service t emperature. During approval tests of bonded anchors according to ICC ES AC308 or EOTA (2002) freeze/thaw tests are performed with anchors installed at normal ambient temperature in wet concrete. The anchors are loaded in tension with 55% the mean short term load. After 50 freeze/thaw cycles the residual bond strength is measured which must be statistically equivalent with the short term bond strength. It was recommended that the influence of long term below freezing temperatures on the long term bond strength be considered low priority and not be investigated during the present research project. Freeze t haw. See discussion above r egarding reduced inservice temperature. It was recommended that influence of freezethaw cycling be considered a low priority and not be investigated in this research project. Mixing e ffort. The test program used bonded anchors with the adhesive deliver ed in cartridges. The anchors were installed according to the MPII. When using cartridges with their corresponding mixing nozzle and the correct injection gun and following the manufacturers instructions (typically discarding the first inches of the mix ed mortar) it may be assumed that the adhesive is thoroughly mixed. Incorrect mixing of the adhesive may only occur with these systems if the mixing nozzle is

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160 manipulated (e.g. shortened) or an inappropriate mixing gun is used. These are gross installation errors outside of the MPII and were not recommended to be evaluated in this research project. Incomplete mixing might occur with bonded anchors if the adhesive is delivered in bulk and mixed on site in an open container without controlled metering with a hand or machine mixer. These types of bonded injection anchors are not currently addressed in this research project since they are outside of the scope of ICC ES AC308 (.2.4.2) and ACI 355.411 (1.2.3). Bond l ine t hickness. In general, all tests wer e performed with the gap thickness according to the MPII. A test series was proposed for consideration where the diameter of the hole was enlarged to check if the ratio of long term bond strength to short term bond strength was influenced by the hole diam eter. The researchers and the NCHRP panel chose to not test this parameter as it was deemed a gross installation error and to allow for testing of other higher priority parameters. Fiber c ontent of a dhesive. Since bulk mixing products were not considered by this project, the influence on sustained load performance of fiber content as modified by the installer was not addressed either. The influence of fiber content on sustained load performance could have coincidentally been examined if two of the three adhesives chosen were identical except for the amount of fiber content. However, this was not the case and the influence of fiber content was not a criterion when choosing the three adhesives to test in the project. Chemical r esistance. Chemical resistance is currently tested by ACI 355.411 .8 by two durability tests, a test for alkalinity and an optional sulfur dioxide test. As

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161 discussed earlier, both of these tests subject 13/16 slices to very harsh environments for long durations (2000 hours). T est series 8 which tests for sensitivity to inservice moisture will subject the adhesive anchor to an alkaline environment since damp concrete is a naturally alkaline material. Since adhesive anchors installed in concrete are embedded much deeper than the 13/16 slices used in ACI 355.411 durability tests, the exposure to sulfur dioxide of a normal adhesive anchor will not be as extreme as the condition found in the tests. Sustained load adhesive anchor chemical resistance tests were not conducted since the durability tests of ACI 355.411 are long term tests and the reduction factor obtained from these tests, dur, was considered sufficient to account for chemical effects for both short term and sustained loading conditions. Depth of h ole ( e mbedment d epth). Extensive short term testing and analytical work has shown that the bond strength is not significantly influenced by the embedment depth in the ranges typically specified of about four to 20 anchor diameters. The author feel s that it can be safely assumed that the long term bond strength is also not significantly influenced by the embedment depth. Therefore, all tests were performed with one embedm ent depth per anchor diameter. Anchor d iameter. For most bonded anchor systems the bond strength measured in short term tests decreases somewhat with increasing anchor diameter (Eligehausen et al. (2006b)). The NCHRP panel initially requested anchor diameter be investigated, but later agreed to forgo this test parameter in order to evaluate a standard D OT concrete mix (test series 12).

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162 Concrete s trength. As discussed earlier, there is no direct correlation between concrete strength and bond strength. Since confined tests isolate the failure mode to the adhesive bond the effect of the concrete strength was not considered to be significant. As a result, influence of concrete strength on sustained load performance of adhesive anchors was not included in this test program. Type of c oarse a ggregate. This was not directly tested in this test program ( test series 12 used granite aggregate but the concrete mix was different from the control in many ways) however the effects of aggregates are accounted for in the ACI 355.411 test program via a series of Round Robin tests which evaluate the impact of regional d ifferences on concrete mixtures. Cracked or u ncracked c oncrete. Cracked concrete was not tested in this test program, but the ACI 355.411 test program contains test procedures for anchors to be qualified for use in both cracked and uncracked concrete. Anchor Pullout Testing Program Based on the triage approach discussed earlier, Table 3 2 presents the test matrix for anchor pullout testing program of threaded rods embedded in concrete for test series 1 17. Table 3 2 shows the test series, testing conditions with the tested parameter, explanations in notes at the bottom, number of test per series, and location of testing. Tests were conducted at the University of Florida (UF) and the University of Stuttgart (US). Tes t series 1 16 began with short term load tests per the short term te nsion test procedure per ASTM E 488. Five repetitions were conducted on each adhesive and their values averaged to determine the mean short term load strength.

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163 Test series 1 16 concluded with a series of sustained load tests per the test procedure per AASHTO (2010c) TP 84 10 with a few modifications. Three anchors were loaded until failure at four stress levels for test series 1 and 2 and three stress levels for test series 316. The time to failure was evaluated at the time of rupture and as the time to tertiary creep per AASHTO (2010c) TP 84 10. For laboratory logistics and in order to remove the effects of continued curing beyond the manufacturers stated cure time, all anchors were allowed to cure seven days, and then were conditioned to the testing temperature for 24 hours prior to testing. Test series 17 only evaluated the effect of early age concrete on the short term bond strength. Its influence on the sustained load performanc e was not evaluated in this research project and therefore no sustained load tests were conducted for test series 17. Adhesive Alone Testing Program Based on the triage approach discussed above, Table 3 3 presents the test matrix for the tensile creep testing program of dogbone specimens of the adhesives for series 21 and 22. Test series 21 22 began with short term load tests per the tensile testing procedure presented in ASTM D638. Five repetitions were conducted on each adhesive and their values averaged to determine the mean short term load strength. Test series 21 22 concluded with a series of sustained load tests per the tensile creep test procedure from AST M D2990. Three adhesive dogbone specimens were loaded until failure at four stress levels for test series 21 and 22. The timeto failure was determined as time to rupture as discussed above.

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164 Adhesive alone tests were conducted on a Dynamic Shear Rheometer (DSR) to develop master curves using timetemperature and timestress superposition to compare with creep compliance curves from dogbone and anchor pullout tests. Early Age Concrete Testing Program The same three adhesives used in this project were insta lled in concrete of various ages (3, 6, 13, 20, and 27 days after casting). Short term load tests per the short term te nsion test procedure per ASTM E 488 were conducted 24 hours after installation. Five repetitions were conducted on each adhesive and their values averaged to determine the mean short term load strength. Various environmental and material properties were evaluated for influence. The proper ties identified for evaluation were: Concrete compressive strength Concrete split tensile strength Amb ient and internal concrete temperature Ambient and internal concrete humidity Initial surface absorption of the concrete surface and sides of hole Concrete hardness by rebound and indention hammers Bore hole roughness Summary This chapter summarized the parameters that could possibly affect sustained load performance of adhesive anchor systems. Due to project budget and timeline, a triage was conducted to prioritize the parameters in order to test those thought to have the mos t impact. C hapter 4 presents the details on how this testing program was conducted.

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165 Table 3 1 Prioritization of i dentified p arameters Parameter High p riority Medium p riority Low p riority Test s eries* In s ervice f actors Elevated t emperature X 3,4 Reduced t emperature X Moisture in s ervice X 8 Freeze t haw X Factors r elated to the a dhesive Type of a dhesive X 1,2,21 Mixing e ffort X Adhesive c uring t ime w hen f irst l oaded X 22 Bond l ine t hickness X Fiber c ontent of a dhesive X Chemical r esistance X Installation f actors Hole o rientation X 5,6 Hole d rilling X 13 Hole c leaning X 9 Moisture in i nstallation X 7 Installation t emperature X 10,11 Depth of h ole ( e mbedment d epth) X Anchor d iameter X Type of c oncrete X 12,14,15 Concrete s trength X Type of c oarse a ggregate X Cracked or u ncracked c oncrete X Confined or u n confined t est s etup X 16 Early age c oncrete X 17 See Table 3 2 for description of test series 1 17 and Table 3 3 for description of test series 21 22

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166 Table 3 2 Test matrix for anchor pullout testing Test s eries Test d escription (Influencing parameter) Installation t emperature Orientation during installation Moisture of concrete during installation/ service Cleaning Anchor (Size x hef) Concrete c omposition Product t ype A a Product t ype B a Product t ype C a Test t emp. Type of support Number of sustained load steps b Number of sustained load tests Number of reference tests Test Lab m 1 Baseline tests UF 75F downward dry/dry full 5/8x3 Standard X X X 110F confined 4 36 15 UF 2 Baseline tests US 75F downward dry/dry full M12x80 Standard X X X 110F confined 4 36 15 US 3 Service temperature 75F downward dry/dry full M12/80 Standard X c >120F confined 3 9 5 n US 4 Service temperature 75F downward dry/dry full M12/80 Standard X c 70F confined 3 9 5 n US 5 Installation direction 75F horizontal dry/dry full M12/80 Standard X d X d 110F confined 3 18 10 n US 6 Installation direction 75F overhead dry/dry full M12/80 Standard X d X d 110F confined 3 18 10 n US 7 Moisture during installation or service 75F downward damp/dry full 5/8x3 Standard X e 110F confined 3 9 5 n UF 8 Moisture during installation or service 75F downward dry/damp full M12/80 Standard X f 70F confined 3 9 5 n US 9 Hole cleaning 75F downward dry/dry reduced 5/8x3 Standard X g 110F confined 3 9 5 n UF 10 Installation temperature MFR min h i downward dry/dry full M12x80 Standard X j MFR min h confined 3 9 5 n US 11 Installation temperature MFR min h i downward dry/dry full M12x80 Standard X j 110F confined 3 9 5 n US 12 DOT c oncrete mix 75F downward dry/dry full 5/8x3 DOT X 110F confined 3 9 5 n UF 13 Type of drilling 75F downward dry/dry full 5/8x3 Standard X 110F confined 3 9 5 n UF 14 Concrete composition 75F downward dry/dry full 5/8x3 with FA X k 110F confined 3 9 5 n UF 15 Concrete composition 75F downward dry/dry full 5/8x3 with BFS X l 110F confined 3 9 5 n UF 16 Test set up (wide support) 75F downward dry/dry full 5/8x3 Standard X 110F un confined 3 9 5 n UF 17.04 Concrete a ge (tested at 4 days) 75F downward dry/dry full M12x80 Standard X X X 75F confined 0 0 1 5 n US 17.07 Concrete a ge (tested at 7 days) 75F downward dry/dry full M12x80 Standard X X X 75F confined 0 0 1 5 n US 17.14 Concrete a ge (tested at 14 days) 75F downward dry/dry full M12x80 Standard X X X 75F confined 0 0 1 5 n US 17.21 Concrete a ge (tested at 21 days) 75F downward dry/dry full M12x80 Standard X X X 75F confined 0 0 1 5 n US 17.28 Concrete a ge (tested at 28 days) 75F downward dry/dry full M12x80 Standard X X X 75F confined 0 0 1 5 n US Sum 216 185 Notes: a Type A = vinyl ester system, type B = epoxy system, type C = epoxy system b 4 sustained loads N p / N u,m (reference) 0.75/0.65/0.55/0.45. Creep tests with N p = 0.55 N u,m will be used to compare with current approach of AC308 3 sustained loads N p / N u,m (reference) 0.70/0.55/0.40 c Only the product that is most sensitive to increased temperature (high ratio glass transition temperature to service temperat ure) will be tested d Only the top two products that are most sensitive to installation direction (occurrence of voids) in short term tests will be tested e Only the product that is most sensitive to wet concrete in short term tests will be tested f Product that is sensitive to high alkalinity will be tested. The tests are performed at normal ambient temperature because u nder increased temperature the concrete will dry out. g Only the product that is most sensitive to hole cleaning (no brushing) will be tested h Concrete at manufacturer's lowest permissible concrete temperature i Mortar at manufacturer's lowest permissible mortar preheating temperature j Only the product that is most sensitive to low installation temperature (low degree of cross linking) will be tested k Only the product that is most sensitive fly ash concrete will be tested l Only the product that is most sensitive to blast furnace slag concrete will be tested m UF = University of Florida, US = University of Stuttgart n It is assumed that the influence of the investigated parameter on the short term bond strength is known from previous tests. If not all products will be tested and the number of reference tests will increase

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167 Table 3 3 Proposed Test Matrix for Tensile Creep Testing Short t erm t ests Sustained load t ests b Test s eries Test d escription Cure t ime Test t emp Product t ype A a Product t ype B a Product t ype C a Product t ype A a Product t ype B a Product t ype C a 21 Baseline 7 days 110F 5 5 5 12 12 12 22 Cure t ime mfr spec 110F 5 5 5 12 c Sum 10 10 10 24 12 12 Notes: a Type A = vinyl ester system, type B = epoxy system, type C = epoxy system b Four stress levels times three repetitions for baseline c Only the product that is most sensitive to load at reduced cure time will be tested

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168 CHAPTER 4 METHODS AND MATERIAL S This chapter presents the methods and materials used in the experimental program. The description of the anchor pullout tests at the University of Stuttgart and the adhesive alone t ests are presented in Appendix B and Appendix C as these were written primarily by other researchers in this study. Anchor Pullout Tests University Of Florida Overview The test series listed in Table 4 1 were conducted at the University of Florida; see Table 3 2 for a detailed test matrix. The short term (reference) and sustained load (creep) tests generally followed the test procedure found in AASHTO (2010c) TP 84 10 with the following modifications: Concrete AASHTO (21010c) TP 84 10 specifies that the concrete mix should be plain concrete without any admixtures. For all tests except for test series 12, 14 and 15 the concrete mix did not have any admixtures or additives. Test series 12 had granite aggregate, water reducer, and fly ash. Test series 14 and 15 used the baseline concrete mix but replaced the cement with 20% fly ash and 50% blast furnace slag respectively AASHTO (2010c) TP 84 10 specifies that the concrete mix should have a compressive strength between 2500 to 4000 psi at time of testing. For this project, the NCHRP panel chose to specify concrete with a compressive strength between 4000 and 6000 psi at time of testing to better conform to typical DOT concrete mixes. Adhesive Adhesives of different chemistries f rom three manufacturers were chosen to investigate their sensitivity to sustained load. Only ICCES AC308 qualified adhesive systems were used. The adhesive chemistries are briefly described below:

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169 Adhesive A: This product is a vinyl ester with acrylic monomers with a peroxide hardener and quartz filler Adhesive B: This product is an epoxy resin with amine hardeners and quartz filler Adhesive C: This product is an epoxy resin with an amine blend. Anchor As allowed in AASHTO (2010c) TP 84 10, a 5/8 diameter threaded rod was used to avoid a steel failure mode. As allowed in AASHTO (2010c) TP 84 10, to further reduce the possibility of steel failure, ASTM A354 grade BD steel with 130 ksi yield strength and 150 ksi ultimate strength was used which is greater t han the minimum specified strength of ASTM A193 grade B 7 steel. A 3 1/8 embedment depth for the 5/8 diameter bars was chosen based on minimum recommendations from AASHTO (2010c) TP 84 10 to ensure adhesive failure. Test p rocedure All tests were confined tests except for test series 16 which evaluated the effect of the test set up and were unconfined tests. The stress levels set for the sustained load (creep) test were initially at 85%, 75%, and 65% mean short term load for all test series and an addition al stress level of 55% mean short term load for the baseline tests. After testing began, it was decided to adjust the stress levels due to early failure times at 85% and 75% mean short term load. As allowed in AASHTO (2010c) TP 84 10 the frequency of data readings for the long term (creep) tests was reduced over time according to the following schedule: Every 0.5 seconds during loading Every 5 seconds for 10 minutes (120 readings) Every 30 seconds for 1 hour (120 readings) Every 5 minutes for 10 hours (120 readings) Every hour thereafter until failure

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170 Test A pparatus This section describes the test apparatus used for the short term (reference) and sustained load (creep) tests. For each case, the standard apparatus is described which was used in the majori ty of the test series and variations for specific test series are discussed later. Standard s hort t erm ( r eference) t est a pparatus The short term confined testing apparatus conformed to the requirements in ASTM E488. The testing apparatus for the short term (reference) test ( Figure 4 1 ) used a 6 x 6 x 0.03 thick Teflon PTFE (Polytetrafluoroethylene) confining sheet placed under an 8 x 8 x 5/8 thick steel confi ning plate. The confining sheet was used to correct for any surface irregularities in the concrete. A 11/4 hole was drilled though the center of the confining sheet and confining plate to fit around the anchor in accordance with ASTM E488. Two 3 x 5 x 1/4 rectangular steel tubes 8 long were placed parallel to each other on either side of the anchor. A 10 x 10 x 1 thick steel plate with a 23/4 diameter hole in the center was placed on the rectangular steel tubes to support an Enerpac model RC H 603 Holl O Cylinder 60 ton hydraulic ram. A Houston Scientific model 3500 100kip load cell was placed on top of the ram sandwiched between four 3 x 3 x 1/4 square plates (two above and two below) with a 11/8 diameter hole in the center. A washer and a nut were placed above the square plates. The 5/8 diameter anchor was fed through an 11/16 diameter hole in a nonrigid coupler and secured with a nut. The oversized hole in the coupler prevented bending forces from being transferred from the coupl ing rod to the anchor. A 1 diameter loading rod was threaded into a hole in the top of the coupler and passed through the ram and load cell and was secured at the top with a washer and two nuts.

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171 A 2 x 16 x steel flat bar was welded to the bottom of the coupler and BEI Duncan Electronics model 9610 linear motion position sensors (linear pots) were secured to each end of the flat bar equidistant from the center line of the anchor. The linear pots were oriented downwards and measured displacement between the flat bar and the surface of the concrete. The linear pots were oriented in this manner so that as the flat bar raised, the plunger extended, ensuring that the linear pot was not damaged if the anchor failed drastically. A 2 x 2 x steel basepl ate was placed on top of the concrete surface underneath each linear pot plunger to raise the initial bearing point of the plunger and to provide a smooth measuring surface. Test s eries 16 ( unconfined) s hort term t est a pparatus The short term unconfined testing apparatus conformed to the requirements in ASTM E488. The 6 x 6 x 0.03 thick Teflon PTFE (Polytetrafluoroethylene) confining sheet and the 8 x 8 x 5/8 thick steel confining plate were not used in this test series. The 3 x 5 x 1/4 rectangular steel tubes were placed parallel to each other on either side of the anchor no closer than two times the embedment depth. An 18 x 18 x 1 thick steel plate with a 23/4 diameter hole in the center was placed on the rectangular steel tubes to suppor t an Enerpac model RCH 603 Holl O Cylinder 60 ton hydraulic ram. Figure 4 2 shows the modifications to the short term (reference) test apparatus for test series 16. Standard sustained load (creep) test apparatus The sustained load confined testing apparatus conformed to the requirements in ASTM E488 and ASTM E1512. The testing apparatus for the sustained load (creep) test ( Figure 4 3 ) used the same Teflon PTFE (Polytetrafluoroethylene) confining sheet and steel confining plate as in the short term load test apparatus. Existing steel frames

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172 from previous sustaine d load tests conducted at the University of Florida by Cook et al. (1996) were used to contain compression springs to apply the sustained load. Springs were chosen instead of a hydraulic ram for these sustained load tests in order to reduce the chance of loss of load caused by a hydraulic leak. The springs used were provided by the Florida Department of Transportation (FDOT) State Materials Office in Gainesville, Florida. Two sets of steel wire springs (large and small) were used individually or in parall el. The large springs were approximately 5.5 in diameter by 8 in uncompressed height and had an average approximate spring stiffness of 10.2 kips/in and a working load range up to 16 kips. The small springs were approximately 3 in diameter by 8 in uncompressed heights and had an average spring stiffness of 3.2 kips/in and a working load range up to 5 kips. For loads up to 15 kips, the large springs were used individually, for loads between 15 kips and 21 kips the large and small springs were used in parallel with an average combined spring stiffness of 13.4 kips/in. The 5/8 diameter anchor was connected to the 1 diameter loading rod by means of the same non rigid coupler as in the short term load test apparatus. Linear pots were used to measure displacement in the same configuration as in the short term load test apparatus. A hydraulic jack chair of four parallel Central Hydraulics model 95979 20 kip rams with a 7/16 throw was used to smoot hly and quickly apply the sustained load to the anchor. During loading, a load cell on top of the hydraulic jack chair measured the transfer of force from the spring to the anchor. Once the desired load was achieved, a nut was tightened on top of the spr ing below the hydraulic jack chair and the pressure in

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173 the rams was released. The use of the hydraulic jack chair allowed for one load cell to be used for all tests. A test frame with the hydraulic jack chair is shown in Figure 4 4 To prevent the test apparatus from falling over due to the dynamic load on the frame caused by an anchor pullout, the test frames were secured to the concrete blocks with loading straps. T est series 16 ( unconfined) sustained load test apparatus The sustained load unconfined testing apparatus conformed to the requirements in ASTM E488 and ASTM E1512. The 6 x 6 x 0.03 thick Teflon PTFE (Polytetrafluoroethylene) confining sheet and the 8 x 8 x 5/8 thick steel confining plate were not used in this test series. The 3 x 5 x 1/4 rectangular steel tubes were placed parallel to each other on either side of the anchor no closer than two times the embedment depth. An 18 x 18 x 1 thick s teel plate with a 23/4 diameter hole in the center was placed on the rectangular steel tubes to support the load frame. Figure 4 5 shows the modifications to the sustained load (creep) test apparatus for test series 16. Specimen P reparation The test specimens consisted of three parts; the concrete test member, the adhesive, and the anchor rod. Concrete test member The concrete test members for the short term (referen ce) tests were poured in 60 x 16 x 12 forms. Minimal reinforcement of two #3 60 ksi steel reinforcing bars were placed longitudinally 5 from the bottom of the slab. Four diameter PVC pipes were placed at midheight which allowed for diameter rods to later be passed through the concrete test member in order to accommodate handling.

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174 The concrete test members for the sustained load (creep) tests were poured in 16 x 16 x 12 forms. No reinforcement was provided. Two diameter PVC pipes were pl aced at midheight in order to accommodate handling. All the forms used in this project were made of high density overlay plywood and were assembled with threaded rod and wing nuts which allowed for multiple uses due to the large number of test members req uired. Since only twenty sustained load tests could be conducted simultaneously, the production of the concrete test specimens ( Figure 4 6 ) was staggered in ten separ ate pours denoted as concrete series A J. The pour dates and number of test blocks produced in each series are listed in Table 4 2 In order to provide a smooth testing surface the blocks were cast upside down against the high density overlay plywood. After the first pour, it was decided to place a 1/8 thick sheet of Teflon PTFE (Polytetrafluoroethylene) at the bottom of the form to provide an even smoother sur face and ensure against a lesser quality surface in the later pours. The concrete for mixes A I was batched, mixed, and placed at the Florida Department of Transportation (FDOT) State Materials office in Gainesville, FL. Concrete with round river gravel without any admixtures (except for series H and I which included 20% fly ash and 50% blast furnace slag respectively ) was specified with a mean compressive strength between 4000 and 6000 psi during testing. All of the materials were batched by weight. M oisture samples were taken of the coarse aggregate (#7 and #89 stone) and allowed to dry in one of two Blue M large ovens ( Figure 4 7 ) at 230F for 24 hours in order t o determine the percent moisture. The sand was oven dried in the same ovens at 230F for 24 hours. Concrete was mixed in a

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175 Lancaster 27 CF counter current batch concrete mixer ( Figure 4 8 ) and discharged into a large hopper and then placed into the forms with shovels and vibrated with an electric vibrator. Due to the size of the concrete mixer and forms, the concrete for each series was made in three batches. Plas tic properties (slump, percent air, temperature, and unit weight) were evaluated and 4 x 8 cylinders were made for each batch of every series. The concrete for mix J was batched and mixed by Florida Rock Industries, a local ready mix plant and placed at the University of Florida (UF) Structures Laboratory in Gainesville, FL. Mix J was designed by the NCHRP panel and included granite aggregate, water reducer, fly ash, and air entrainment. The mix designs and plastic properties for concrete series A J ar e included in Appendix A Following the pour, the concrete was covered with plastic for 24 hours. After the first 24 hours, the concrete was covered with wet tarps and plastic and maintained wet for five days. The cylinders were capped with plastic lids. After six days the forms were removed and the cylinders demolded. The concrete test members and cylinders were maintained in the UF structures laboratory thereafter. Concrete compressive strength was determined by testing the cylinders in general accor dance with ASTM C39 on a Test Mark model CM 5000DG compression machine ( Figure 4 9 ) calibrated in August 2009 and August 2010 located at the FDOT State Materials Offi ce in Gainesville, FL. The cylinders were ground smooth on a Hi Kenma cylinder grinding machine ( Figure 4 10) prior to testing. A concrete strengthage relationship was determined for each series by testing 4 x 8 cylinders at 7, 14, 28, 56,

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176 112, 224, and 448 days or at the end of testing for that series whichever came first. The average compressive strength for each series is presented in Tabl e 4 3 Adhesive The three adhesive products were stored in an environmentally controlled room maintained within the temperature and humidity range specified by the manufacturers prior to installati on. An chor rods The anchor rods were ASTM A354 grade BD 5/8 diameter 11 threads per inch (UNC) steel threaded rod fabricated by Glaser & Associates from Martinez, CA and American Supply Company of Jackson MS This grade of steel ha d a specified yield str ength of 130 ksi and a specified tensile strength of 150 ksi. The anchor rods were cut to a length of 5.75 and their ends ground and chamfered with a bench grinder and steel brush to remove burrs and to clean up the threads in order to install the nuts. The anchors were stored in a sealed bucket in oil soaked shredded paper to prevent rusting. Prior to installation, the rods were cleaned with acetone, allowed to air dry, and protected with paper until installed. Instrumentation Measurement Displacement. Direct measurement of the anchor displacement was not possible due to the location of the test apparatus. Therefore, a 16 x 2 x ASTM A36 steel flat bar was attached to the bottom of the nonrigid coupler that connected the anchor to the 1 diameter loading rod ( Figure 4 1 Figure 4 5 ). Two BEI Duncan Electronics model 961 0 linear motion position sensors (linear pots) were fixed to this flat bar, one on each

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177 end, equidistant from the centerline of the anchor. The displacement was calculated as the average of the two linear pot measurements. Load. The tension in the anchor was measured indirectly as a compressive reaction of either the hydraulic ram or the compression spring in the test apparatus. For the short term (reference) tests, the load was measured by a Houston Scientific model 3500 100kip load cell excited by a 10VDC amplifier with a gain of 500. For the sustained load (creep) tests, the loads were measured by the same Houston Scientific load cell during loading. Once the load was applied to the anchor, the load cell was removed and the load was monitored by the spring stiffness and displacement. Temperature. Temperature in each concrete test slab was measured by National Semiconductor LM35 Precision Centigrade Temperature Sensors. The temperature sensors were located 2 inches deep in the top of the concrete test specimen placed in 1/2 diameter holes drilled just prior to conditioning and sealed with rubber grommets to allow for reuse. Ambient air temperature in the test chamber was measured by a Cincinnati SubZero EZT 560i Environmental Chamber Controller in stalled in the Cincinnati SubZero Model WM STH 11522 H/AC Walk In Stability Chamber. Analog cards installed in the Cincinnati SubZero EZT 560i Environmental Chamber controller provided an analog signal output allowing the ambient air temperature to be monitored by the data acquisition system. Humidity. Relative humidity in the test chamber was measured by a Cincinnati Sub Zero EZT 560i Environmental Chamber Controller installed in the Cincinnati SubZero Model WM STH 11522 H/AC Walk In Stability Chamber. Analog cards installed in the Cincinnati Sub Zero EZT 560i Environmental Chamber controller provided an

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178 analog signal output allowing the humidity to be monitored by the data acquisition system. Time. Time was measured using the computers internal clock. Instrument calibration Displacement. The linear motion position sensors were calibrated against a Fowler digital caliper over their full range of 1 at 1/8 increments. The measurements were adjust ed for variations in power supply voltage and normalized to a 10 volt power supply. Load. The Houston Scientific model 3500 100kip load cell was calibrated in July 2010 at the Florida Department of Transportation State Materials Office in Gainesville, FL on a Test Mark model CM 5000DG compression machine. The load cell was calibrated over a range of 0 to 80 kips with nine data points. The compression springs were calibrated in June 2010 on an INSTRON System 3384 150 kN universal testing machine to determine their stiffness and working load. The large springs were calibrated individually over a range of 0 to 15 kips with about 500 data points. For loads above 15 kips, the large and small springs were calibrated in parallel over a range of 0 to 20 kips with about 630 data points. Temperature. The National Semiconductor LM35 Precision Centigrade Temperature Sensors factory calibration was validated in June 2010 against a high quality mercury thermometer over a temperature range of 100F to 120F. The te mperature sensor in the test chamber was calibrated by the factory. Humidity. The humidity sensor in the test chamber was calibrated by the factory.

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179 Environmental C ontrol Standard t emperature An air conditioned space was used to store and condition the adhesive at 75F 10F and 50% 10% relative humidity. When conditions allowed, the test slabs were stored prior to installation and testing on the shop floor of the UF Structures Laboratory at 75F 10F and 50% 10% relative humidity. Elevated t emperature A 12 by 12 by 8 tall Cincinnati SubZero Model # WM STH 11522 H/AC Walk In Stability Chamber ( Figure 4 11 ) was used to condition and test at the elevated testing t emperature of 110F +10F/ 0F and below 40% relative humidity for the short term (reference) and sustained load (creep) test. The chamber had a temperature range of 20C to 60C ( 4F to 140F) and a relative humidity range of 10% to 95%. The chamber w as equipped with a CSZ EZT 560i Touch Screen Controller to monitor and control the temperature and humidity. The concrete test specimens were placed on furniture dollies in order to facilitate test rotation and to raise them off the ground by a few inches to promote better air flow and a uniform temperature within the concrete. The stability chamber was able to simultaneously house 20 sustained load anchor pull out test specimens and one short term anchor pull out test specimen on the floor. Shelves were built along the walls to house the 16 adhesive only test frames. Figure 4 12 and Figure 4 13 show the testing chamber with 20 sustained load tests running (2 not visible). A short term testing slab is in the foreground. Figure 4 14 shows the layout of the anchor pull out test speci mens in the stability chamber.

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180 Data M anagement and A cquisition During the testing and conditioning of the test slabs to the elevated temperature, a Microsoft compatible computer ran several National Instr uments L ab VIEW 8.6 software programs developed by the author to collect, record, and display the data. Measured values included load, displacement, temperature, humidity, and time. Data acquisition was performed with a National Instruments NI cDAQ 9172 chassis with several National Instruments NI 9205 modules to interface with the instrumentation. Due to minor fluctuations in the ten volt power supply, the LabVIEW programs recorded the power supply voltage with each data reading and the position readings were appropriately adjusted to a normalized ten volt power supply. Data sampling program A LabVIEW 8.6 program ( Figure 4 15) was developed to centrally sample data for every test. This program provided a half second time averaged record sampled at 2000 Hz. Global variables for each of the twenty sustained load test frames and the one short term test frame were updated every half second to the computer memory to be read when needed by the separate LabVIEW programs for each test frame. Each global variable included a timestamp, and the voltage readings for the two linear pots, power supply, load cell, concrete temperature sensor, and environmental chamber temperatur e and humidity. Short term (reference) test program A LabVIEW 8.6 program ( Figure 4 16 & Figure 4 17) developed for this project was used for the short term (reference) tests. Load, displ acement, temperature, and humidity readings were recorded at half second intervals. A load versus displacement curve was displayed on the screen for real time feedback. Load rate control was

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181 monitored by plotting the actual load rate from the hydraulic h and pump against an ideal load rate to cause bond failure of the expected load in 120 seconds on a load versus time graph. This real time plot was used to assist the pump operator in applying a constant load rate. The latest data readings were displayed on the screen and each data reading was automatically recorded in a Microsoft Excel spreadsheet. Long term (creep) test program A LabVIEW 8.6 program ( Figure 4 18 to Figure 4 20) developed for this project was used for the sustained load (creep) test. Load, displacement, temperature, and humidity readings were recorded at progressively longer intervals over the course of the test as discussed previously. If it became necessary to apply additional load to the anchor during the test, the program entered a tightening phase in which data was recorded every half second. Once tightening was completed, the program began sampling every five seconds and proceeded through the above sampling schedule. A displacement versus time curve ( Figure 4 19) for each anchor and a percent mean short term load versus time curve ( Figure 4 20 ) were displayed on the screen for real time feedback. The latest data readings were displayed on the screen and each data reading was automatically recorded in a Microsoft Excel spreadsheet. Test specimen conditioning program A LabVIEW 8.6 program developed for this project w as used to monitor the test specimen during conditioning. Concrete specimen temperature as well as the temperature and humidity of the environmental chamber were recorded at five minute intervals. A concrete specimen temperature versus time graph was dis played on the screen for real time feedback. The latest data readings were displayed on the screen

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182 and each data reading was automatically recorded in a Microsoft Excel spreadsheet. Since the three large concrete test specimens used for the test series 1 (baseline) short term (reference) tests were conditioned simultaneously, one concrete test specimen was monitored during conditioning and all three were checked prior to testing. Installation P rocedure The standard installation procedure is described below which was followed for test series 1, 12, 14, 15, and 16. Exceptions to this standard installation procedure as used in test series 7, 9, and 13 follow. Standard baseline installation procedure All anchors were installed according to the manufacturer s specifications. The holes were created with a 3/4 (11/16 for adhesive A) carbide tipped concrete bit as specified by the manufacturer using a HiltiTM model TE52 hammer drill. A drilling jig ( Figure 4 21) with a depth stop was used to ensure that the holes were drilled perpendicular to the surface of the concrete and to the correct depth. The spoil at the concrete surface was removed with a v acuum prior to cleaning the holes. The holes were cleaned according to the MPII which generally included, blowing with oilfree compressed air, brushing with a steel brush provided by the manufacturer, and then blowing again with compressed air until no dust was discharged. Durations and numbers of brushing/blowing cycles varied by manufacturer, but for each case the holes were cleaned according to the MPII. Details of the full cleaning procedure are listed in Table 4 4 To prevent dust from blowing into the operators mouth and eyes, an adaptor for the vacuum ( Figure 4 22) was us ed to capture the dust ejected from the hole when

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183 blowing with compressed air. This adaptor attached to the vacuum hose and allowed the compressed air nozzle to be easily inserted and removed. Once clean, masking tape was placed over the hole to ensure that dust and humidity did not enter the hole prior to installation of the adhesive anchor. In all cases the time between cleaning and installation was not more than a few minutes. A hole was gently cut in the masking tape prior to installation. The adhesi ve products were dispensed with a manufacturer supplied cartridge gun. According to the manufacturers specifications, several squeezes of adhesive were discharged and disposed of before dispensing into the holes to ensure that the adhesive was of uniform color and consistency indicating that it was properly/thoroughly mixed. The anchors were wiped clean with acetone and allowed to air dry. The anchors were then attached to an embedment depth chair ( Figure 4 23) set for the appropriate embedment depth of 3 1/8. The chair rested on the face of the concrete test specimen ensuring the proper embedment depth and did not interfere with the adhesive squeeze out. The anc hor rod was rotated counterclockwise and jiggled while it was installed in the hole until the legs of the chair came to bear on the concrete. The anchors were left undisturbed during the specified gel/working time and the adhesive was allowed to cure for seven days prior to conditioning. Excess adhesive was carefully chipped away from around the anchor prior to conditioning. The masking tape left around the hole prevented the concrete from being removed during chipping. Test s eries 7 ( m oisture during i nstallation) i nstallation p rocedure This installation procedure was adapted from ACI 355.411 7.10 and 7.6.

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184 The holes were initially drilled to roughly half the final diameter using a 3/8 diameter carbide tipped concrete bit. A water dam ( Figure 4 24) constructed out of 2x4 dimensional lumber was secured to the top of the concrete test specimens with silicon. The holes were filled with water and the test specimens were covered with 3 of water for a minimum of eight days (192 hours). Following eight days of saturation, the water was drained and the standing water was vacuumed out of the holes and the installation procedure then followed the above described standard baseline installation procedure. Test series 9 ( r educed h ole c leaning) i nstallation p rocedure ACI 355.411 7.5 defines a reduced hole cleaning effort as 50% of the full hole cleaning procedure. The standard install ation procedure was followed except tha t the cleaning effort was modified to the procedures described in Table 4 5 Test s eries 13 ( t ype of d rilling) i nstallation p rocedure The holes were created with a 3/4 (11/16 for adhesive A) diamond core bit using a HiltiTM model DD130 core drill. A drilling rig ( Figure 4 25) was used to ensure that the holes were drilled perpendicular to the surface of the concrete. The drilling rig was secured to the concrete specimen with ratchet tiedown straps. The cores were wet drilled by use of a water jacket attached to the chuck of the drill. Efforts were made to reduce the amount of excess water on the concrete specimens. A water collector ( Figure 4 26) connected to a wet vacuum surrounded the bit to collect water during drilling. Tape was placed on the core drill to indicate the proper depth during drilling. The holes were drilled to a depth of 4- to ensure that the core cylinders would break below the required embedment depth. The cylinders were broken off by inserting a

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185 small screwd river in the hole and gently prying the cylinders loose. An extraction tool ( Figure 4 27) was used to remove the cylinder pieces from the hole. Standing water was removed using a wet vacuum with a narrow hose attachment. The holes were then flushed twice using a diameter rubber hose at normal street water pressure and the excess water was captured with the water collector, then brushed twice, and then flushed tw ice again until the water ran clear. Finally, the standing water was removed with a wet vacuum. The holes were cleaned according to the MPII as presented in Table 4 4 The holes were then dried with compressed air by inserting and removing a special air nozzle tip ( Figure 4 28 ) two times. The holes were covered with masking tape to ensure that dust and humidity did not enter the hole prior to installation of the adhesive anchors. The anchor installation proceeded as described earlier in the standard installation procedure. Specimen C onditioning Upon completion of the seven day adhesive curing period, the test specimens were wheeled into the 110F 35% humidity environmental test chamber on dollies for conditioning. The temperature of the concrete test specimen and the environmental chamber as well as the humidity in the environmental chamber were monitored and recorded. Testing began upon completion of the 24 hour conditioning period in the environmental test chamber. Testing P rocedure The standard testing procedures for the short term (reference) and sustained load (creep) tests are described below which was followed for test series 1, 7, 9, 12, 13, 14,

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186 and 15. Exceptions to these standard testing procedures as used in test series 16 follow. Standard short term (reference) test procedure A 0.03 thick PTFE confining sheet and steel 5/8 thick confining plate were placed over the anchor and the nonrigid coupler was attached to the anchor. A 1/16 to 1/8 gap was left between the confining plate and the coupler to allow for rotation of the coupler in order to prevent bending forces from being transferred between the anchor and the loading rod. The short term (reference) test apparatus was placed over the anchor as discussed earlier. Steel spacers were placed under the linear potentiometers so that the initial position reading was in the 0.300 0.500 range (this was done because the position readings at the far extremes of the instrument are less accurate). The Enerpac model RCH 603 Holl O Cylinder 60 ton hydraulic ram was placed on the frame and connected to the Enerpac model P802 10,000 psi hydraulic hand pump. The loading rod was then connected to the coupler. The Houston Scientific model 3500 100kip load cell was placed on top of the ram sandwiched between four 1/4 plates (two above and two below). The loading rod nut was hand tightened t o remove slack in the system. The LabVIEW 8.6 program was started to confirm that the program was functioning correctly and that the linear pot values were within acceptable ranges. The program was then reset and the test was star ted. Pumping did not start until after a few seconds in order to read the initial load reading and to allow the program to zero out the initial load cell and linear pot readings in order to calculate load and displacement.

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187 The anchors were loaded at a constant load rate. The operator adjusted the pump rate to conform to an ideal pump rate that would cause failure at the expected load within 120 seconds by following the ideal load rate curve on the load versus time plot on the screen. The operator was only in the environmental chamber to disconnect and connect the testing apparatus to the anchors. The pumping and test observation was conducted outside the chamber. The LabVIEW 8.6 program automatically recorded the test data in a M icrosoft Excel spreadsheet. Test series 16 ( unconfined) test procedure The above procedure was followed with the following exceptions: The PTFE confining sheet and 5/8 thick steel confining plate were eliminated. The test frame supports were placed no closer than two times the e mbedment depth from the anchor. Standard s ustained l oad ( c reep) t est p rocedure The tests began by placing the 0.03 thick PTFE confining sheet, 5/8 thick steel confining plate, coupler and linear potentiometers as described in the short term (reference) t est procedure. The compression springs were compressed in an INSTRON System 3384 150KN universal loading machine and the load was monitored with the onscreen display from the universal testing machine. Once the desired load was obtained the four corner nuts on the test frame were handtightened to maintain the load. The compression spring frame was placed over the anchor and the loading rod was connected to the coupler. Two steel plates and a washer were placed on top of

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188 the test frame and a nut was loosely placed on top. The entire assembly was rolled into the testing chamber on a dolly for conditioning. Once the 24 hour condition period elapsed, the hydraulic jack chair ( Figure 4 4 ) was placed over the loading rod and a steel loading plate was placed on top. The Houston Scientific model 3500 100kip load cell was placed on top of the loading plate sandwiched between four plates (two above and two below). Another nut was placed on top and hand tightened. The LabVIEW 8.6 program was started to confirm that the program was functioning correctly and that the linear pot values were within acceptable ranges. The program was then reset and the test was started. The data acquisition system initially entered a loading cycle in which the load was monitored by the load cell. The load was applied by pumping the E nerpac P 14 hand pump which displaced the top plate of the test frame causing the load to be transferred from the corner bolts to the loading rod. After the desired load was reached, the nut at the top plate of the test frame was hand tightened and the program exited the loading cycle. The pressure was released from the hand pump and the hydraulic jack chair and load cell were removed from the test frame. The load was thereafter calculated from the spring stiffness and anchor displacement. If it became necessary to add load during the duration of the test, the hydraulic jack chair and load cell were placed on top of the test frame as described above. The program entered a tightening phase in which the load was monitored once again by the load cell and the spring stiffness and displacement. The greater of the two values was used as the load on the anchor. Once the desired load was achieved, the nut on the

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189 top plate of the test frame was hand tightened, the pressure was released from the pump, and the test continued as described above. The LabVIEW 8.6 program automatically recorded the test data in a M icros oft Excel spreadsheet. Test series 16 ( unconfined) test procedure The above procedure was followed with the following exceptions: The PTFE confining sheet and 5/8 thick steel confining plate were eliminated. The test frame supports were placed no closer than two times the embedment depth from the anchor. The compression spring frame was placed on top of a steel plate that rested on the test frame supports. Post test p rocedure A few of the anchors were cored with a 2- diameter concrete cylinder core bit using a Cincinnati Bickford coring machine. The resulting cores were saw cut on each side to the depth of the anchor and then split open. The resulting concrete core provided a more detailed investigation of the failure mode and is discussed in C hapter 5 Photos were taken of the cores and are presented in A ppendix E Anchor Pullout Tests University of Stuttgart The description of the test program conducted at the University of Stuttgart Intsitt fr Werkstoffe im Bauwesen (IWB) to investigate the ef fect of various parameters on the sustained load performance of three adhesive anchor systems is included in Appendix B

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190 Adhesive Alone Tests University of Florida The description of the test program conducted at the University of Florida to investigate the isolated sustained load and short term creep behavior of the adhesive alone is included in Appendix C Early Age Concrete Evaluation University of Stuttgart This section presents the test program conducted at the IWB laboratory at the University of S tuttgart to investigate the effect of early age concrete on the short term bond strength of three adhesive anchor systems. Overview The early age concrete investigation is identified as test series 17. Refer t o Table 3 2 for a complete description of the test program. The short term (reference) confined tests generally followed the test procedure found in ASTM E488. Anchors were installed in concrete slabs of various ages (3, 6, 13, 20, & 27 days) and tested 24 hours later. Their short term bond strength as well as other parameters (compressive strength, split tensile strength, initial surface absorption, hardness, and internal concrete temperature and relative humidity) were measured. Test A pparatus This section describes the test apparatus used for early age concrete evaluation used at the IWB laboratory at the University of Stuttgart. Short term ( r eference) a nchor p ullout t est a pparatus The testing apparatus for the short term (reference) test ( Figure 4 29 ) used a 3.5 diameter x 0.04 thick Teflon PTFE (Polytetrafluoroethylene) confining sheet with a 1 diameter hole in the middle placed under an 1.2 thick steel equilateral triangle (12 sid es) confining plate. The confining plate had an insert with a 13/16 (20mm) diameter

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191 hole to fit around the anchor. The confining sheet was used to correct for any surface irregularities in the concrete. A tripod was placed on the confining plate which supported a 22kip hydraulic ram, bearing plate, 45kip load cell, and a ball and socket hinge plate. The anchor was connected to a pulling assembly through a 0.55 (14mm) hole and secured with two high strength nuts. The pulling assembly was connected t o a 5/8 (16mm) diameter loading rod which passed though the ram, load cell, and ball and socket hinge above and was secured with a nut. A separate rig ( Figure 4 30) held an LVDT which was connected via a steel cable to a magnet placed on top of the anchor. Initial surface absorption test apparatus An initial surface absorption test (ISAT) apparatus ( Figure 4 31) provided by IMPACT Test Equipment Ltd. was used to evaluate the initial absorption of the top formed surface of the concrete as well as the surfaces of the drilled hole. This apparatus cons isted of a reservoir of water which maintained an 8 (200mm) head above the surface of the concrete. The reservoir was attached to a 3.3 (85mm) diameter clear cap secured to the surface of the concrete by a clamp and screws with plastic inserts. A small capillary tube was also connected to the cap in order to provide precise measurements of water flow at specific times. Rebound hamme r A rebound hammer by Suspa DSI GmbH ( Figure 4 32 ) was used to measure the concrete hardness. This hammer would drive a weight into the surface of the concrete by means of a spring and record the rebound distance. A scale on the side of the hammer could be used to determine the hardnes s in terms of a 6 cube compressive strength.

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192 Indention hammer An indention hammer ( Figure 4 33) was also used to measure the concrete hardness. This hammer would drive a 0.4 (10mm) diameter ball into the surface of the concrete by means of a spring. The average diameter of the indention would be measured and a graph could be consulted to determine the hardness in terms of a 6 cube compressive strength. Specimen P reparation The test specimens consisted of three parts; the concrete test member, the adhesive, and the anchor rod. Concrete test member The concrete test members for the early age concrete investigation tests were poured in 50 x 50 x 16 high density overlay plywood forms. Minimal reinforcement of two 6mm steel reinforcing bars w as placed along the top and bottom edges for crack control. Two diameter by 9.5 long PVC pipes with PVDF filter covers were placed in one corner at 1.5 and 3 from the t op test surface to allow for temperature and humidity sensors to be placed later. Four temperature and humidity sensors were cast into one slab but were destroyed during casting. All the test blocks were cast on July 8, 2011 at the Friedrich Rau GmbH & Co precast concrete plant in Ebhausen, Germany. In order to provide a smooth testing surface the blocks were cast upside down against the high density overlay plywood. Concrete with round river gravel without any admixtures was specified with a mean compressive strength between 3630 5080 psi during testing. The slump measured 1.5 and the casting temperature was 68F. Both 4 x 8 cylinders and 6 cubes were cast.

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193 On July 9, 2011, the day after casting, the forms were removed and the slabs were sh ipped to the IWB laboratory in Stuttgart, Germany on July 11, 2011, the third day after casting. The concrete test members were maintained in the IWB laboratory thereafter. The 4 x 8 cylinders and 6 cubes were delivered to the MPA laboratory at the Un iversity of Stuttgart for compression and split tensile testing. Concrete compressive strength was determined by testing both the 4 x 8 cylinders in general accordance with ASTM C39 and the 6 (15cm) cubes in general accordance with DIN EN 123903. Spli t tensile strength was determined by testing both the 4 x 8 cylinders in general accordance with ASTM C496 and the 6 cubes in general accordance with DIN EN 123906. The compression and split tensile tests were conducted at the MPA testing laboratory at the University of Stuttgart on a Form+Test Prfsysteme universal testing machine ( Figure 4 34) calibrated by MPA in May 2011. The cylinders were ground smooth on a Form+Test Seidner cylinder grinding machine ( Figure 4 35) prior to testing. Concrete compression and split tensile versus age relationships were determined by test ing at 4, 7, 14, 21, and 28 days. Table 4 6 and Table 4 7 present the compres sion strength and split tensile strength results respectively for the 4x8 cylinders and 6 concrete cubes. Moist cured cubes typically test about 15% stronger than moist cylinders (Mehta and Monteiro (2006)) due to more confinement based on their geomet ry. The cubes and cylinders in this test program tested from 30% to 40% higher than the cylinders. This can be explained by the fact that these specimens were all air cured and the different volume to surface area ratio of the two different specimens. C ubes have a larger volume to

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194 surface area and thus will dry slower than cylinders resulting in higher compressive strengths. Adhesive The same three adhesives identified earlier were used in this portion of the project. The three adhesive products were st ored in the IWB laboratory and maintained within the temperature and humidity range specified by the manufacturers prior to installation. Anchor r ods The anchor rods were grade 14.9 (203 ksi (1400 MPa) 90% yield strength) (12mm) diameter steel threaded rod fabricated by Hersteller. This grade of steel had a specified yield strength of 183 ksi and a specified tensile strength of 203 ksi. The anchor rods were cut to a length of 6.7 from 8 stock and the top end ground and chamfered with a bench grinder and steel brush to remove burrs and to clean up the threads in order to install the nuts. The bottom end of the anchor was ground to a 45 cone ( Figure 4 36 ) in order to fit into a centering guide placed at the bottom of the drilled hole. Instrumentation Measurement Displacement. Direct measurement of the anchor displacement was measured by a Novotechnik LVDT. The LVDT was mounted in a separate rig and connected via a steel cable to a magnet placed on the top of the anchor ( Figure 4 30). Load. The tension in the anchor was measured indirectly as a compressive reaction of the hydraulic ram in the test apparatus. The load was measured by a Hottinger Baldwin Messtechnik 45 kip load cell. The load cell was excited and measured by the NI DIAdem software.

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195 Temperature and r elative h umidity. Internal temperature and relative humidity in each concrete test slab was measured by Sensiron SHT71 temperature and humidity sensors. Four sensors were cast within one control slab and two empty PVC pipes were cast into every test slab to allow for later insertion and removal of additional sensor s if necessary. The four Sensiron SHT71 sensors cast directly into the concrete slab were constructed similar to those as discussed by Rodden (2006). Each sensor was placed in a 4 long diameter PVC pipe. One end was covered with a Polyvinyldenfluorid (PVDF) filter by Thomapor with 0.2 m openings. The other end was packed with foam insulation and a PVDE disk to provide a backing for a silicon seal. The entire assembly ( Figure 4 37) was later wrapped with duct tape for extra protection. The pipes were tied to rebar and the centerlines were placed 1.5 and 3 below the top of the testing surface, 2- from each other, with the center of the entire assembly 8 from the corner ( Figure 4 38). Two 9.5 long by diameter PVC tubes with the same PVDF filter on one end and covered with duct tape were cast in each test slab. The pipes were attached to a plastic plate with holes taped over and connected to the side of the form. The pipes were tied to rebar and the centerlines were placed at 1.5 and 3 below the top of the testing surface and 9.5 and 10.5 from the corner of the slab ( Figure 4 38). The Sensiron SHT71 sensors were inserted into the test slab after casting and several days prior to testing and packed with foam insulation and sealed with duct tape. The sensors were monitored by the Sensiron EK H4 evaluation kit and recorded to a text file.

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196 Ambient temperature and relative humidity of the laboratory was monitored and recorded by a Lufft Opusio sensor at 10 minute intervals. Time. Time was measured using the computers internal clock. Instrument c alibration Displacement. The LVDTs were calibrated by IWB every three months against calibrated ceramic gages over their working range of 10mm at 2mm increments. Load. The Hottinger Baldwin Messtechnik 45 kip load cell was calibrated on December 11, 2009 by MPA. The load cell was calibrated over a range of 0 to 45 kips with data points every 4.5 kips. Temperature and h umidity. The Sensiron SHT71 temperature and humidity sensors we re calibrated by the factory. The Lufft Opusio ambient temperature and humidity sensor was calibrated by IWB on January 22, 2010 against a TESTO calibrated temperature gage. Data M anagement and A cquisition An NI DIA dem 10.2 program ( Figure 4 39) was used for the short term (reference) tests in one of five test cabinets which included a computer, data acquisition hardware, and two hydraulic pumps. Load and displacement were recorded at 0.2 second intervals and a load versus displacement curve was displayed on the screen for real time feedback. Load was applied by a hydraulic pump and controlled by valves integral with the test cabinet. The latest data readings were displayed on the screen and the data was recorded to a Microsoft Excel spreadsheet following the test. Installation P rocedure The installation procedure generally followed the procedure described in Appendix B except the anchors were allowed to cure for 24 hours prior to testing.

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197 Testing P rocedure Short term (reference) test procedure A 0.04 thick PTFE confining sheet and 1.2 thick steel confining plate with 13/16 (20mm) diameter hole insert were placed over the anchor and the pulling assembly was attached to the anchor. A 3/16 gap was left between the confining plate and the pulling assembly to allow for rotation of the coupler in order to prevent bending forces from being transferred between the anchor and the loading rod. The short term (reference) test apparatus was placed over the anchor. The LUKAS Hydraulik GmbH 22kip hydraulic ram was placed on the tripod and connected to the test cabinet hydraulic pump. The loading rod was then connected to the coupler. The Hottinger Baldwin Messtechnik 45kip load cell was placed on top of a loading plate on top of the ram. A ball and socket hinge was placed on top of the load cell and the loading rod nut was hand tightened to remove slack in the system. A magn et was placed on top of the anchor and connected to a Novotechnik LVDT mounted in a separate rig via a cable The load and displacement values were the zeroed in the NI D IA dem 10.2 program. The test was started and load rate was controlled by the operator to achieve a failure in one to three minutes. Initial surface absorption test procedure Initial surface absorption was measured in general accordance with BS 1881 using an ISAT apparatus provided by Impact Test Equipment Ltd. A 3.3 (85mm) diameter plasti c cap was clamped to the top surface of the concrete with a steel bar using screws and plastic inserts. This cap was connected via rubber tubes to a reservoir of water and a capillary tube. The reservoir maintained an 8 (200mm) head of water during the

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198 duration of the test. At 10 minutes, 30 minutes, and 60 minutes the tube connecting the reservoir to the cap was clamped allowing water to flow into the cap from a capillary tube. A scale created from the calibration procedure in BS 1881 was used to determine the amount of water entering the cap over a 1 minut e period. Three repetitions were conducted on the top formed surface of the concrete test block. A modified ISAT was developed to determine the initial surface absorption of the sides and bottom of a hole drilled in concrete. Three 0.55 (14mm) diameter by 4.5 (115mm) deep holes were drilled and cleaned according to the cleaning procedure for adhesive A. The 3.3 (85mm) diameter cap was clamped over a hole and the same procedures for the above des cribed ISAT were performed. The initial surface absorption of the sides and bottom of the drilled hole were determined by removing the influence of the top formed surface of the concrete specimen based on the tests performed on the top surface only. An al lowance was made for the chipped area around the top of the hole ( Figure 4 40) as this surface would be more similar to the side of the hole than to the top formed sur face. The diameter of the chipped area was measured in four directions ( Figure 4 41) and their results averaged to determine an equivalent circular area. The initial surface absorption is defined as the rate of flow of water into concrete per unit area at a stated interval from the start of the test and at a constant applied head (BS 1881). BS 1881 presents the standard initial surface absorption test (ISAT). The ISAT is intended to be used on a flat surface of concrete. Below is the rationale behind the development of a modified ISAT of bore holes for adhesive anchor testing. In general, the initial surface absorption can be calculated as:

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199 = (4 1) where: I = initial surface absorption [ml/m2s] V = volume of water measured in the capillary [ml] A = surface area through which water is passing [m2] t = measured time interval (60 seconds) [s] For the standard ISAT on the top formed surface of concrete the equation can be written as: = (4 2) where: I1 = initial surface absorption of the top formed surface [ml/m2s] V1 = volume of water measured in the capillary [ml] A1 = surface area of the reservoir [m2] t = measured time interval (60 seconds) [s] For adhesive anchor applications it is desirable to determine the initial surface absorption of the surfaces of the drilled hole. In order to determine this, the ISAT reservoir was placed over a hole drilled in concrete and the initial surface absorption of the water passing through the combined surface area of the top formed surface and the surfaces of the drilled hole is defined as: = (4 3) where: I2 = initial surface absorption of the top formed s urface and hole combined [ml/m2s] V2 = volume of water measured in the capillary [ml] A2 = surface area of the top formed surface and the hole combined [m2] t = measured time interval (60 seconds) [s]

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200 During drilling it is common that the top surface of t he concrete w ould chip or spall around the edge of the hole. For this reason it is desirable to divide the total surface area ( A2) into distinct areas ( Figure 4 42): = + + (4 4) where: AS = area of the un chipped top formed surface [m2] AC = chipped area of the spalled top surface around the hole due to drilling [m2] AH = area if the sides and bottom of the drilled hole [m2] It is reasonable that the initial surface absorption of the surfaces of the drilled hole ( AH) is different than that of the top formed surface ( AS). Furthermore, it was assumed that the chipped area ( AC) is more similar to that of the sides and bottom of the drilled hole ( AH) than to the top surface of the concrete ( AS). Therefore the areas AC and AH can be combined into another area ( ACH) where: = + (4 5) Where ACH = area of the c hipped surface and drilled hole [m2] This combined area ( ACH) will have a distinct initial surface absorption ( ICH) different than that of the top surface of the concrete ( IS). It is also reasonable then to assume that the initial surface absorption ( I1) is the same as the initial surface absorption of the unchipped top surface portion ( IS), or, = (4 6) Substituting Equation 42 and Equation 43 into Equation 4 6 = (4 7) Solving for VS,

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201 = (4 8) It is obvious that the total volume of water ( V2) is the sum of the volume of water passing through the distinct parts of the wetted surface, or, = + + (4 9) where: VS = volume of water passing through the unchipped top formed surface [ml] VC = volume of water passing through the chipped area of the spalled top surface around the hole [ml] VH = volume of water passing through the area if the sides and bottom of the drilled hole [ml] Combining VC and VH, = + (4 10) Where VCH = volu me of water passing through the area of the c hipped surface and drilled hole [ml] Substituting Equation 48 into Equation 410, = + (4 11) Rearranging, = (4 12) Referring to Equation 41 the initial surface absorption of the chipped are and the hole can be written as, = (4 13)

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202 Substituting Equation 412 and Equation 45 into Equation 413, the initial surface absorption of the surface of the drilled hole plus the chipped area around the edge of the hole can be defined as: = [ + ] (4 14) Rebound hammer test procedure Concrete hardness was measured with a rebound hammer in general accordance with ASTM C805 using a Suspa DSI GmbH Original Schmidt hammer. The hammer was used in the vertically downward position in the general location of the installed anchors. These tests were conducted after the anchor pullout tests in case the hammer caused cracking in the early age concrete. The average of ten readings was reported and a 6 cube concrete compressive strength was estimated using a scale provided by the manufacturer. Indention hammer test procedure Concrete hardness was also measured with an indention hammer in general accordance with DIN 4240. The hammer was used in the vertically downward position on the full load setting in the general location of the installed anchors. These tests were conducted after the anchor pullout tests in case the hammer caused cracking in the early age concrete. As allowed by the test standard, carbon paper was used to better distinguish the indention. Two orthogonal diameters were measured of each indention and their values averaged. The average of twenty readings was reported and a 6 cube concrete compressive strength was est imated using a scale provided by the manufacturer.

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203 Roughness Three additional 0.55 ( 14mm ) diameter and 3.75 ( 95mm ) deep holes were drilled and cleaned according to the cleaning procedure for adhesive A for a hole roughness investigation. These holes wer e then stuffed with a 1- square piece of foam insulation an d sealed with silicon to prevent the entrance of slurry during coring. The holes were then cored with a 4 diameter core drill using a HiltiTM DD130 core drill. The cores were then split open ( Figure 4 43 ). It was intended to measure the roughness of the sides of the hole with a Perthometer and then using laser profilometry at the I nstitt fr Technische Opt ik (I TO ) laboratory at the University of Stuttgart. However, after repeated attempts the laboratory did not have the ability to perform these tests. Short Term Anchor Pullout Data Reduction The following provides information related to data reduction. Di splacement a djustments While the anchors were initially loaded, the system took up slack producing large initial displacement readings. Instead of adjusting the displacement readings for the initial slack in the system during testing, all data was recorded and adjustments were made after testing. The data acquisition system did however zero out the first position reading from the linear potentiometers (linear pots) and all displacements readings were calculated from that initial position reading. The init ial displacement readings were later adjusted to account for the slack in the system by extending a secant line through the loaddisplacement curve to the x axis to determine the x intercept ( Figure 4 44). The secant line intersected the load-

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204 displacement curve at approximately 10% and 30% of the peak load. The x intercept was then used to adjust the loaddisplacement curve to intersect the origin. The displacement readings were also adjusted for the strain in the anchor between the concrete surface and the coupler. This was accomplished by adjusting the displacement reading by subtracting a strain correction factor ( ) multiplied by the load reading. cor adjN disp disp where: dispadj = displacement adjusted for strain in anchor disp = unadjusted displacement N = load E A le cor where: l = distance between top of concrete and coupler Ae = effective area of anchor E = modulus of elas ticity of anchor steel For the 5/8 diameter anchor pullout tests at the University of Florida: l = 2 in Ae = 0.226 in2 E = 29,000 ksi = 0.000305 in/kip For the 12mm diameter anchor pullout tests at the University of Stuttgart: l = 3.54 in (90mm) Ae = 0.131 in2 (84.8 mm2) E = 29,000 ksi (200 GPa) = 0.000929 in/kip (0.0053 mm/kN) Determining short term load strength The short term load strength is the strength of an adhesive determined from the short term load test. Due to vari ous possible failure modes, this might not be the

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205 maximum short term load. The mean short term load (MSL) is the average of the short term adhesive strength values for an adhesive determined from a series of short term load tests. This value is used to determine the percent load values in the sustained load (creep) test. There are several methods available to analyze the loaddisplacement behavior of a short term load test in determining the short term load strength which is referred to as Nadh by ACI 355.4 11. ACI 355.411 10.4.4 presents the following procedure: Determine a tangent stiffness at 30% of the maximum short term load ( Nu) which is typically approximated as the secant stiffness from the origin to the point on the loaddisplacement curve at 0.30Nu. If the displacement at 0.30Nu is less than 0.002 in, the origin is shifted to the point on the loaddisplacement curve at 0.30Nu Multiply the tangent stiffness by 2/3 and project this line until it intersects with the loaddisplacement curve Nadh i s taken at the intersection if the load at the intersection is less than Nu Nadh is taken as Nu if the load at the intersection is greater than Nu This method was analyzed and was not recommended, as it tended to drastically underestimate the short term lo ad strength in a few cases as can be seen in Figure 4 48. Another procedure was presented by Cook and Konz (2001), in which they classified three types of loaddispla cement response (strengthcontrolled, stiffness controlled, and displacement controlled) and described methods to determine the short term load strength for each type of situation. The responses and methods of analysis are summarized below: Strength contr olled. This failure mode is defined by a very sharp peak in the loaddisplacement curve with a drastic reduction in the stiffness of the adhesive anchor beyond the peak. The short term load strength is determined to be at the peak on

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206 the loaddisplacemen t graph. Figure 4 45 shows a typical curve of a strengthcontrolled failure. Stiffness controlled. This failure mode is defined by a large initial st iffness and a drastic change in stiffness, which does not decrease but rather continues to increase at a lower slope. Due to the absence of a peak in the curve, the short term load strength is determined by finding the point at a tangent stiffness of 30 kips/in (5 kN/mm). The tangent stiffness (slope) at a given data point can be approximated by calculating the slope between a point five data points after and five data points before a given point. Figure 4 46 shows a typical curve of a stiffness controlled failure. Displacement controlled. This failure mode has a loaddisplacement curve with a relatively constant stiffness above the stiffness controlled threshold of 30 kips/in (5 kN/mm). The maximum short term load occurs at very high, and impractical, displacement s. In this case, the short term load strength is set at a point with a displacement of 0.1 in (2.5mm). While the 0.1 in displacement seems arbitrary, this failure mode usually only occurs in inferior products. Since this research was limited to products that had passed ICC ES AC308 (ACI 355.411) this failure mode was not expected and was not observed. Figure 4 47 shows a typical curve of a displace ment controlled failure. The method presented by Cook and Konz (2001) exhibited better results than the ACI 355.411 approach and was the approach chosen for the project. Figure 4 48 is a loaddisplacement graph for a short term load test conducted showing the short term load strength calculated by three different methods. The ACI 355.411 procedure estimated Nadh as 11,100 lbf. The strength controlled method estimated Nadh as 19,905 lbf. The stiffness controlled method estimated Nadh as 19,751 lbf. For each test, the short term load strength was recorded and the mean short term load for each adhesive was determined from the average of the tests. Short term b ond s tress The short term bond stress ( adh) was calculated as the short term load strength ( Nadh) divided by the adhesive bond area at the interface with the anchor Aadh, where: Aadh = ef d = diameter of anchor (0.625 at UF and 0.472 at US) hef = embedment depth of hole (3.125 at UF and 3.150 at US)

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207 The short term bond stress was calculated to compare the results between the laboratories at the University of Florida and the University of Stuttgart as different diameters and embedment depths were used. Sustained Load Anchor Pullout Data Reduction The following provides information related to determining the time to failure. Time to failure was initially evaluated as both the onset of tertiary creep and as the time to rupture. Based on recommendations from NCHRP (2009) the change in slope method was used to determine the onset of tertiary creep. This method calculated the slope at a given point as the slope between it and the prior data point. The change in slopes between the given point and the following data point was plotted and examined over the region just prior to rupture. It was suggested that this examination be conducted on a normal graph (not semi log ). The rupture point was easily identified on the disp lacement ver sus time graph by its near vertical slope. A suggested range for examining the change in slope was from 80% to 100% of time to rupture. Due to minor fluctuations in the displacement readings, the slope might change from positive to negative several times over this range. Tertiary creep was defined as the time the change in slope became positive for the last time prior to rupture. This method produced favorable results and a sample graph is shown as Figure 4 49. The time to rupture was identified as the point when the anchor pulled out of the hole, which is indicated by a vertical line on the displacement versus time graph. This proved to be a very easy and reproducible analysis and did not vary significantly from the initiation of tertiary creep. Both times were determined for each test and the values

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208 for the UF and US baseline series are listed in Appendix F. Apart from a few exceptions, there was an average 3% difference between the two values. In three cases there was a larger difference, but this was for three tests at US and was due to the very short failure time (20 minutes) in relation to the sampling resolution of 10 minutes. As the time t o rupture and onset of tertiary creep analysis produced essentially the same time to failures, it was decided to use the time to rupture as the determination of time to failure as it was a much simpler method. The sustained load tests for TS16 (unconfined setup) exhibited bond failure with small shallow cones with circular cracks around the anchor at approximately 1hef from the center of the anchor ( Figure 4 50). The majority of the anchors in the unconfined sustained load tests did not exhibit a quick increase in displacement rate just prior to failure as had been observed in previous confined sustained load tests. Beyond cracking, the anchor continued to provide som e resistance to load due to friction and possibly partial adhesion along the sides. Since the test setup used a spring, after the concrete cracked and the anchor displaced, the load would continue to drop ( Figure 4 51). The load displacement response coupled with the relaxation of the spring made it difficult to identify the point of tertiary creep according to the procedure described earlier. This became problematic as the load on the anchor at final rupture was significantly less than what was initially applied. A special procedure for TS16 was developed to identify the time to failure. The time to failure was determined as the time when the displaceme nt of the sustained load test reached the average displacement from the short term tests (0.03 in) as indicated in Figure 4 52

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209 Assessment of a Parameters Impact on Sustained Load Performance Test series 1 16 and 21 22 evaluated a parameters influence on sustained load performance using the stress versus timeto failure test method (either by anchor pullout tests or dogbone tensile creep tests) which provided a straight forward method to evaluate the performance of adhesive anchors under sustained load. Unlike the displacement projection test method found in ASTM E1512, ICC ES AC58, ICCES AC308, and ACI 355.4 11, the stress versus time to failure method does not rely upon projections of measured displacements but simply records the time to failure of the anchor. The only disadvantage of this method is that it takes an unknown time to complete the tests since they are all conducted to failure. If a given parameter has the same effect on the bond strength in the long term as it does in the short term, then the alpha reduction factor at a given timeto failure should be the same as the short term alpha reduction factor evaluated at two minutes. Figure 4 53 shows the basic concept behind the use of the stress versus timeto failure test method to evaluate the effect of a particular parameter on the sustained load performance of an adhesive anchor. First, a baseline stress versus timeto failure test series is performed for each adhesive product. Series 1, 2, and 21 (one series per laboratory) included short term tests (five repetitions) and sustained load tests at reduced stress levels. A baseline stress versus timeto failure relationship is shown as the solid line in Figure 4 53. Note that sam ple data points are not included in Figure 4 53 for clarity. For analysis purposes, an alphabaseline curve can be created on the stress versus time to failure plot ( Figure 4 53) in which the alpha reduction factor at any given time to failure is identical to the short term alpha reduction factor. The stress versus

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210 time to failure relationship for a given parameter established from experimental data can therefore be compared to the alphabaseline curve. If at any given point in time, the stress level to cause failure predicted by the alphabaseline is greater than the prediction from the trend of experimental data, then the parameter has an adverse effect on the sustained load performance of an adhesive anchor. This can also be visualized by normalizing the stress levels predicted by the alphabaseline by the experimentally predicted stress levels at a given time, as illustrated in Figure 4 54. If the normalized value is greater than one, then the parameter has a more adverse effect in the long term than predicted by the short term alpha reduction f actor. Conversely, normalized values less than one indicate that the given parameter does not have a more adverse effect on the sustained load performance. Recommendations In case of an eccentricity with the loading rod in the sustained load anchor pullout test procedure performed at the University of Florida, one of the two linear potentiometers could produce a negative displacement reading which might generate an error in the averaged displacement. It is suggested that either one linear potentiometer be placed concentric with the anchor axis or a coupler with three linear potentiometers be used. Summary A general overview of the test program and analysis procedures was presented in this chapter The following chapter s discuss the findings and applications.

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211 Table 4 1 Test descriptions Test s eries Test d escription 1 Baseline 7 Moisture during Installation 9 Reduced h ole c leaning 12 Standard DOT mix 13 Type of d rilling 14 Concrete c omposition f ly a sh 15 Concrete c omposition b last f urnace s lag 16 Test s etup u nconfined Table 4 2 Concrete pour details Concrete m ix Pour d ate Number of s hort term t est m embers Number of s ustained load test m embers Notes A May 18, 2010 3 12 B May 26, 2010 3 12 C June 2, 2010 3 12 D June 15, 2010 3 8 E June 22, 2010 3 9 F June 29, 2010 3 9 G July 27, 2010 3 9 H August 3, 2010 3 12 20% f ly a sh I August 10, 2010 3 12 50% b last f urnace s lag J March 25, 2011 3 12 Standard DOT mix Table 4 3 Concrete series average compressive strength Concrete mix Pour d ate Average c ompressive s trength (psi) 7 day 14 day 28 day 56 day 112 day 224 day 448 days Final h No of days i A 5/18/ 2010 3180 3930 4200 4350 4480 4460 b 3870 c 4210 679 B 5/ 26 / 2010 3170 3950 4260 4390 d d d 4100 671 C 6/ 2 / 2010 3260 3840 4410 4340 a 4210 4140 3830 3960 664 D 6/ 15 / 2010 3180 4080 4320 4800 d d d 4740 651 E 6/ 22 / 2010 3130 3790 4210 4430 d d d 4570 644 F 6/ 29 / 2010 2660 3670 4050 4290 4500 d d 4310 637 G 7/ 27 / 2010 3100 3810 4260 4720 4650 4570 d 4470 609 H (FA e ) 8/ 3 / 2010 2220 3010 3610 3810 3500 3760 d 3540 602 I (BFS f ) 8/ 10 / 2010 1710 2740 3240 3460 3000 3020 d 2700 595 J (DOT g ) 3/ 25 / 2011 4530 5490 5940 5930 5310 5540 j 4830 368 a Test conducted at 55 days b Test conducted at 231 days c Test conducted at 251 days d Not enough samples to conduct tests at these times, last group of three samples held until end of project e FA = Fly Ash f BFS = Blast Furnace Slag g DOT = Department of Transportation concrete mix h Samples tested at end of project on March 27, 2012 i Number of days since casting for final compression test j Test at 448 days not conducted

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212 Table 4 4 Full hole cleaning procedures per MPII Adhesive A Adhesive B Adhesive C Blow with compressed air (4x) Brush with drill (4x) Blow with compressed air (4x) Blow with compressed air (2x) Brush by hand (2x) Blow with compressed air (2x) Blow with compressed air (4x) Brush with drill (1x) Blow with compressed air (4x) Brush with drill (1x) Blow with compressed air (4x) Brush with drill (1x) Blow with compressed air (4x) Brush with drill (1x) Blow with compressed air (4x ) Table 4 5 Reduced hole cleaning procedures Adhesive A Adhesive B Adhesive C Blow with hand pump (2x) Brush with drill (2x) Blow with hand pump (2x) Blow with hand pump (1x) Brush by hand (1x) Blow with hand pump (1x) Blow with compressed air (2x) Brush by hand (1x) Blow with compressed air (4x) Brush by hand (1x) Blow with compressed air (4x) Table 4 6 Early age concrete compression strength results Age (days) 4x8 cylinders (psi) 6 cubes (psi) Ratio cubes/cylinders 4 2080 2790 1.34 7 2350 3280 1.40 14 2850 3860 1.35 21 3040 4090 1.35 28 3250 4230 1.30 Table 4 7 Early age concrete split tensile strength results Age (days) 4x8 cylinders (psi) 6 cubes (psi) Ratio cubes/cylinders 4 200 260 1.30 7 250 270 1.08 14 270 330 1.22 21 290 300 1.03 28 270 290 1.07

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213 Figure 4 1 Short term (reference) confined test apparatus Figure 4 2 Test series 16 short term (reference) unconfined test apparatus

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214 Figure 4 3 Sustained load (creep) confined test apparatus Figure 4 4 Test frame with hydraulic jack chair shown in red (photo courtesy of author)

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215 Figure 4 5 Test series 16 sustained load (creep) unconfined test apparatus Figure 4 6 Concrete test specimens being cast (photo courtesy of author)

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216 Figure 4 7 Ovens (photo courtesy of author) Figure 4 8 Mixer (photo courtesy of author)

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217 Figure 4 9 Compression machine (photo courtesy of author) Figure 4 10. Cylinder grinding machine (photo courtesy of author)

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218 Figure 4 11. Walk in stability chamber (photo courtesy of author) Figure 4 12. Left side of testing chamber (photo courtesy of author)

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219 Figure 4 13. Right side of testing chamber (photo courtesy of author)

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220 Figure 4 14. Layout of anchor pull out test frames in the stability chamber

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221 Figure 4 15. Data sampling LabVIEW program Figure 4 16. Short term test LabVIEW program (main screen)

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222 Figure 4 17. Short term test LabVIEW program (chart page) Figure 4 18. Sustained load test LabVIEW program (main screen)

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223 Figure 4 19. Sustained load test LabVIEW program (displacement plot) Figure 4 20. Sustained load test LabVIEW program (percent load plot)

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224 Figure 4 21. Drilling rig and hammer drill (photo courtesy of author) Figure 4 22. Vacuum adaptor (photo courtesy of author)

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225 Figure 4 23. Embedment depth chair (photo courtesy of author) Figure 4 24. Water dam for test series 7 installation (photo courtesy of author)

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226 Figure 4 25. Core drill for test series 13 (photo courtesy of author) Figure 4 26. Water collector (photo courtesy of author)

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227 Figure 4 27. Extraction tool (photo courtesy of author) Figure 4 28. Air nozzle (photo courtesy of author)

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228 Figure 4 29. Short term testing apparatus (photo courtesy of author) Figure 4 30. LVDT rig (photo courtesy of author)

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229 Figure 4 31. ISAT equipment (photo courtesy of author) Figure 4 32. Rebound hammer (photo courtesy of author)

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2 30 Figure 4 33. Indention hammer (photo courtesy of author) Figure 4 34. MPA universal testing machine (photo courtesy of author)

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231 Figure 4 35. MPA cylinder grinding machine (photo courtesy of author) Figure 4 36. Anchor showing 45 cone to fit into centering guide (photo courtesy of author)

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232 Figure 4 37. Sensiron sensor assembly (photo courtesy of author) Figure 4 38. PVC pipes and Sensiron sensors placed in forms prior to casting (photo courtesy of author)

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233 Figure 4 39. Screenshot of NI DIAdem 10.2 data acquisition program Figure 4 40. Chipped area around top of hole (photo courtesy of author)

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234 Figure 4 41. Jig to measure the diameter of the chipped area in four directions (photo courtesy of author) Figure 4 42. A2 sub areas

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235 Figure 4 43. Core with drilled hole split for roughness evaluation (photo courtesy of author) Figure 4 44. Removing the effect of slack in the loaddisplacement graph

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236 Figure 4 45. Typical strengthcontrolled failure [Reprinted, with permission, from Cook, R.A. and Konz, R.C. (2001). Factors Influencing Bond Strength of Adhesive Anchors. ACI Structural Journal 98(1), pp. 76 86. ] Figure 4 46. Typical stiffnesscontrolled failure [Reprinted, with permission, from Cook, R.A. and Konz, R.C. (2001). Factors Influencing Bond Strength of Adhesive Anchors. ACI Structural Journal 98(1), pp. 76 8 6. ]

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237 Figure 4 4 7 Typical displacement controlled failure [Reprinted with permission from Cook, R.A. and Konz, R.C. (2001). Factors Influencing Bond Strength of Adhesive Anchors. ACI Structural Journal 98(1), pp. 76 86. ] Figure 4 48. Example of calculating short term load strength from various methods

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238 Figure 4 49. Example of the change in slope method Figure 4 50. Typical TS16 sustained load bond with shallow cone failure (photo courtesy of author)

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239 Figure 4 51. Test series 16 (unconfined setup) sustained load tests percent MSL versus time plot Figure 4 52. Test series 16 (unconfined setup) sustained load tests displacement versus time plot

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240 Figure 4 53. Stress versus time to failure comparison of experimental, baseline and alphabaseline trends Figure 4 54. Influence Ratio of alphabaseline

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241 CHAPTER 5 ANCHOR PULLOUT TEST RESULTS This chapter presents the results of the short term and sustained load anchor pullout tests conducted at the University of Florida and the University of Stuttgart. The results of the early age concrete investigation are presented in Appendix I The tests were labeled with a series of letters and numbers. The short term load tests are identified as TS A ST R, where: TS: Test Series (0116, 21, 22) A: A dhesive type (A, B, or C) ST: Signifies short term test R: Test repetition number ( 1 13) The sustained load tests are identified as TS A PPR, where: TS: Test Series (0116, 21, 22) A: A dhesive type (A, B, or C) PP: Signifies stress level percentage (85, 75, 65, etc.) R: Test repetition number (1 15) Short Term Anchor Pullout Load Testing The short term load tests were conducted as described earlier The following provides the test results. Short term Load Test Results The load displacement graphs along with the peak load and displacement values for the short term load tests conduc ted at the University of Florida and the University of Stuttgart are included in Appendix D Statistical analysis The results of a statistical analysis for each test are presented in Table 5 1 through Table 5 6 for the tests conducted on adhesives A through C at the University of Florida and the University of Stuttgart respectivel y to compare the baseline short term

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242 test results to the short term test results for each parameter. The statistical analysis includes the mean, standard deviation, and coefficient of variation for each data set. An alpha reduction factor is also calculated as the mean of a particular test series divided by the mean of its respective baseline test series. A one sided student t test with a confidence interval of 90% was conducted on each test series against its respective baseline test series to determine if the results of a particular test series were significantly different from its respective baseline test series. A one sided t test was chosen with the null hypothesis that the mean of a test series was not less than the mean of the baseline. A 90% conf idence interval indicates a 10% significance level ( = 0.10 in t test table). Therefore, if the p value from the t test was less than the significance level, then the null hypothesis was rejected and the parameter test data sets were significantly differ ent than the baseline test data sets. As the short term tests for TS 3, 4, 8, 10, and 11 were conducted later in the testing program, a few baseline short term tests were conducted near the end of the project to investigate if the short term bond strength changed relative to age and/or strength of concrete. Two repetitions of adhesive A and three repetitions of adhesive B were conducted at the University of Florida and at the University of Stuttgar t. The results are presented in Appendix D and Table 5 7 Due to the 20% increase in baseline strengths for the specimens at the University of Stuttgart, the alpha factors and sustained load tests for TS 3, 4, 8, 10, and 11 were referenced to the later short term tests. The short term results and resulting al pha factors for these tests are presented in Table 5 8 and Table 5 9

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243 The 20 % increase in bond strengths at the University of Stuttgart wa s most likely due to the increase in concrete strength between the two testing dates. While the concrete strengths for the specimens at University of Florida stayed consistent within the testing period, the concrete strengths at the University of Stuttgart increased approximately 50% over the course of the project. This wa s most likely due to the CEM I 32.5R cement used in Stuttgart which was a blended cement that may have contained pozzolans. Bond stress analysis As the tests at the University of Florida and the University of Stuttgart were conducted with different anchor diameters and embedment depths, the short term bond stress was calculated for the baseline tests series 1 and 2 for comparis on. For adhesive A and B the means of the bond stresses determined by the University of Stuttgart (US) and the University of Florida (UF) were very close 98% and 99% respectively. The ratio of the means for Adhesive C was 92%. Table 5 10 and Figure 5 1 compares the bond stress results from both laboratories. The means are plotted with an error bar indicating one standard deviation spread above and below the mean. The stressdisplacement graphs along with the peak stress and displacement values for the short term load tests conducted at the Universit y of Florida and the University of Stuttgart are included in Appendix D Discussion on u n confined r esults At the time of installation and testing for test series 16 (unconfined setup) the concrete compressive strength was 4360 psi. The confined bond strengths as determined from the short term baseline tests were as follows:

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244 = 3225 = 4180 = 4290 Due to the high confined bond strength of these adhesives it was anticipated that concrete breakout failure would occur for the standard 5/8 x 3.125 anchor used in the unconfined short term tests. Taking a coefficient for mean concrete breakout strength of k = 35 from Fuchs et al. ( 1995) the predicted concrete breakout strength ( Ncb) was: = = 35 4360 ( 3 125 ) = 12 800 = 12 8 Assuming a 0.75 ratio ( ACI 355.4 11 10.4.5.1 ) of unconfined bond strength to confined bond strength to determine the unconfined bond strength ( Na) from a series of confined tests for each adhesive was: = = 0 75 = 0 75 ( 3225 ) ( 0 625 ) ( 3 125 ) = 14 800 = 14. 8 = 0 75 ( 4180 ) ( 0 625 ) ( 3 125 ) = 19 200 = 19 2 = 0 75 ( 4290 ) ( 0 625 ) ( 3 125 ) = 19 700 = 19 7

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245 For the tests, highstrength steel was used to prevent yielding during testing (ASTM A354 grade BD) with a tensile strength fu = 150 ksi and a yield strength fya = 130 ksi. The steel yield strength of a 5/8 diameter ( Ase = 0.226 in2) threaded rod ( Nsa) is: = = ( 0 226 ) ( 130 ) = 29 4 As a result, the unconfined short term tests were expected to exhibit concrete breakout at around 13 kips. The short term tests results for test series 16 ( unconfined setup) are presented in Table 5 1 Table 5 2 and Table 5 3 The anchors were installed in test slabs with a min imum edge distance of 2.56hef and spacing from the anchor to the test frame of 2hef which wa s greater than or equal to the 2 hef requirement in ASTM E48810 As indicated in Table 5 1 Table 5 2 and Table 5 3 the failure loads were less than the expected 13 kips from concrete breakout for all products. The anchors had an apparent bond failure mode characterized by a shallow cone at the top and a bond failure along the lower portions of the anchor. As the alpha setup ratios (0.53, 0.43, and 0.37) were much less than the accepted ratio of 0.75, a series of verification tests was conducted as described below A series of short term tests with adhesive C was conducted in higher strength (6550 psi) concrete to verify the short term results for test series 16. For the new concrete blocks, the predict ed concrete breakout strength ( Ncb) was: = = 35 6550 ( 3 125 ) = 15 600 = 15 6

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246 The short term tests results for test series 16 verification tests at 110 F are presented in Table 5 11 and Figure 5 2 The short term tests results for test series 16 verification tests at 80 F are presented in Table 5 12 and Figure 5 3 The anchors were installed in test slabs with a minimum edge distance of 4hef and spacing from the anchor to the test frame of 2 hef which wa s greater than or equal to the 2 hef requirement in ASTM E488 10 The mean of the unconfined tests results of the verification tests was 9.7 kips at 110F and 11.1 kips at 80F which we re simila r to the previous test results of 9.8 kips and well below the expec ted concrete breakout strength of 15.6 kips and the expected unconfined bond strength using a 0.75 ratio of unconfined to confined of 19.7 kips The alpha reduction factor for the verification tests was 0.41 at 110F and 0.40 at 80F. This indicates that for unconfined tests temperature does not have an effect and the alpha setup factor is well below the assumed 0.75, and lies within the range of 0.35 to 0.55 for these products Selection of Adhesive for Sustained Load Investigation The determination of which adhesive to test for sustained load performance for test series 5 7, 9, and 12 16 was based on the lowest alpha reduction factor. A summary of the alpha reduction factors is presented in Table 5 13 and accompanying Figure 5 4 The adhesives chosen for sustained load evaluation are identified in Table 5 13. The NCHRP panel initially recommended testing two adhesives for sensitivity to installation direction, therefore two adhesives were chosen for test series 5 and 6. Adhesive A was chosen as it exhibited the lowest alpha reduction factor. Near the end of the project, it was decided not to test a second adhesive for test series 5 and 6 as (1)

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247 the results from the sustained load results for adhesive A did not s how a significant difference from the baseline and (2) in order to complete the testing program due to the longer than anticipated test durations. The adhesives chosen for sustained load investigation for test series 3 and 4 were based on the lowest glass transition temperature ( Tg). The glass transition temperatures for each adhesive based on DSC analysis conducted at the University of Florida are presented in Table 5 14 Adhesive B was chosen for investigation for sustained load sensitivity for test series 3 and 4. The adhesive chosen for sustained load investigation for test series 8 was based on the adhesive that was most sensitive to alkalinity. The manufacturer s provided the results from the alkalinity sensitivity slice tests found in ICC ES AC308 9.8. The results are summarized in Table 5 15 Adhesive B was chosen for investigation for sustained load sensitivity for test series 8. It was initially decided to choose the adhesive for sustained load investigation for test series 10 and 11 based on the lowest degree of cross linking. The values for the degree of cross link ing for each adhesive based on DSC analysis conducted at the University of Florida are presented in Table 5 16. However, the adhesive with the lowest degree of cross linking had a relatively high temperature for the lowest permissible temperature installation temperature. Table 5 17 summarizes the lowest permissible installation temperatures. Adhesive A was chosen for investigation for sustained load sensitivity for test series 10 and 11 as it had the second lowest degree of crosslinking and the lowest permissible installation temperature.

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248 Sustained Load Anchor Pullout Testing T he sustained load (creep) tests were conducted as described earlier The following provides the test results of the sustained load tests. Modification to Testing Program It was initially decided to test the baseline series at 85%, 75%, 65%, and 55%. However due to very early failures in the 85% and 75% stress levels, it was decided to test adhesives A, B, and C at 45% and adhesive A at 35%. Near the end of the project, several more tests were conducted at the higher stress levels ~65% 85% to reexamine the early failures. Additionally, test series 316 were initially scheduled to be tested at three different stress levels. Based on the above discussion, the stress lev els were reduced to 70%, 55%, and 40%. Due to the longer than anticipated failure durations, it was decided by the researchers with the NCHRP p anel approval to test some series at only two stress levels. Sustained Load Displacement versus Time Test Result s The displacement versus time results for the anchor pullout tests conducted at the University of Florida and the University of Stuttgart are presented in Appendix G. A sample is provided as Figure 5 5 It can be seen from the sample plot that the higher stress level tests have steeper slopes (creep rate) and fail quicker than the lower stress level curves with shallower slopes. Core S ample A nalysis S everal anchors with surrounding concrete were cored from the concrete test blocks and then split open for investigation of the failure surface. Most were anchors that had failed but a few were anchors from tests that were terminated before failure.

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249 The photos and discussion can be found in Appendix E Only a few typical examples will be discussed here. Several anchor tests that were terminated prior to failure were investigated and two different events occurred when splitting the core sample. The adhesi ve B samples ( Figure 5 6 ) fractured through the concrete on one side of the anchor indicating that the adhesive bond between adhesive B and the steel and the concrete as well as the internal cohesive bonds were stronger than the tensile strength of the concrete. Adhesive C samples ( Figure 5 7 ) separated between the steel and the adhesive indicating that bond between adhesive and the concrete was stronger than the bond between the adhesive and the steel. For short term and sustained load tests where failure occurred, two common failure modes were loss of adhesion with the concrete ( Figure 5 8 ) and shearing failure of the adhesive along the threads ( Figure 5 9 ). A common variant of the adhesive bond failure above was seen in many tests in which, in some cases, it appears the adhesion with the concrete failed and a plug of the anchor with the adhesive still attached slipped in the hole. In other cases, port ions of the adhesive also fractured within the bond line. This adhesive plug eventually stopped due to friction and reduction in load as the spring relaxed. As the anchor remained in the chamber, portions of the adhesive plug appeared to reattach to the concrete. When the sample was later cored and split, either portions of the adhesive detached from the threads or portions of the concrete fractured. The reattachment can be supported by the fact that many of the samples in Appendix E show large displ acements (1/2 1) after failure with one side still attached

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250 to the core after splitting. It is not reasonable that the adhesive could displace this much and stay bonded to the concrete and steel. Rather the adhesive would have to debond and/or fracture, shift, and then reattach. Many of the samples remained in the 110F chamber for a few days prior to removal. Additionally, many of the cores were not made until months after the tests concluded. This provided ample time at elevated temperatures for the adhesive to reattach. X ray Investigation of Failure Surface As it i s difficult to determine the initial failure surface due to the destructive nature of failure, it was decided to investigate the condition of the adhesive just prior to failure by use of an x ray computed tomography (CT) system by North Star Imaging, Inc. ( Figure 5 10) at the Advanced Materials Characterization Laboratory (AMCL) at the University of Florida. Three anchors were installed with adhesive B into extra test blocks made from the DOT mix (mix J ). The anchors were installed and conditioned similar to the baseline and test series 12 (DOT mix). Two specimens were loaded with a continuous load rate similar to the short term load test procedure and the load was released just prior to failure on one specimen and well beyond failure on the other. Another specimen was loaded to 80% MSL and maintained with a hand pump and the load was r eleased just prior to failure. The three specimens were then cored with a 2.5 core bit and viewed in the x ray CT system using a 225kV x copper filter for better resolution.

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251 Short term L oad T est S pecimen ( P re failure) Figure 5 11 pre sents the load versus displacement curve for the short term load test for the x ray sample that was stopped prior to failure. Three x ray images were taken of the specimen at 0, 120, and 240 as shown in Figure 5 12 When removing the core from the test block, the core broke at the base of the anchor. The anchor rod and the concrete can clearly be seen in the three views. A slightly lighter band can be seen next to the anchor where the adhesive is located. No cracks we re visible in the adhesive. This could be explained in two ways. One, the x ray CT system wa s not able to distinguish a crack in the adhesive due to the low density of the adhesive. The other explanation could be that there we re no cracks and the adhesive had only plastically deformed at th at point. Sustained L oad T est S pecimen ( P re failure) Figure 5 13 presents the displacement versus time curve for the sustained load test for the x ray sample that was stopped prior to failure. The load was released just p rior to failure as evidenced by the increased displacement rate. Three x ray images were taken of the specimen at 0, 120, and 240 as shown in Figure 5 14. Unlike the previous core, the core for this sample broke well below the end of the anchor when removed from the test block In these views, it can be seen that the hole was drilled about deeper than the embedment depth. The space below the anchor was filled with adhesive and it c ould be seen where the anchor pulled away from the adhesive below as evidenced by the lighter color just below the anchor. Several cracks c ould be seen in the concrete at the surface where the small cone broke within the bounds of th e confining plate hole. As with the previous sample, no cracks we re visible within the adhesive around the sides of the anchor.

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252 Short term L oad T est S pecimen ( P ost failure) In order to determine if cracks in the adhesive can be detected by the x ray CT sy stem, a third specimen was loaded well beyond failure ( Figure 5 15). The increased initial stiffness in this sample as compared to the prefailure sample was most likely due to a higher degree of curing as this was tested 24 hours after the other two specimens therefore it had 48 hours of conditioning at 110F. However, as this wa s a failure investigation to determine if cracks we re visible by the x ray CT system and not a comparison of bond strengths, the different stiffness wa s not important. Three x ray images were taken of the specimen at 0, 120, and 240 as shown in Figure 5 16. As in the previous x ray images, no cracks in the adhesive c ould be distinguished in this specimen. Cracks in the concrete near the surface c ould be seen due to the formation of the small cone within the bounds of the confining plate hole. Findings from X ray S tudy This limited study on the x ray CT system did not provide an indication on the location of first cracking in anchors loaded just prior to failure both under short term and sustained loads as no cracks were visible within the adhesive. A third specimen was loaded well beyond failure to verify if the x ray CT system was capable to distinguish cracks within the adhesive. However, no cracks were discernible within the adhesive of this third specimen. Fur ther research could be conducted to determine if other experimental techniques or capabilities of an x ray CT system can be used to distinguish cracking in an adhesive anchor system just prior to and just after failure in order to determine the initial failure surface.

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253 Summary The following observations from the anchor pullout tests were made: The short term anchor pullout tests conducted at the University of Florida and the University of Stuttgart used different anchor diameters and embedment depths, but the bond stress values were in close agreement The results from the unconfined short term tests seem to indicate that the 0.75 ratio of unconfined bond strength to confined bond strength in ACI 355.411 and ACI 318 11 to determine the unconfined bond strength from a series of confined tests might be a significant overestimate of unconfined bond strength. T ests on the three adhesives in this research project produced factors of 0.53, 0.43, and 0.37. Additional verification tests in higher strength concrete were conducted to verify the reduction factor s. These verification tests at 80F and 110F resulted in alpha factors of 0.40 and 0.41 respectively The alpha setup factor for the relationship between unconfined to confined bond strength in ACI 355.411 s hould be adjusted or a test series added to determine this relationship for individual products The results of this research showed that this value can be in the range of 0.35 to 0.55 and is significantly less than t he value of 0.75 currently assumed in ACI 355.4 11. Several anchors were cored and split open for investigation of the adhesive failure surface. Two com mon failure modes were observed: loss of adhesion with the concrete and shearing failure of the adhesive at the threads Also observed was that it appeared an adhesive/anchor plug would detach from i ts original location and shift upward in the hole. An x ray CT system was used to investigate the location of initial cracking in two adhesive anchor specimens loaded just prior to failure under both short term and sustained loading The x ray CT system was unable to discern cracks in the adhesive. A third specimen was loaded well beyond failure to ensure cracking and the system was also unable to discern cracks within the adhesive. X ray CT sc anning techniques could be further investigated to attempt to determine the location of first cracking and the failure surface in adhesive anchors under load prior to failure.

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254 Table 5 1 Statistical analys is for short term tests on adhesive A at University of Florida Test s eries Mean (kips) std. dev. (kips) C o V alpha reduct. factor t test p value a Significantly different? 1 Baseline (reference) 19.8 1.1 0.06 7 Moisture (installation) 16.2 0.9 0.06 0.82 0.00 YES 9 Hole c leaning (reduced) 18.4 0.8 0.04 0.93 0.01 YES 12 Concrete m ix (DOT) 16.6 2.6 0.15 0.84 0.02 YES 13 Type of d rilling (cored) 11.9 1.5 0.12 0.60 0.00 YES 14 Concrete m ix (FA) 18.5 1.2 0.07 0.93 0.04 YES 15 Concrete m ix (BFS) 17.4 0.7 0.04 0.88 0.00 YES 16 Test set up (unconfined) 10.4 0.3 0.03 0.53 0.00 YES Notes: a Student's t test is one sided at a confidence level of 90% Table 5 2 Statistical analysis for short term tests on adhesive B at University of Florida Test s eries Mean (kips) std. dev. (kips) C o V alpha reduct. factor t test p value a Significantly different? 1 Baseline (reference) 25.7 1.3 0.05 7 Moisture (installation) 24.1 1.4 0.06 0.94 0.03 YES 9 Hole c leaning (reduced) 23.8 1.4 0.06 0.93 0.02 YES 12 Concrete m ix (DOT) 22.4 2.0 0.09 0.87 0.01 YES 13 Type of d rilling (cored) 18.7 1.7 0.09 0.73 0.00 YES 14 Concrete m ix (FA) 23.4 2.9 0.12 0.91 0.08 YES 15 Concrete m ix (BFS) 25.5 0.5 0.02 0.99 0.39 NO 16 Test set up (unconfined) 11.0 1.0 0.09 0.43 0.00 YES Notes: a Student's t test is one sided at a confidence level of 90%

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255 Table 5 3 Statistical analysis for short term tests on adhesive C at University of Florida Test s eries Mean (kips) std. dev. (kips) C o V alpha reduct. factor t test p value a Significantly different? 1 Baseline (reference) 26.3 1.7 0.06 7b Moisture (installation) 24.2 0.9 0.04 0.92 0.01 YES 9 Hole c leaning (reduced) 21.3 1.4 0.06 0.81 0.00 YES 12 Concrete m ix (DOT) 25.1 1.0 0.04 0.95 0.05 YES 13 Type of d rilling (cored) 23.2 0.2 0.01 0.88 0.00 YES 14 Concrete m ix (FA) 26.5 0.6 0.02 1.01 0.37 NO 15 Concrete m ix (BFS) 24.8 0.8 0.03 0.94 0.02 YES 16c Test set up (unconfined) 9.8 0.9 0.09 0.37 0.00 YES Notes: a Student's t test is onesided at a confidence level of 90% b Repetition 4 of tests series 7 is considered an outlier and is not included in statistical calculations. c Repetition 5 of tests series 16 is considered an outlier and is not included in statistical calculations. Table 5 4 Statistical analysis for short term tests on adhesive A at University of Stuttgart Test s eries Mean (kips) std. dev. (kips) C o V alpha reduct. factor t test p value a Significantly different? 2 Baseline (reference) 14.7 0.6 0.04 5 Installation direction (horizontal) 15.8 0.5 0.03 1.07 0.01 YES 6 Installation direction (overhead) 16.1 0.6 0.04 1.09 0.00 YES Notes: a Student's t test is onesided at a confidence level of 90% b Test series 3, 4, and 8 were determined from other criteria as discussed later Table 5 5 Statistical analysis for short term tests on adhesive B at University of Stuttgart Test series mean (kips) std. dev. (kips) C o V 2 Baseline (reference) 19.3 0.7 0.04

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256 Table 5 6 Statistical analysis for short term tests on adhesive C at University of Stuttgart Test series mean (kips) std. dev. (kips) C o V 2 Baseline (reference) 18.5 1.0 0.05 Notes: Adhesive C was not used for sustained load investigation Table 5 7 Comparison of late baseline tests to initial baseline tests Lab a dhesive 1 Date of t esting Mean (kips) St d. dev (kips) C o V Ratio of final/initial UF A (initial) 8/2010 19.8 1.1 0.06 0.93 UF A (final) 4/2012 18.3 0.4 0.02 UF B (initial) 8/2010 25.7 1.3 0.05 0.94 UF B (final) 4/2012 24.1 3.4 0.14 US A (initial) 8/2010 14.7 0.6 0.04 1.17 US A (final) 4/2012 17.2 0.8 0.05 US B (initial) 8/2010 19.3 0.7 0.04 1.19 US B (final) 4/2012 22.9 0.4 0.02 Notes: UF = University of Florida, US = University of Stuttgart Table 5 8 Statistical analysis for late short term tests on adhesive A at University of Stuttgart Test s eries Mean (kips) std. dev. (kips) C o V alpha reduct. factor t test p value a Significantly different? 2 Baseline (reference) 17.2 0.8 0.05 10 Installation temperature (MFR min/MFR min) 18.9 0.8 0.04 1.10 0.06 YES 11 Installation temperature (MFR min/110F) 14.8 0.6 0.04 0.86 0.05 YES Notes: a Student's t test is one sided at a confidence level of 90%

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257 Table 5 9 Statistical analysis for late short term tests on adhesive B at University of Stuttgart Test s eries Mean (kips) std. dev. (kips) C o V alpha reduct. factor t test p value a Significantly different? 2 Baseline (reference) 22.9 0.4 0.02 3 Service temperature (>120F) 23.1 0.4 0.02 1.01 0.29 NO 4 Service temperature (70F) 27.2 0.6 0.02 1.19 0.00 YES 8 Moisture (service) 24.4 0.7 0.03 1.07 0.00 YES Notes: a Student's t test is one sided at a confidence level of 90% Table 5 10. Bond stress analysis Lab a dhesive Mean (psi) Std dev (psi) C o V Ratio of means US/UF UF A 3226 180 0.06 0.98 US A 3153 129 0.04 UF B 4182 218 0.05 0.99 US B 4125 156 0.04 UF C 4293 277 0.06 0.92 US C 3949 204 0.05 Notes: UF = University of Florida US = University of Stuttgart Table 5 11. Test series 16 ( unconfined setup) short term verification tests results with adhesive C in higher strength concrete at 110 F Test setup Test r epetition (kips) Mean STD CoV alpha setup 1 2 3 Confined 22.7 24.8 1.5 23.8 1.4 0.06 Unconfined 10.3 8.9 10.1 9.7 0.7 0.08 0.41 Notes: Test repetition 3 for the unconfined tests was considered an outlier and was not used in the calculation of the mean. Prior to testing, the adhesive was still tacky after a week of curing. After testing, the anchor was removed from the hole and the adhesive was still tacky, indicating that it was not fully cured. Table 5 12. Test series 16 (unconfined setup) short term verification tests results with adhesive C in higher strength concrete at 80 F Test setup Test r epetition (kips) Mean STD CoV alpha setup 4 5 6 Confined 26.4 29.3 28.1 27.8 2.1 0.07 Unconfined 10.2 10.9 12.2 11.1 1.0 0.09 0.40

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258 Table 5 13. Summary of alpha reduction factors Test series Adhesive A Adhesive B Adhesive C UFd USd 3 Service temperature ( 120F) c 1.01 a X 4 Service temperature (70F) c 1.19 a X 5 Installation direction (horizontal) b 1.07 a X 6 Installation direction (overhead) b 1.09 a X 7 Moisture (installation) 0.82 a 0.94 0.92 X 8 Moisture (service) c 1.07 a X 9 Hole c leaning (reduced) 0.93 0.93 0.81 a X 10 Installation temperature (MFR min/MFR min) c 1.10 a X 11 Installation temperature (MFR min/110F) c 0.86 a X 12 Concrete m ix (DOT) 0.84 a 0.87 0.95 X 13 Type of d rilling (cored) 0.60 0.73 a 0.88 X 14 Concrete m ix (FA) 0.93 0.91 a 1.01 X 15 Concrete m ix (BFS) 0.88 a 0.99 0.94 X 16 Test set up (unconfined) 0.53 0.43 0.37 a X Notes: a Adhesives chosen for investigation of se nsitivity to sustained loading b Adhesive A was chosen for test series 5 & 6 based on separate preliminary reference tests c Test series 3, 4, 8, 10, & 11 used other criteria besides the lowest alpha reduction factor to select the product for sustained load investigation as discussed below. Therefore only the alpha reduction for the product selected was determined. d UF = University of Florida, US = University of Stuttgart Table 5 14. Glass transition te mperatures Parameter Adhesive A (C) Adhesive B (C) Adhesive C (C) Week cure 52 51 55 Notes: a Adhesive B chosen for testing b Values obtained from DSC tests performed at the University of Florida Table 5 15. Alkalinity sensitivity reduction factor Parameter Adhesive A Adhesive B Adhesive C Alkalinity sensitivity 0.95 0.86 1.00 Notes: a Adhesive B chosen for testing b Values provided by the manufacturers

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259 Table 5 16. Degree of cross linking Parameter Adhesive A (%) Adhesive B (%) Adhesive C (%) Week cure 95.4 96.3 87.8 Notes: a Adhesive A chosen for testing b Values obtained from DSC tests performed at the University of Florida Table 5 17. Lowest manufacturer specified installation temperature Parameter Adhesive A (C) Adhesive B (C) Adhesive C (C) Installation t emperature 0 5 10 Notes: a Adhesive A chosen for testing

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260 Figure 5 1 Bond stress analysis Figure 5 2 Test series 16 ( unconfined setup) short term verification tests results with adhesive C in higher strength concrete at 110 F

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261 Figure 5 3 Test series 16 (unconfined setup) short term verification tests results with adhesive C in higher strength concrete at 80F Figure 5 4 Summary of alpha reduction factors per test series

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262 Figure 5 5 TS02B (US b aseline B) l oad versus displacement plot Figure 5 6 Typical terminated sample for adhesive B (photo courtesy of Kunal Malpani)

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263 Figure 5 7 Typical terminated sample for adhesive C (photo courtesy of Kunal Malpani) Figure 5 8 Typical adhesive bond failure (photo courtesy of Kunal Malpani)

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264 Figure 5 9 Typical shearing failure at threads (photo courtesy of Kunal Malpani) Figure 5 10. University of Florida computed tomography x ray system [ Reprinted with permission from North Star Imaging, Inc. An ITW Company (www.4nsi.com) ]

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265 Figure 5 11. Load versus displacement plot for x ray investigation short term load test stopped prior to failure A B C Figure 5 12 X ray scans of short term load test on adhesive B stopped prior to failure at A) 0 rotation B) 120 rotation and C) 240 rotation

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266 Figure 5 13. Displacement versus time plot for x ray investigation sustained load test on adhesive B stopped prior to failure A B C Figure 5 14 X ray scans of sustained load test on adhesive B stopped prior to failure at A) 0 rotation B) 120 rotation and C) 240 rotation

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267 Figure 5 15. Load versus displacement plot for x ray investigation short term load test on adhesive B continued past failure A B C Figure 5 16 X ray scans of short term load test on adhesive B continued past failure at A) 0 rotation B) 120 rotation and C) 240 rotation

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268 CHAPTER 6 S TRESS VERSUS TIME TO FAILURE AND SUSTAINE D LOAD INFLUENCE RESULTS The stress versus time to failure results for the anchor pullout tests conducted at the University of Florida and the University of Stuttgart are presented in Appendix H. Model Equation for Stress versus Timeto Failure Relationship The SvTTF projection as listed in AASHTO (2010c) TP 84 10, recommends a logarithmic model for predicting the Stress versus Time to Failure relationship. For comparison, a logarithmic model ( = ( ) + ) and a power model ( = ) were both evaluated and they resulted in essentially the same coefficient of determination ( R2). It was decided to use the logarithmic model as recommended in AASHTO (2010c) TP 84 10. Exclusion of Short term Tests in Stress versus Time to Failure Relationship The short term tests were initially expected to be included on the SvTTF curve, but based on changes in the distribution of bond stress along the borehole with increasing load, analysis of the test results, and investigation o f failure modes, it was decided to not include the short term test results in the SvTTF projection. Based on analytical work by McVay et al. (1996), Figure 1 4 to Figure 1 7 show that at low stress levels (<30% of MSL) the adhesive is still in the elastic range. At about 70% of MSL, the adhesive has undergone inelastic redistribution of stress along the entire length of the anchor. Under high stress level sustained load conditions, the coupling of creep strains caused by the sustained load and strains caused by inelastic redistribution of bond stres s seem to hasten the failure. As an example, Figure 6 1 and Figure 6 2 show the results of TS01B (Baseline B) with the short term tests excluded and included in the projection respectively By

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269 inspection it can be seen that the trend of the sustained load tests on Figure 6 1 does not intersect the data points of the short term tests at 100% of MSL. Appendix H provides SvTTF figures showing all baseline data with trendlines including and not including the short term tests. Using the constants from the regression analysis, the expected failure stress level for a five minute load duration for TS01B is 79% of MSL. Table 6 1 summarizes the expected failure stress levels at a five minute load duration from the regression analysis for the six baseline tests and from three baselines created by combining the results from US and UF. This reduced expected failure stress level for short duration loads appears to result from a dual requirement placed on the polymer. The magnitude of the load causes the polymer to undergo inelastic deformation as it redistributes the load down the anchor, and the sustained nature of the load causes the polymers to migrate within the adhesive. These two actions occurring simultaneously reduce the capacity. The lower stress level sustained load tests provide sufficient time for the polymer strands within the adhesive to slide past each other. This is supported by the much larger deformations seen in the sustained load tests than in the short term tests as polymer strand migration leads to creep deformation and higher rupture displacements. For the UF baseline tests, the peak displacements in the sustained load tests were approximately 1/3 higher than the peak displacements in the short term tests for adhesive A and double for adhesives B and C ( Table 6 2 and Figure 6 3 ) If the peak displacements in the sustained load are compared to the limiting displacement ( lim) at

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270 loss of adhesion as calculated in ACI 355.411, the ratio for adhesives B and C approach 3 ( Table 6 3 and Figure 6 3 ). Figure 6 4 and Figure 6 5 present the displacements versus timeto failure and %MSL respectively for the short term and sustained load tests for all three UF baseline tests. These figures show that failure displacements are larger for longer timeto failures and lower stress levels. Based on the above discussion, it was decided to exclude the short term test results from the SvTTF relationships in the anchor tests. Subsequently, the analysis for sustained load influence of various parameters was based on projections derived only from sustained load test results. It should be noted that projections were also performed including and ex cluding the short term tests for each test series and similar conclusions were drawn. C hapter 7 includes an investigation into the viscoelastic behavior of adhesive anchors under high stress states using incremental load rate tests and a finite element analysis to further examine the cause of this behavior Combined SvTTF Baseline Curves Figure 6 6 Figure 6 8 present the combined baseline curves from UF and US for the three adhesives. Since different anchor diameters and embedment depths were used at the two laboratories, the stresses have all been normalized by the average of the short term bond stresses of the fifteen baseline tests (10 at UF and 5 at US). Rejection of Failures D uring Loading Several of the tests failed during the loading period prior to reaching the desired sustained load. I t was decided that those tests that failed during loading were not

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271 reliable and were excluded from the time to failure projection. Thes e are noted as Excluded in Appendix H Tests Terminated Prior to Failure Several tests were terminated prior to failur e per approval by NCHRP. These tests were identified as not likely to fail during the remainder of the testing program and their continued monitoring would not provide any more meaningful results than already obtained. The tests identified for early term ination are identified in the SvTTF plots with a diamond and their final test durations listed in the tables in Appendix H. Tests Still Running at Time of Publishing As some sustained load tests ran longer than expected, all data reported is as of June 3, 2012. Those tests that were still running w ere included in the SvTTF plots with the ir current test duration and are identified with a circle and their test durations listed in the tables in Appendix H At the time of publication, TS 10 (manufacturer minimum installation and inservice temperature) had three tests at one stress level underway and three tests at another stress level pending Due to this limited data TS 10 does not have a trendline plotted on the SvTTF chart in Appendix H. Sustained Load Influence Influence Ratio with Actual Alpha Reduction Factors As discussed earlier, the sustained load Influence Ratio to a given parameter can be evaluated by normalizing the alphabaseline stress level by the predicted stress level at a g iven time. If the normalized value is less than one, then the parameter does not have a more adverse effect under sustained load at that point in time than under short -

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272 term load Figure 6 9 presents the results of this analysis for the parameters investigated. Figure 6 10 presents the same information evaluated at 15 years of elevated temperature. ACI 355.411 assumes that a structure exceeds 110F for only 20% of its lifetime, and as a result projects 110F test data to 10 years (20% of 50 years). For an AASHTO lifetime of 75 years, the influence is thus evaluated at 15 years (20% of 75 years) In only two cases was the Influence Ratio greater than one ( 1.2 3 for TS03 (120F service temperature) and 1.0 9 for TS08 ( in service moisture ) ). TS05 (horizontal installation) and TS22 (cure time) had Influence Ratios of 1.00 and 0.99 respectively. Influence Ratio with Alpha Reduction Factors Limited to a Maximum Value of 1 As shown in Figure 5 4 s ome short term tests (TS03, TS04, TS05, TS06, TS08, TS10, and TS22) indicated a slight increase in strength for the given parameter. As design standards should not increase the pre dicted short term strength due to slight variations above the baseline for certain parameters, it would then seem appropriate to evaluate the Influence Ratio of these parameters against the baseline and not against an elevated baseline. This is identical to limiting the alphareduction factor to a maximum value of 1. Figure 6 11 and Figure 6 12 present the Influence Ratios with the alphareduction factors limited to a maximum value of 1. With this adjustment, TS03 (120F service temperature) had a n Influence R atio of 1.2 2 and the I nfluence R atio was essentially 1 ( 1.02) for TS08 (in service moisture) TS05 (horizontal installation) and TS22 (cure time) had Influence Ratios of 0.93 and 0.95 respectively.

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273 As this is more appropriate for design, the practice of limiting the alpha reduction factor to 1 in the analysis of the sustained load Influence Ratio was adopted for the remaining analysis and discussion. Influence Ratio of Nominal Strength ACI 355.411 and 31811 provisions for nominal strength of adhesive anchors are based on a characteristic strength representing a 5% lower fractile and incorporating alpha modification factors for various installation and inservice parameters The characteristic strength representing a 5% lower fractile can be determined from onesi ded tolerance limits for a normal distribut ion as discussed in ACI 355.411 10.3. Assuming a CoV of 0.15 and an infinite number of tests the characteristic strength is 75% of the mean baseline strength. ACI 318 11 D.4.1.2 further applies a sustained lo ad reduction factor of 0.55. A 0.50 sustained load factor is recommended for AASHTO applications due to longer service lives. Therefore the nominal strength for a particular test series can be determined as the baseline characteristic strength adjusted b y the sustained load factor of 0.50 and the applicable alphareduction factor for the given parameter. The Influence Ratios of the nominal stress are all less than one and are presented in Figure 6 13 Stress Versus TimeToFailure and Sustained Load Influence Statistical Analysis A statistical study was conducted on the SvTTF results to evaluate the reliability of the relatively small data sets. Four methods were used and their approach and results are briefly discussed below. The experimental and alphabaseline data can be represented by a general logarithmic equation where = stress, t = time to failure, and m and b are constants of regression. This can be expressed as a linear relationship of the form

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274 y = mx + b where y = stress, x = ln(time to failure), and m and b are the same constants of regression. The constant m is the slope and b is the intercept of the regression line. Me thod 1: Comparison of Slopes Initially it was decided that influence to sustained load would be determined by comparing the slopes of the experimental trendline to the slope of the alphabaseline. If the experimental trendline was shallower (less negative) that the alphabaseline, then the parameter did not adversely affect the sustained load performance. A onesided t test with a confidence level of 90% was conducted on the two slopes with the following hypothesis: Null hypothesis: mexperimental alphabaseline Alternate hypothesis: mexperimental > malphabaseline Therefore, if the probability from the t 0.10) then the null hypothesis is rejected and the slope of the experimental line is significantly higher than the slope of the alphabaseline and the parameter does not adversely affect the sustained load performance. If the probability is less than the significance level, then we fail to reject the null hypothesis and cannot say that the slopes are s ignificantly different. This method was straightforward and produced definitive results on comparing the slopes of the regression lines. However, as the experimental and alphabaseline trendlines do not have the same intercept, this method does not provide an indication of the relationship between the experimental and alphabaseline trendlines at given failure times. Only comparing the slopes is not appropriate as a shallow slope experimental

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275 trendline could plot below the alphabaseline at early failure times, but cross and lie above at later failure times as shown in Figure 6 14 Method 2: Comparison of E xperimental V alues to A lpha baseline As some data points plotted below the alphabaseline for a few test series, the data was also evaluated to determine if the average collection of data plotted above the alphabaseline. This was accomplished by determining the expected stress value predicted by the alphabaseline for each timeto failure in the experimental data set. The residual for each timeto failure was calculated as the difference between the stress value from the experimental data and that predicted by the alphabaseline. The average of these residual s should be greater than zero if the collection of data points lies above the alphabaseline. A one sided t test with a confidence level of 90% was conducted on the residuals with the following hypothesis: Null hypothesis: Alternate hypothesis: mean of residuals > 0 Therefore, if the probability from the t 0.10) then the null hypothesis is rejected and the mean of the residuals is greater than zero and the collection of data points is s ignificantly above the alpha baseline. If the probability is less than the significance level, then we fail to reject the null hypothesis and cannot say that the collection of experimental data is significantly above the alphabaseline. Several of the tes t series had data points that plotted below the alphabaseline at very short failure times and might not be appropriate for inclusion in a statistical analysis

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276 for long term influence Therefore, method 3 is a modification of this method which only includ es data with longer failure times. Method 3: Comparison of Experimental Values Beyond 100 Hours to Alpha baseline Method 3 is similar to method 2, but only includes data points with failure times greater than 100 hours. Method 2 and 3 were straightforward, but for design, we are interested in evaluating the influence at particular structure lifetimes. This was achieved by means of a Monte Carlo simulation as presented in method 4. Method 4: Monte Carlo Simulation to Evaluate Sustained Load Influence Due t o the relatively small data set s (6 17 data points) for each test series, Method 4 evaluate d the statistical significance of the Influence Ratio by conducting a Monte Carlo simulation Each data set was described by a regression line of the form = ml n(t) + b where = stress, t = time to failure, and m and b are the slope and intercept of the logarithmic regression line. The variability of the slopes and the intercepts were de fined by their means and standard deviations. The means were taken as the v alues from the regression analysis. The standard deviations were determined based on Stone and Ellis (2006) as follows: = = where: = = standard deviation of y = ( ) = sum of squares

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277 = ( ) = sum of the squared errors = number of samples = observed value for the independent variable x = mean of the independent variable x = value of the dependent variable y for sample i = estimated value of the dependent variable y for sample i Using the above definitions, the Monte Carlo simulation determined the experimental stress and nominal stress at a lifetime of 75 years for 1,000,000 samples based on normally distributed randomly sampled slopes and intercepts for the experimental and baseline regression lines. As each data set wa s small (6 17 data points), the random values were considered to be Gaussian. The nominal strength was calculated as discussed above. As these exp eriments were conducted at 110F, the data was projected to 20% of the structures lifetime (15 years) as this represents the amount of time that an anchor is expected to be at 110F during its 75 year lifetime. An Influence Ratio for each of 1,000,000 sim ulations was determined and the confidence level evaluated as the percent of the simulations that the Influence Ratio was less than 1. A sensitivity study was conducted on the four random variables in which three were deterministic and the CoV of the fourt h variable was varied (0.01, 0.05, 010, 0.20, and 0.30). In all cases it was shown that the results were more sensitive to the two intercepts than to the two slopes. Generally, the two intercepts had the same or similar sensitivity as was observed for the two slopes. The effect of correlation between the slope and intercept of each line was also investigated. Three simulations were conducted: Correlated samples with a correlation coefficient = 0.5 Uncorrelated samples Correlated samples with a correlation coefficient = 0.5

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278 The results of incorporating correlation into the Monte Carlo simulations are presented in Figure 6 15. The uncorrelated results were on average 3% higher than the positively correlated results with an extreme value of 6% for TS22. The uncorrelated results were on average 3% less than the negatively correlated results, with an extreme value of 9% for TS22. The existence of a positive correlation between the slope and intercept seem s rational based on the physical significance of each param e ter The intercept represent s the stress level at a time to failure of 1 hour. The slope is a representation of the reduction in strength over time. If a good product is defined with a given intercept and slope, then a poorer product would have a lower intercept and a lower (more negative) slope, resulting in a positive correlation between slope and intercept. A negative correlation between slope and intercept i s not rational and therefore the results were rejected. It can be seen that positive correlation did not have a significant effect on the results and therefore the uncorrelated results were u sed in the remainder of the analysis. The uncorrelated results are presented in Figure 6 16 and represent the confidence level that the Influence Ratio of the nominal stress is less than 1 evaluated at 15 years. Table 6 4 presents a summary of the Influence R atios and confidence level s. Discussion on Sustained Load Influence Of all the parameters tested, only two were identified as having an adverse effect on the sustained load performance of ad hesive anchors (120F service temperature and manufacturers cure time). The identification of these two parameters (TS03 and TS22)

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279 as having an adverse effect was based on the Influence Ratio Monte Carlo simulation for confidence level, and an overview of the respective test results. The highest three Influence Ratios were TS03 (1.22), TS08 (1.02), and TS22 (0.95). TS08 (inservice moisture) was not considered adverse as explained below. Parameters with Adverse Sustained Load Influence TS0 3 120 F service temperature. As discussed earlier, polymers exhibit high creep deformations at elevated temperatures. It is no surprise that the long term tests conducted at temperatures above the baseline temperature showed increased creep displacements. TS03 indicated that the stress level predicted by the alphabaseline is 122 % than that to cause failure at an equivalent lifetime of 75 years. The Monte Carlo simulation affirmed that this does have an adverse effect on the sustained load performance based on the low confidence level above the characteristic value. The current testing temperature of 110F was based on temperature measurements provided in a CALTRANS study by Dusel and Mir (1991) of a bridge in Barstow, CA in which 110F was noted to oc cur over a few hours during the day. In the CALTRANS study, there were no recordings greater than 115F. If it can be shown that an anchor would be expected to be at or above 120F, a SvTTF curve c ould be used to determine a reduction factor for inservic e temperature by determining the ratio of stress of the experimental data to the baseline at a given time which is the total amount of time the anchor is expected to be at or above 120F over its lifetime. This might be a relatively short time, on the mag nitude of a few years for a 75 year lifetime. The resulting Influence Ratios would be 1.1 6 for 1 year, 1.1 8 for 2 years, and 1. 20 for 5 years. The corresponding confidence levels are 95%, 93%, and 90% for 1, 2, and

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280 5 years respectively Due to the high confidence levels at these times it seems that for anchors exposed to 120F for a very small percentage of its service life (total of 1 to 5 years), a modific ation factor is not necessary. If it can be shown that an anchor would be expect ed to be at or above 120F for significant portions of its service life, it is recommended that the adhesive anchor system be tested and evaluated for Temperature Category B (ACI 355.4 8.5) at a temperature equal to or greater than its highest service tem perature. TS22 Cure time. While the Influence Ratio of TS22 for adhesive A was less than 1 ( 0.9 5 ) the confidence level that the predicted stress would be greater than the nominal strength was low (69 %). Additionally, the effect of cure time seems to be product specific as adhesive B resulted in a short term alpha reduction factor of 0.54 and was unable to be adequately tested for sustained load at manufacturers cure time to very high deformations. For s ustained load applications it is imp ortant that the adhesive is sufficiently cured. A practical solution would be to require a cure time for sustained load applications beyond the minimum required by the manufacturer. Research by Cook and Konz (2001) test ed twenty anchor systems at 24 hours and at seven days. Almost half of the systems obtained 90% of the seven day strength at 24 hours and the average of all twenty obtained 88% of the seven day strength at 24 hours. ACI 355. 4 11 8.7 has a required test method for cure time at standard temperature in which anchors tested at the manufacturers minimum cure time must achieve 90% of the strength of anchors tested at the minimum cure time plus 24 hours.

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281 It seems reasonable to require that anchors used in sust ained load applications be required to cure for an additional 24 hours beyond the manufacturers minimum cure time before loading or torqueing. Parameters without Adverse Sustained Load Influence The testing criterion for evaluating sustained load influenc e was based on the alpha reduction factor determined from short term testing. If the reduction in strength at any point in time was worse than at two minutes (short term test duration) then the parameter was said to have an adverse effect on the sustained load performance. Most of the following test series have the same or more favorable inservice conditions compared to the baseline but vary by installation condition. It appears that once the adhesive has cured, any reduction in strength due to the inst allation condition can be completely defined by the alphareduction factor from short term testing. As long as the in service conditions are not worse than the baseline, there should not be any further reduction in strength over the service life. TS04 7 0 F service temperature. As can be seen in Figure 6 9 the Influence Ratio of TS04 has a downward trend, or the baseline worsens in comparison to TS04 over time. This can be explained by the fact that polymers will exhibit higher creep displace ments at higher temperatures, especially as the temperature approaches the glass transition temperature. As discussed above, as long as the in service conditions remain the same as the baseline, there should not be any further reduction in strength over t he service life. In the case of TS04, the in service condition is different than the baseline. It appears that a lower inservice temperature is a condition that is more favorable for sustained load performance. With a n Influence R atio of 0.7 3 and a

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282 con fidence level of 100% this parameter is considered not adverse to sustained load performance. TS05 Installation direction (horizontal). Q uality products, e.g., those that have passed ACI 355.411 criteria, that are to be used for horizontal installations must have passed the sensitivity to installation direction test (ACI 355.411 7.18). In this test series the short term load strength of a horizontally installed anchor must be at least 90% of th e strength of an anchor installed in the downward direction. If a product passes this test then installation direction can be considered to not affect the short term strength. Once the adhesive has cured, if the only difference between and anchor installed horizontally to one installed in the downward direction is orientation (i.e., same concrete, moisture condition, temperature, etc.) then the application of sustained load should reasonably have the same effect for both conditions. Due to the discussion above, the Influence R atio of 0.9 3 and confidence level near 80%, this parameter is considered not adverse to sustained load performance. TS06 Installation direction (vertical). The sensitivity to installation direction test (ACI 355.411 7.18) discusse d above also tests for anchors installed vertically. It is believed that vertical installation does not adversely affect the sustained load performance for the same reasons discussed above for horizontal installation (TS05). Due to the discussion above, t he Influence R atio of 0.86 and confidence level near 90%, this parameter is considered not adverse to sustained load performance. TS07 Moisture at installation While moisture at installation created a reduction in short term bond strength ( = 0.82), t he sustained load performance was no worse

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283 than the short term reduction. This can be explained by the fact that the concrete began to dry after installation and eventually dried out in the 110F chamber and the subsequent in service conditions were the s ame as the baseline. With a n Influence R atio of 0.61 and a confidence level of 99% this parameter is considered not adverse to sustained load performance. TS08 Moisture in service. While the Influence R atio is greater that 1 ( 1.02 ), the experimental line and the baseline appear to be the same line within scatter of that data ( Figure H 12) The Monte Carlo simulation indicates that with a 97 % confidence we can assume that the experimental value is above the design value and therefore this parameter is considered not adverse to sustained load performance. TS09 Reduced hole cleaning. While reduced hole cleaning created a reduction in short term bond strength ( = 0.81), once the adhesive had cured, the reduction in adhesion due to the presence of dust on the sides of the borehole could be accounted for in the alpha reduction factor. As time progressed, the amount of adhesion did not change and the reduction in str ength over time was no worse than in the short term. Due to a n Influence R atio of 0.8 4 and confidence level near 80%, this parameter is considered not adverse to sustained load performance. TS10 Installation temperature (MFR minimum/MFR minimum) Currently data is only available for one sustained load stress level (70%MSL) for TS10 and it is not possible to develop an experimental trendline and subsequent Influence R atio and confidence level. However, based on the current results from the 70% stress level tests, it appears that this tests series will not have an adverse effect on the sustained load performance. As discussed earlier and illustrated in Figure 2 5 adhesives respond

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284 to temperature slightly differently, but all show a decrease in bond strength as the temperature increases. As seen in Figure 2 5 it is possible for an anchor installed and tested at a very low temperature to have a higher bond strength than an anchor installed at room temperature and tested at 110F as was the case for the baseline and evidenced by the alpha reduction factor of 1.10. TS11 Installation temperature (MFR minimum/110F ) It appears from the tests conducted at low temperature that as long as the adhesive is installed at a temperature at or above the minimum permitted by the manufacturer that there are no adverse effects under sustained load compared to the baseline This was noticed in TS10 which tested at the manufacturers minimum permitted temperature and in TS11 which tested at 110F. It is definite that the adhesive underwent additional cure over the 24 hours as the specimens were conditioned from the installation temperature to the elevated testing temperature. However, the 0.86 alpha reduction factor indicates that it was not as cured as the baseline that was installed at room temperature. However, the low Influence R atio of 0.7 1 and confidence level of 92 % indicate that this parameter is not adverse to sustained load performance. TS12 DOT concrete mix As discussed earlier, it appears that as long as the inservice conditions are the s ame as the baseline, the alpha reduc tion factor obtained from short term testing for the influence of concrete mix is sufficient to conservatively evaluate the sustained load performance. With a n Influence R atio of 0.53 and a confidence level of 99 % this parameter is considered not adverse to sustained load performance.

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285 TS13 Core drilling. While core drilling created a reduction in short term bond strength ( = 0.73) as time progressed the reduction in strength over time was no worse than in the short term. It is believed that the short term reduction is due to reduced friction along the smoother core drilled hole after loss of adhesion. For the lower stresses experienced in the sustained load tests, the anchor is not as dependent on friction along the sides of the hole. With a n Influence R atio of 0.63 and a confidence level of 100% this parameter is considered not adverse to sustained load performance. TS14 Fly ash It is believed that the addition of fly ash to the concrete mix does not adversely affect the sustained load performance for the same reasons discussed for the DOT mix (TS12). With a n Influence R atio of 0. 70 and a confidence level of 100% this parameter is considered not adverse to sustained load performance. TS15 Blast furna ce slag It is believed that the addition of blast furnace slag to the concrete mix does not adversely affect the sustained load performance for the same reasons discussed for the DOT mix (TS12). With a n Influence R atio of 0.6 2 and a confidence level of 9 7% this parameter is considered not adverse to sustained load performance. TS16 Un confined setup. It was shown earlier that the alpha setup factor of 0.75 is not appropriate for some adhesives. The three adhesives in this study had alpha setup factors in the range of 0.35 to 0.55. As all the data points in the TS16 SvTTF lie above the alpha baseline, and due the low Influence R atio of 0.56 and confidence level of 1 00% it appears that sustained load in unconfined setup is not an adverse condition as long as it is assumed the correct alpha setup factor for the product is used (i.e. 0.37 not 0.75).

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286 Summ ary The following observations on the SvTTF analysis were made: For the SvTTF relationship, a logarithmic model as recommended in AASHTO (2010c) TP 84 10 was considered appropriate Rupture displacements for sustained load tests we re larger (1.33 to 2 times) than those experienced in the short term tests This could affect the practice of projecting sustained load displacements to a limiting displacement from short term tests in ACI 355.4. The short term tests were not included in the final SvTTF curve s du e to earlier than expected failures under high stress level sustained loads and the resulting comparison of SvTTF relationships including and not including the short term test results U nder high stress level sustained load conditions the coupling of cree p strains caused by the sustained load and strains caused by inelastic redistribution of bond stress seem to hasten the failure. AASHTO should modify AASHTO (2010c) TP 8410 to not include short term test results in the determination of the stress versus t ime to failure relationship. The following observations on the sustained load influence analysis were made: The influence of various parameters was evaluated by normalizing the alphabaseline stress by the predicted stress at a given structures lifetime. A parameter was said to not have an adverse influence if the Influence R atio was less than one. A Monte Carlo simulation was conducted to investigate the significance of the Influence R atios by determining the confidence level associated with whether the mean stress for a given parameter wa s greater than the nominal stress evaluated at 15 years. For the parameters tested, it appear ed that once the adhesive had cured, any reduction in strength due to the installation condition c ould be completely defined by the alphareduction f actor from short term testing. Only elevated service temperature and cure time were identified as having an adverse effect on the sustained load performance of adhesive anchors. For elevated service temperature, a modification factor is not recommended f or an anchor exposed to 120F for a very small percentage of its service life (total of 1 to 5 years) A modification factor should only be considered if an anchor is ex posed to temperatures of 120F for significant portions of its service life. If it can be shown that an anchor would be expected to be at or above 120F for significant portions of its service life, it is recommended that the adhesive anchor

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287 system be tested and evaluated for Temperature Category B (ACI 355.4 .5) at a temperature equal to or greater than its highest service temperature. F or the influence of cure time, i t seems reasonable to require that anchors used in sustained load applications be required to cure for an additional 24 hours beyond the manufacturers minimum cure time before loading or torqueing

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288 Table 6 1 Expected failure stress level at five minute load duration for baseline tests with short term tests excluded in the SvTTF projection Test series Expected f ailure s tress l evel at 5 m inute l oad d uration (%MSL) TS01A 78 TS01B 79 TS01C 80 TS02A 71 TS02B 88 TS02C 76 A combined 75 B combined 82 C combined 78 Table 6 2 Peak displacement data for short term (ST) and longterm sustained load (LT) tests for UF baselines Test s eries ST mean (in) ST CoV LT me a n (in) LT CoV Ratio LT/ST Baseline A 0.043 0.09 0.05 9 0.15 1. 4 Baseline B 0.051 0.08 0.100 0.26 2.0 Baseline C 0.046 0.11 0.102 0.29 2.2 Table 6 3 Displacement data at loss of adhesion per ACI 355.411 for short term (ST) tests and peak displacement data for long term sustained load (LT) tests for UF baselines Test s eries ST mean (in) ST CoV LT mean (in) LT CoV Ratio LT/ST Baseline A 0.042 0.15 0.05 9 0.15 1.4 Baseline B 0.034 0.19 0.100 0.26 3.0 Baseline C 0.035 0.14 0.102 0.29 2.9

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289 Table 6 4 Summary of Influence R atio s and confidence level from Monte Carlo simulation Test s eries Influence Ratio of alpha baseline Influence Ratio of nominal stress Confidence l evel 03B 1.22 0.46 0.86 04B 0.7 3 0.28 1.00 05A 0.93 0.35 0.80 06A 0.86 0.32 0.90 07A 0.61 0.23 0.99 08B 1.02 0.39 0.97 09C 0.8 4 0.32 0.7 8 10A 11A 0.7 1 0.27 0.92 12A 0.53 0.20 0.99 13B 0.63 0.24 1.00 14B 0. 70 0.26 1.00 15A 0.6 2 0.23 0.97 16C 0.56 0.21 1.00 22A 0.9 5 0.36 0.6 9 Note: Confidence level is based on a characteristic value assuming a CoV of 0.15 and an infinite number of tests.

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290 Figure 6 1 Baseline TS01B SvTTF plot with short term tests excluded from the projection Figure 6 2 Baseline TS01B SvTTF plot with short term tests includ ed in the projection

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291 Figure 6 3 Ratio of sustained load test failure displacements to short term test failure displacements for UF baselines Figure 6 4 Failure displacement versus time to failure for all three UF baseline tests

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292 Figure 6 5 Failure displacement versus %MSL for all three UF baseline tests Figure 6 6 Combined baseline SvTTF for adhesive A normalized by the average bond stress of the short term tests from UF and US

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293 Figure 6 7 Combined baseline SvTTF for adhesive B normalized by the average bond stress of the short term tests from UF and US Figure 6 8 Combined baseline SvTTF for adhesive C normalized by the average bond stress of the short term tests from UF and US

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294 Figure 6 9 Influence R atio of the alphabaseline stress at various lifetimes Figure 6 10. Influence R atio of alphabaseline stress at 15 years exposure to elevated temperature (75 years)

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295 Figure 6 11. Influence R atio of alphabaseline stress at various lifetimes with the alphareduction factor limited to a maximum value of 1 Figure 6 12. Influence R atio of alphabaseline stress at 15 years exposure to elevated temperature (75 years) with the alphareduction factor limited to a maximum value of 1

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296 Figure 6 13. I nfluence R atio of nominal stress at 15 years exposure to elevated temperature (75 years) with the alphareduction factor limited to a maximum value of 1 and assuming a CoV of 0.15 Figure 6 14. Limitation of method 1

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297 Figure 6 15. Results of Monte Carlo simulation on the Influence Ratio of the nominal stress with alpha reduction factors limited to a maximum value of 1 Figure 6 16. Confidence level that the Influence Ratio of the nominal stress is less than 1 at 15 years exposure to elevated temperature (75 years)

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298 CHAPTER 7 VISCOELASTIC STUDY O F ADHESIVE ANCHORS This chapter presents a study into the viscoelastic behavior of adhesive anchors using an incremental load rate short term test procedure and a finite element investigation. Incremental Load Rate Investigation As discussed earlier, in an incremental load rate test, adhesive anchors wil l continue to displace as a load is held constant due to their viscoelastic nature. This displacement rate was observed to increase as the load level was increased. If the material was purely elastic, the displacement would have remained constant while t he load was held constant. A sample load versus displacement plot for an incremental load rate test on adhesive B is presented in Figure 7 1 It can be seen that the displacement increases as the load level increases for each two minute step. The three adhesives on this project along with two other adhesive anchor systems (adhesives D and E) were subjected to incremental load rate tests (two tests per adhesive). Adhesive D was a mercaptin/amine blend epoxy with talc filler and adhesive E was a hybrid with methacrylate hardener and quartz filler with cementitious material. Four load steps (approximately 50%, 60%, 75%, and 85% of MSL) were used and the load was maintained by a hand pump for two minutes. Several anchors failed before or during the 85% MSL load step. The average displacement rate was calculated for each load step and is plotted versus stress level in Figure 7 2 A linear equation was used to model the trend for all adhesives While this might not be the exact mathematical model, the coefficient of determination (R2) valu es (0.71 0.84) for most adhesives indicate a relatively good fit and confirm an upward trend in

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299 the data as the stress level is increased. Adhesive C had a R2 value of 0. 26 due to scatter at the 85% MSL level Finite Element Investigation An investigation of viscoelastic timedependent effects on the stress distribution of adhesive anchors was conducted using the ADINA finite element software. The finiteelement axisymmetric model ( Figure 7 3 ) made use of symmetry and was 12 wide by 12 tall. The model was restrained in the vertical direction along the top of the confining plate and bottom of the model and in the radial direction along and sides. A total of 3012 eight node axisymmetric elements were used (555 steel bolt elements, 48 steel confining plate elements, 1449 concrete elements, and 960 adhesive elements). The adhesive was divided into two regions ( Figure 7 4 ), an outer ring one element wide at the interface with the concrete (138 elements) and an inner portion that was three elements wide plus portions between the threads (822 elements). The anchor ex tended 1 above the surface of the concrete to ensure that t he stress was effectively distributed within the anchor before engaging the adhesive. Material M odels The steel anchor used an elastic material model (E = 29, 000 ksi, = 0.30) which included the threads and approximated a 5/8 11 UNC threaded rod. The 5/8 thick by 8 diameter steel confining plate with a 1- center hole used the same elastic material model as the bolt. The concrete used an elastic material model (E = 3, 605 ksi, = 0.15) and m easured 12 by 12. The adhesive made use of three material models, a viscoelastic material model and a plastic bilinear material model with and without a maximum allowable effective plastic strain. The viscoelastic model (referred to as

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300 element V) included test data for the shear modulus (G) and the bulk modulus (K) ( Table 7 1 ) for adhesive B at 110F. The plastic bilinear material model (referred to as element P) for the adhesive was characterized as (E = 987 ksi, = 0.4, fy = 6 ksi). A maximum allowable effective plastic strain (EPA) of 0.200 was used for the adhesive. The elastic modulus for the plastic bilinear model was calculated by using the shear modulus (G) from Table 7 1 and Poissons ratio at ten seconds by the following equation: = 2 ( 1 + ) Finite E lement A nalysis Since the ADI NA viscoelastic element (V) does not contain a strain limit, the adhesive anchor analysis was conducted with two models. Both models had a one element thick outer ring of adhesive using the plastic bilinear element with the maximum strain limit ( referred to as element EPA). The first model (referred to herein as P EPA) used an elastic perfectly plastic element (P) for the remainder of the adhesive. The second model (referred to as V EPA) used the viscoelastic element (V) for the reminder of the adhesive. Both models simulated an ASTM E488 test procedure in which the load was applied at a constant load rate up to two minutes. This was simulated by applying the load over 60 2second time steps up to 120 seconds. The V EPA model continued the analysis with progressively larger time steps according to the schedule listed in Table 7 2 As the behavior of the P EPA model did not change with time, the P EPA analysis terminated at 120 seconds.

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301 P EPA M odel Figure 7 5 presents the shear stress distribution along the depth of the hole evaluated at the hole diameter for the P EPA model. The total short term load supported by the anchor in the analysis was 21.6 kips and is referred to as STL for the finite element analysis. It can be seen that below 40% STL, the stress distr ibution approximates a hyperbolic tangent function. As the load is increased, the stress is redistributed further into the hole and approaches a uniform bond stress at 100% STL. V EPA M odel Figure 7 6 through Figure 7 9 show the shear stress distribution along the depth of the hole evaluated at the hole diameter for the P EPA and VEPA models at 95% STL, 80% STL, 60% STL, and 40% STL respectively Also shown is how the V EPA model redistributes stress over time with curves for 2 minutes, 1 day, 10 days, 100 days, and 1 year It can be seen that for the higher load levels, a model w ith viscoelastic properties subjects longer portions of the hole to higher shear stresses than an elastic plastic model. This results in the upper half of the hole for the 95% STL case and the upper third of the hole for the 80% STL case. At lower loads, the V EPA model approaches the same stress distribution as the P EPA model. At 40% STL, the shear stress distribution for the P EPA and VEPA were essentially the same at two minutes It can further be seen that over time, the V EPA model will redistrib ute the stress deeper into the hole as the material softens as illustrated in Figure 7 6 to Figure 7 9 For the 95% STL case, the upper half of the hole remains stressed higher than predicted by the P EPA model for the first 100 days and approaches a uniform stress

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302 distribution at a year. For the 80% STL case, the upper portion of the hole is stressed less than predicted by the P EPA model after about 10 days. Summary Based on the incremental load tests and the results presented in Figure 7 2 two epoxies (adhesives B and D) exhibit a significant increase in displacement rate at higher stress levels. One epoxy (adhesive C) and the vinyl ester (adhesive A) exhibit ed an increase in displacement rate, but not as pronounced as the other two epoxies. T he hybrid (adhesive E) only exhibit ed a slight increase in displacement rate at higher load steps. This appears to validate the higher displacement rates of epoxies (and vinyl esters) at high stress levels due t o their viscoelastic properties The finite element analysis was limited by the material models available in ADINA. As the viscoelastic model did not contain failure criteria, a two layer model for the adhesive was implemented which included a viscoelastic model for the majority of the a dhesive surrounded by an elastic plastic model with a strain limit at the interface with the concrete. The finite element model used in the McVay et al. (1996) study which used an elastoplastic Sandler DiMaggio constitutive model contained failure criter ia but did not include viscoelastic behavior. The results just prior to and at failure therefore are different between this model and the McVay et al. (1996) model. However, t his study was interested in evaluating the effects of the viscoelastic properties of the adhesive on the stress distribution along the anchor prior to failure. This was achieved by comparing the V EPA model to the P EPA which did not include viscoelastic effects. The finite element analysis indicated that:

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303 A viscoelastic model predic t ed higher shear stresses in the upper portions of the hole as compared to an elastic plastic model for loads greater than 40% STL. The shear stress distribution predicted by the viscoelastic model and the elastic plastic model were essentially the same at the 40% STL condition. Over time, the stresses predicted from a viscoelastic model are redistributed further into the hole and approach a uniform stress distribution. For very high loads, the stress near the top of the hole will remain higher than that pr edicted from the elastic plastic model for a longer time than at lower load levels (100 days at 95% STL and 10 days at 80% STL). The results of the finite element study validated the exclusion of short term tests from the SvTTF graphs since the study indicated that under high stress level sustained load conditions the coupling of creep strains caused by the sustained load and strains caused by inelastic redistribution of bond stress seem to hasten the failure. Further investigation with a finite element material model that incorporates viscoelastic properties along with failure criteria could be beneficial to better understand the behavior at failure.

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304 Table 7 1 Shear modulus and bulk m odulus values for viscoelastic model Time (sec) Shear m odulus (G) (ksi) Bulk m odulus (K) (ksi) 10 353 1646 100 317 1481 1000 266 1242 10000 207 964 100000 118 553 1000000 46 217 10000000 14.8 69.1 100000000 4.8 22.6 1000000000 2.5 11.8 10000000000 2.3 10.8 Table 7 2 Time step schedule for finiteelement analysis Number of time steps Length of time step (s) Approximate e nd of s eries 60 2 2 min 108 10 20 min 24 100 1 hour 8 1000 3 hours 9 10000 28 days 9 100000 12 days 9 1000000 116 years 9 10000000 3.2 years 9 100000000 32 years 9 1000000000 317 years

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305 Figure 7 1 Incremental load rate short term test on adhesive B Figure 7 2 Displacement rate versus stress level for various adhesive anchor systems

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306 Figure 7 3 Finite element mesh Figure 7 4 Enlarged view of finite element mesh

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307 Figure 7 5 Shear stress distribution at various load levels for P EPA model Figure 7 6 Shear stress distribution at 95% STL for P EPA and VEPA models

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308 Figure 7 7 Shear stress distribution at 80% STL for P EPA and VEPA models Figure 7 8 Shear stress distribution at 60% STL for P EPA and VEPA models

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309 Figure 7 9 Shear stress distribution at 40% STL for P EPA and VEPA models

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310 CHAPTER 8 CORRELATION WITH ADHESIVE ALONE TESTS T he analysis and results of the adhesive alone testing program conducted at the University of Florida to investigate the isolated sustained load and short term creep behavior of the adhesive alone under NCHRP project 0437 can be found in Appendix I It is presented as an a ppendix as it was written primarily by Changhua Liu. The purpose of this chapter is to determine if adhesive alone testing can predict the sustained load behavior of adhesive anchors in concrete. Mechanics of Dogbones and Adhesive Anchor Systems The dogbone and adhesive anchor tests measure different strains. Principal tensile strains will be used for comparison between the two test specimens. Strain in Dogbone Specimens The dogbones were loaded in pure tension and due to the orientation of loading the strain gages directly measured the principal tensile strains. Strain in Adhesive Anchor System The strain measured in the anchor pullout tests wa s an approximation of shear strain calculated as the arctangent of the anchor displacement over the annular gap ( Figure 8 1 ). This wa s not a direct measurement of adhesive strain but rather determined from the total anchor displacement which wa s comprised of the strain in the adhesive as well as the strain in the anchor, and slippage of the adhesive/anchor plug within the hole. The finite element analysis software ADINA and Mohrs circle w ere used to evaluate the stains in the adhesive anchor system under short term load. The P EPA model (described earlier) was used to compare the s trains at failure for the short term

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311 as the creep effects accounted for in the V EPA model are not necessary for a short term test. Returning to the axisymmetric finite element model described earlier, the adhesive is in a plane strain condition as it is restrained in the tangential direction. From Mohrs circle for plane strain we know that the maximum shear strain ( ) is the diameter of the circle which is also the absolute value of the difference between the maximum and minimum principal strains The finite element model verified that the principal compressive and tensile strains were essentially equal in magnitude but opposite in sign along the depth of the hole evaluated at both the anchor diameter and the hole diameter. This indicates that the maximum principal tensile strains were half of the shear strains. Figure 8 2 plots the displacement profile of the ad hesive near the top of the hole across the annular gap. It can be seen that the analyt ical model predicts that displacement of the adhesive is very small at the hole diameter and increases nonlinearly across the gap with a drastic increase close to the anchor. The approximation of shear strain mentioned earlier which uses the total anchor displacement and the annular gap assumes a linear variation of displacement across the annular gap. This approximation grossly overestimates the shear strain at the hole diameter and underestimates the shear strain at the anchor diameter. The large differ ence observed between the principal tensile strains at the hole diameter and at the anchor diameter shown in Figure 8 3 wa s most likely due to stress concentrations along the threads of the anchor. Note that the strains in Figure 8 3 are plotted on a logarithmic scale due to the different orders of magnitude of the various strains

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312 Comparison of Strains Also illustrated in Figure 8 3 i s the shear strain as determined by the displacement of the anchor and the annular gap which is about 3 0 times larger than the principal tensile strains at the hole diam e ter. T he principal tensile strains along the hole diameter in the finite element model are of the same order of magnitude as those experienced by the dogbones at failure These principal tensile strains can be used as a link between the dogbones and the experimental and analytical anchor results. The shear strai n determined by the anchor displacement and the annular gap in the experimental tests is 90 times larger than the tensile strains experienced by the dogbones. This same shear strain in the analytical model is 30 times larger than the tensile strains exper ienced by the dogbones. It is the authors opinion that this discrepancy is primarily due to slippage of the adhesive/anchor plug in the hole which is measured experimentally but not accounted for in the finite model. The shear strain reported from anch or pullout tests is determined from the anchor displacement and the annular gap because it is simple to measure. It is not practical to measure the shear strain (or adhesive displacement) at discrete points across the 1/16 thick annular gap. While not practical it is possible to measure the slippage of the anchor within the hole. This can be done by drilling a hole from the bottom of the concrete test specimen to expose the bottom of the anchor in order to measure its slippage. Sustained L oad Test Resu lts C reep compliance curves for the anchor pullout tests were generated and compared the dogbone specimens. Figure 8 4 to Figure 8 6 present the creep

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313 compliance comparisons for the three adhesives. Only the compliance comparison for adhesive C show ed a similar trend between the two sets of tests, although separated by almost two orders of magnitude. Adhesives A and B did not provide good comparisons. Stress versus Time to Failure Results for Anchor Pullout and Dogbone Tests Figu re 8 7 to Figure 8 9 present a comparison of the SvTTF relationships determined from the combined anchor pullout tests and the dogbone tests. The SvTTF curves for the dogbones are presented in Appendix H (series 21 and 22). While the dogbone tests did a very poor job predicting the SvTTF results for adhesive B and C, they did a better job for adhesiv e A. This is possibly due to the poor adhesion of adhesive A. Adhesive anchor systems with better adhesion can develop more friction along the sides of the hole prior to failure as the adhesive/anchor plug will have pieces of concrete attached. Dogbone specimens do not have this additional frictional resistance. Summary The following observations were made about the correlation between adhesive anchor tests and adhesive alone tests: T he shear strain determined experimentally from the anchor displacement and annular gap wa s an approximation and differ ed from the actual shear strain which varie d along the thickness of the annular gap T he shear strain ( or displacement ) of the adhesive along the thickness of the annular gap wa s not practical to measure experimentally The principal tensile strains in the dogbone specimens were similar to the principal tensile strains along the side of the hole in the finite element results. As it wa s not possible to measure these principal tensile strains in the adhesiv e anchor tests experimentally, the shear strain calculated between the anchor displacement and the annular gap was used to link the experimental results with the finite element results. The finite element model and the experimental results varied by a fac tor of 3.

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314 The discrepancy between the shear strain calculated from the anchor displacement and the annular gap determined by the finite element model and measured experimentally was due to the finite element model not accounting for the slippage of the anc hor in the hole. Currently, it is not practical to make a direct comparison of experimentally measured strains between dogbones and adhesive anchors. Creep compliance did not provide a good correlation across adhesives between sustained load tests conducted on dogbones and adhesive anchors. The stress versus time to failure curves between the adhesive alone and adhesive anchor tests did not provide a good correlation for all adhesives tested. The dogbone specimens did a better job predicting the SvTTF relat ionship of the adhesive anchors for adhesive A. This wa s probably due to the poor adhesion of adhesive A. Adhesive anchor systems with better adhesion can develop more friction along the sides of the hole prior to failure as the adhesive/anchor plug wi ll have pieces of concrete attached. Dogbone specimens do not have this additional frictional resistance.

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315 Figure 8 1 Shear strain approximation in anchor tests Figure 8 2 Displacement of the adhesive near the top of the hole radially across the annular gap

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316 Figure 8 3 Distribution of strains along the depth of the hole as determined by finite element analysis Figure 8 4 Creep compliance comparison between dogbone and anchor tests for adhesive A (courtesy of Changhua Liu)

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317 Figure 8 5 Creep compliance comparison between dogbone and anchor tests for adhesive B (courtesy of Changhua Liu) Figure 8 6 Creep compliance comparison between dogbone and anchor tests for adhesive C (courtesy of Changhua Liu)

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318 Figure 8 7 SvTTF comparison between anchor pullout tests and dogbone tests for adhesive A Figure 8 8 SvTTF comparison between anchor pullout tests and dogbone tests for adhesive B

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319 Figure 8 9 SvTTF comparison between anchor pullout tests and dogbone tests for adhesive C

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320 CHAPTER 9 EARLY AGE CONCRETE TEST RESULTS This chapter presents the results of the investigation of the effects of ear ly age concrete on the short term confined test bond strength of adhesive anchors. The tests on the effects of early age concrete (TS17) are identified as DDD A ST R, where: DDD: Day of testing (D04, D07, D14, D21, D28) A: A dhesive type (A, B, or C) ST: Signifies short term test R: Test repetition number (1 5) Short term Test Results The short term test load versus displacement and stress versus displacement results for the early age confined test investigation are presented in Appendix J. The results are summarized in Figure 9 1 which normalizes the results by the 28 day bond strength. It appears that on the basis of confined test bondstrength alone, adhesive A (vinyl ester) did not show any significant increase after 14 days (102% of 28 day strength at 14 days), and adhesive B and C (epoxies) did not show any significant incre ase after 7 days (104% and 93% of 28 days strength at 7 days respectively). Discussion of Anomalies Several of the anchors for adhesive A failed not with a strength type failure but rather a stiffness type failure. In these cases, f ailure was defined as t he point when the loaddisplacement curve dropped below a stiffness of 28.6 kip/in (5 kN/mm) as discussed earlier and illustrated in Figure 4 46 Test samples D21C S T 4 ( Figure 9 2 ) D28 C ST 3, and D28C ST 5 all pulled out at very low bond stresses. The anchors were removed from their holes for

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321 investigation. It was noticed that the adhesive had not completely cured as it was still tacky with a dark gray glossy color indicating an improper ratio of the hardener and resin. Per NTSB (2007), excess hardener is evidenced by a pliable consistency and a decrease in bond strength. T he anchors of this adhesive that failed at higher bond stresses were also removed and exhibited hard fully cured adhesive with a flat whitishgray color ( Figure 9 3 ). All the holes were cleaned identically per the MPII at the same time. The same adhesive tube was used for all five repetitions for a given test day. The anchors for day 28 used a differen t tube than those for day 21. These three samples were considered anomalies and were not included in the determination of the mean. Of the three adhesives used in this project, Adhesive C was significantly more difficult to dispense by hand during install ation. The difficulty in dispensing indicated that at least one of the components was very viscous. If one component was significantly more viscous than the other, it is possible that there could have been an abundance of the other component, which flowed more easily. This is a possible explanation for why these samples were not completely cured. Temperature and Humidity The four Sensiron temperature and humidity sensors that were cast in the control slab were destroyed in the casting process. Therefore the two 9 long PCV pipes with PVDF filters on the embedded ends in each slab were used for temperature and humidity monitoring. During testing, two sensors were placed in the two pipes of the control slab and left for the duration of the monthlong tes ting period. The remaining two sensors were placed in the test slab of the anchors being tested.

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322 The temperature readings from the control slab and the individual testing slabs were within a 2F agreement with each during the testing program. The internal concrete temperature for both slabs followed the daily temperature fluctuation of the laboratory and were within 4F (and less than) the ambient temperature of the laboratory. The only exception was on day 4 when the concrete internal temperature was 7 F below the ambient temperature of the laboratory. The temperature readings are presented in Table 9 1 The Sensiron sensors in the control slabs reported a consistent 100% relative humidity (RH) reading for the entire month. For testing, separate slabs were used for a given day and then discarded. The RH readings from the sensors in the test slabs were all greater than 96%. It seems reasonable that since al l the concrete slabs were cast at the same time and kept together prior to testing that there would be a consistency in RH readings with each other. However, when the sensors were switched between slabs, the RH reading would be less than the previous slab and would show a sharp increase and take several days to stabilize. Initially, the slabs would be changed out on Monday morning, the anchors installed on Thursday, and tested on Friday. Except for day 14, this did not provide sufficient time for the readings to stabilize prior to testing. In response to this, the slabs for day 28 were changed out on the Friday before testing providing a full week of readings and the RH readings began to stabilize (within the daily fluctuation of the ambient RH) on the t esting day. The RH data is presented in Table 9 2 It does not seem reasonable that the RH at day 21 should be higher than at day 14 as the RH in concrete should dec rease over time as hydration progresses and

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323 moisture is lost to evaporation at the surface. The datasheet for the sensors indicate that they are accurate to 4%RH in the range of 90 to 100% RH. Based on control slab RH readings of 100% and the limitations of the sensors (tolerance and time to stabilize) the only definitive conclusion that can be drawn from the RH data is that the RH was in the range of 96% to 100%. Initial Surface Absorption The ISAT records samples at 10 minutes, 30 minutes, and 60 minutes after applying the water. For adhesive anchors, the 10 minute reading is the most relevant reading as the 30 minute and 60 minutes measure the surface absorption of essentially saturated concrete which is not a common condition for most adhesive anchor installations. Table 9 3 presents the 10 minute sample data from the ISAT program as well as the relative humidity recorded during testing. The data is based on three repetitions (one repetition for day three of the formed surface). In order to better evaluate trends, ISAT testing was conducted up to 35 days after casting. Figure 9 4 presents the ISAT data for over the 35 day testing period for the top formed surface and the sides of the hole. Initially the surface absorption of the top formed surface and the sides of the hole showed similar rates. The top formed surface drasti cally increased in surface absorption over the first two weeks and then leveled off (within the scatter of the data). For this concrete specimen, as the concrete dehydrated, the top surface increased in absorption but reached equilibrium with the environm ent after two weeks. The surface absorption of the sides of the hole remained fairly consistent over the first two weeks as the moisture several inches from the surface was not as easily lost to the environment.

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324 Eventually after two weeks, the surface absorption began to increase as the process of dehydration slowly dried out deeper and deeper portions of the concrete specimen. Initial surface absorption is indirectly a measure of internal moisture. As the internal moisture is high, the surface absorption will be lower. Without accurate internal humidity data, the initial surface absorption data is the only indication available on the relative measure of internal moisture. Based on these tests it appears that there is a threshold of internal moisture, i n which for installations above this value, the bond stress is not affected. Hardness The rebound and indention hammers used to determine hardness generated similar trends of increasing hardness over time. Both hammers had conversion charts to predict the 6 cube compressive strength which the indention hammer had good agreement for the first 14 days then underestimated the strength. The rebound hammer consistently overestimated the concrete strength. The rebound hammer produced values that were 20% to 45% higher than the indention hammer. Figure 9 5 presents the data for the hardness tests as well as the compression and split tensile tests. All show similar trends of increasing value over time. Summary The following observations on the effect of early age concrete on the short term bond strength wer e made: It appears that on the basis of confined test bondstrength alone, adhesive A (vinyl ester) d id not show any significant increase after 14 days (102% of 28 day strength at 14 days) and adhesive B and C (epoxies) did not show any significant increase after 7 days (104% and 93% of 28 days strength at 7 days respectively) Adhesive C exhibited a few anomalies in bond strength in which post failure investigation indicated that they were not properly cured. A possible explanation is

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325 that this improper curing wa s due to the difficulty in dispensing the adhesive and the improper proportioning due to differences in viscosity in the two components. Internal concrete temperature fluctuated with daily ambient temperature and was determined as not having an ef fect on the early age bond strength Due to instrumentation difficulties and tolerance the internal humidity data was not sufficient to make a correlation with early age bond strength. I nitial surface absorption tests (on top surface and side of hole) prov ided an indirect measure of internal moisture. The initial surface absorption of the sides of the hole remained relatively constant for the first two weeks and then increased thereafter. These tests indicated that there is a threshold of internal moistur e, in which for installations above this value the bond stress wa s not affected. Concrete hardness measurements from the indention hammer and rebound hammer as well as the split tensile and compression strength results produced trends similar to the trend in the short term bond strengt h. It is the authors conclusion that the predominan t contributor to lower bond strengths in early age concrete is due to the higher moisture content in early age concrete. The short term tests on moisture at installation (TS 07) resulted in alpha reduction factors for adhesives A, B, and C of 0.82, 0.94, and 0.92 respectively indicating that moisture does affect the short term bond strength. It is interesting to note that the bond strengths for adhesive A at 4 and 7 days norma lized by its 28 day strength are 0.77 and 0.83 which is very close to the alphareduction factor for moisture at installation. The 7 day bond strength for adhesive C normalized by its 28 day value is 0.92 which is identical to the alpha reduction factor f or moisture at installation. While the trends for concrete split tensile and compression strengths exhibited a similar trend to the increase in bond strength, the author does not believe that these are the primary causes for bond strength increase. Based on Cook and Konz (2001) concrete strength was shown to not have a consistent relationship with bond strength

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326 ( Figure 2 3 ) however their study was limited to concrete strengths in the range of 4200 to 9000 psi. According to Eligehausen et al. (2006b) any increase in bond strength due to an increase in concrete strength can be offset by reduced roughness in the sides of the hole. Both measures of hardness showed similar trends with bondstrength. This could be an indicator of roughness as harder concrete can lead to smoother holes which reduce the mechanical i nterlock between the adhesive and the side of the hole. This could have been confirmed with the roughness investigation, but was not possible during this project.

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327 Table 9 1 Temperature readings for the e arly age concrete evaluation Test d ay Control s lab (F) Test s lab (F) Ambient (F) 4 78 77 84 7 74 72 75 14 72 70 74 21 73 73 75 28 77 76 79 Table 9 2 Relative humidity readings for the early age concrete evaluation Test d ay Test s lab r elative h umidity (F) Ambient r elative h umidity (F) Comment 4 98.6 40 RH not stabilized 7 96.2 38 RH not stabilized 14 99.4 49 21 99.8 52 RH not stabilized 28 99.3 53 Table 9 3 ISAT 10 minute sample data and relative humidity for sides of hole and formed surface Age (days) Sides of h ole (ml/m 2 s) Formed s urface (ml/m 2 s) Ambient r elative h umidity (%) 3 0.036 0.030* -6 0.031 0.047 39 13 0.028 0.097 54 20 0.043 0.094 65 27 0.059 0.080 59 35 0.074 0.092 46 Note: All ISAT data is based on an average of three repetitions except for the day 3 sample for the formed surface Table 9 4 Rebound and indention hammer results Age (days) Rebound h ammer (psi) Indention h ammer (psi) Ratio r ebound/ i ndention 4 3480 2900 1.20 7 4640 3400 1.36 14 4930 3770 1.31 21 5000 3770 1.33 28 5220 3630 1.44

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328 Figure 9 1 Normalized bond stress (by 28 day value) versus concrete age Figure 9 2 D21 C ST 4 showing failure surface of incompletely cured specimen (photo courtesy of author)

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329 Figure 9 3 D21 C ST 5 showing failure surface of fully cured specimen (photo courtesy of author) Figure 9 4 ISAT 10 minute sample data and relative humidity for sides of hole and formed surface

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330 Figure 9 5 Hardness, concrete compression strength, and split tensile strength versus concrete age

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331 CHAPTER 10 CONCLUSIONS AND RECO MMENDATIONS Summary Th e investigation presented in this dissertation was primarily related to the evaluation of the sustained load performance of adhesive anchors in concrete under different installation and inservice conditions using the S tress versus T ime to F ailure approach found in AASHTO (2010c) TP 84 10. In order to evaluate the sensitivity to the different variables, three unique ICCES AC 308 approved adhesive anchor systems were used in a comprehensive series of short term te sts and time to failure sustained load tests The variables investigated are provided in the test matrix shown in Table 3 2 As noted in Table 3 2 most tests performed in the evaluation of sustained load performance were performed at 110F. The results of this research were used to draft recommended standards and specifications for AASHTO pertaining to testing, design, construction, and inspection of adhesive anchors in concrete for transportation structures. The implementation of this investigation of the sustained load performance of adhesive anchors incorporate d several areas of study. These areas are listed below in the order in which they are presented in the chapters of the dissertation and in the following c onclusions and recommendations: Anchor Pullout Testing This area of investigation included confined and unconfined s hort term and sustained load tests. The confined test setup isolated the failure to the adhesive bond surface in order to determine the bond strength. The unconfined test setup allow ed for bond failure with a shallow concrete cone or complete concrete br eakout failure. Short -

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332 term confined anchor pull out tests were used to determine the mean short term bond strength for the baseline condition and each of the investigated parameters. The ratio between a parameters mean short term bond strength and that of the appropriate baseline tests provided a short term reduction value for the parameter (i.e., a factor representing the effect of the parameter under short term loads). Anchor pull out tests were performed under different levels of sustained load until failure occurred. For baseline tests, these were performed at different percentages of the mean short term bond strength of the product. For parameter tests, these were performed at different percentages of the mean short term bond strength multiplied by the appropriate short term reduction value. As a part of the assessment of test results, specimens were cored and split open as well as analyzed with an X ray CT system in an attempt to identify the location of the initial failure surface. Stress versus Time to Failure and Sustained Load Influence The results of the sustained load anchor pullout tests were used to develop a relationship of stress level and resulting timeto failure for baseline conditions and for each of the investigated parameters. The results of these tests are referred to as Stress versus Time to Failure (SvTTF) relationships. Sustained load influence to each parameter was evaluated by comparing the experimentally predicted SvTTF relationship for the parameter to the SvTTF for the baseline multiplied by the strength reduction factor for the parameter. The influence of each parameter was also evaluated using the SvTTF relationships by comparing the experimentally predicted failure stresses with and without the parameter at the time asso ciated with the length of time an AASHTO bridge structure might be exposed to 110F temperature. A similar comparison was made using nominal bond strength

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333 determined by applying ACI 31811 and 355.411 provisions to the SvTTF baseline relationship. A Monte Carlo simulation modeling the slopes and intercepts of the experimental and baseline regression lines was also used to determine the confidence level for the influence of each parameter. Viscoelastic Study of Adhesive Anchors The viscoelastic effects of adhesive anchors were investigated experimentally using an incremental load rate test procedure on three epoxies, one viny l ester, and one hybrid product in which the load was applied in two minute steps The viscoelastic effects were also evaluated a nalytically by means of a finite element analysis. Correlation between Adhesive Anchor Tests and Adhesive Alone Tests The results of an experimental study on the adhesives alone using dogbone specimens and DSR testing were used to investigate their potenti al to predict sustained load adhesive anchor performance. Early Age Concrete Tests Tests were also conducted on the effect of early age concrete on adhesive anchor short term bond strength. Observations and Conclusions The following observations and conclusions can be drawn from this research. Anchor Pullout Testing The results from the unconfined short term tests seem to indicate that the 0.75 ratio of unconfined bond strength to confined bond strength in ACI 355.411 and ACI 318 11 to determine the unconfined bond strength from a series of confined tests might be a significant overestimate of unconfined bond strength. T ests on the three adhesives in this research project produced factors of 0.53, 0.43, and 0.37. Additional verification tests in higher strength concrete were conducted to verify the reduction factor s. These verification tests at 80F and 110F resulted in alpha factors of 0.40 and 0.41 respectively

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334 Several anchors were cored and split open for investigation of the a dhesive failure surface. Two com mon failure modes were observed: loss of adhesion with the concrete ( Figure 5 8 ) and shearing failure of the adhesive at the threads ( Figure 5 9 ) Also observed was that it appeared an adhesive/anchor plug would detach from i ts original location and shift upward in the hole. An x ray CT system wa s used to investigate the location of initial cracking in two adhesive anchor specimens loaded just prior to failure under both short term ( Figure 5 11 and Figure 5 12) and sustained loading ( Figure 5 13 and Figure 5 14) The x ray CT system was unable to discern cracks in the adhesive. A third specimen was loaded well beyond failure to ensure cracking and the system was also unable to discern cracks within the adhesive ( Figure 5 15 and Figure 5 16) Stress versus Time to Failure and Sustained Load Influence Stress versus timeto failure For the SvTTF relationship, a logarithmic model as recommended in AASHTO (2010c) TP 8410 was appropriate. Rupture displacements for sustained load tests we re larger (1.33 to 2 times) than those experienced in the short term tests ( Figure 6 3 ) This could affect the practi ce of projecting sustained load displacements to a limiting displacement from short term tests in ACI 355.4. The short term tests were not included in the final SvTTF curve s due to earlier than expected failures under high stress level sustained loads and the resulting comparison of SvTTF relationships including and not including the short term test results U nder high stress level sustained load conditions the coupling of creep strains caused by the sustained load and strains caused by inelastic redistribution of bond stress seem to hasten the failure. Sustained l oad influence For the parameters tested, it appear ed that once the adhesive had cured, any reduction in strength due to the installation condition c ould be adequately defined by the alpha reduction f actor from short term testing. Only elevated service temperature and cure t ime were identified as having adverse effect s on the sustained load performance of adhesive anchors. Viscoelastic Study of Adhesive Anchors Incremental l oad t ests The incremental load tests indicated that two of the epoxies tested exhibit ed a significant increase in displacement rate at higher stress levels. Another epoxy and a vinyl ester showed an increase in displacement rate, but not as pronounced

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335 as the other two epoxies. A hybrid only showed a slight increase in displacement rate at higher load steps. This appears to validate the higher displacement rates of epoxies (and vinyl esters) at high stress levels ( Figure 7 2 ) due to their viscoelastic properties Finite element analysi s A viscoelastic model predict ed higher shear stresses in the upper portions of the hole as compared to an elastic plastic model for l oads greater than 40% STL. The shear stress distribution predicted by the viscoelastic model and the elastic plastic model were essentially the same at the 40% STL condition ( Figure 7 9 ) Over time, the stresses predicted from a viscoelastic model are redistributed further into the hole and approach a uniform stress distribution ( Figure 7 6 to Figure 7 9 ) For very high loads, the stress near the top of the hole will remain higher than that predicted from the elastic plastic model for a longer time than at lower load levels (100 days at 95% STL ( Figure 7 6 ) and 10 days at 80% STL ( Figure 7 7 ) ). The results of the finite element study validated the exclusion of short term tests from the SvTTF graphs since the study indicated that under high stress level sustained load conditions the coupling of creep strains caused by the sustained load and strains caused by inelastic redistribution of bond stress seem to hasten the failure. Correlation between Adhesive Anchor Tests and Adhesive Alone Tests The shear strain determined experimentally from the anchor displacement and annular gap ( Figure 8 1 ) wa s an approximation and differ ed from the actual shear strain or displacement of the adhesive which varied along the thickness of the annular gap ( Figure 8 2 ) The shear strain or displacement of the adhesive along the thickness of the annular gap wa s not practical to measure experimentally. The principal tensile strains in the dogbone specimens ( Figure 2 22 ) were similar to the principal tensile strains along the side of the hole in the finite element results. As it wa s not possible to measure these principal tensile strains in the adhesive anchor tests experimentally, the shear strain calculated between the anchor displacement and the annular gap was used to link the experimental results with the finite element results. The finite element model and the experimental results varied by a factor of 3. This discrepancy was due to the finite element model not accounting for the slippage of the anchor in the hole. Currently, it is not practical to make a direct comparison of experimentally measured strains between dogbones and adhesive anchors.

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336 Creep compliance curves (strain normalized by stress level versus time) did not provide a good correlation across adhesives between sustained load tests conducted on dogbones and adhesive anchors. The stress versus time to failur e curves between the adhesive alone and adhesive anchor tests did not provide a good correlation for all adhesives tested. The dogbone specimens did a better job predicting the SvTTF relationship of the adhesive anchors for adhesive A ( Figure 8 7 to Figure 8 9 ) This wa s probably due to the poor adhesion of adhesive A. Adhesive anchor systems w ith better adhesion can develop more friction along the sides of the hole prior to failure as the adhesive/anchor plug will have pieces of concrete attached. Dogbone specimens do not have this additional frictional resistance. Early Age Concrete Investi gation O n the basis of confined test bondstrength alone, adhesive A (vinyl ester) did not show any significant increase after 14 days (102% of 28 day strength at 14 days), and adhesive B and C (epoxies) did not show any significant increase after 7 days ( 104% and 93% of 28 days strength at 7 days respectively) ( Figure 9 1 ) Internal concrete temperature was determined to not have an effect on the early age bond strength. I nitial surface absorption tests provided an indirect measure of internal moisture. The initial surface absorption of the sides of the hole remained relatively constant for the first two weeks and then increased thereafter. These tests indicate that there wa s a threshold of internal moisture, in which for installations above this value the bond stress wa s not affected ( Figure 9 4 ) Concrete hardness measurements from the indention hammer and rebound hammer as well as the split tensile and compression strength results produced trends similar to the trend in the short term bond strength ( Figure 9 5 ) The bond strengths for adhesive A at 4 and 7 days normalized by its 28 day strength we re 0.77 and 0.83 which wa s very close to the alphareduction factor for moisture at installation. The 7 day bond strength for adhesi ve C normalized by its 28 day value wa s 0.92 which wa s identical to the alpha reduction factor for moisture at installation. It is the authors conclusion that the predominan t contributor to lower bond strengths in early age concrete wa s due to the higher moisture content in early age concrete. While the trends for concrete split tensile and compression strengths were similar to the trend in the increase in bond strength, the author does not believe that these we re the primary causes for bond strength increase due to the inverse relationship

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337 between concrete strength and hardness as harder concrete leads to smoother holes Recommendations Based on the research performed, the following recommendations are suggested. Anchor Pullout Testing The a lpha setup fact or for the relationship between unconfined to confined bond strength in ACI 355.411 should be adjusted or a test series added to determine this relationship for individual products The results of this research showed that this value can be in the range of 0.35 to 0.55 and is significantly less than t he value of 0.75 currently assumed in ACI 355.411. X ray CT scanning techniques could be further investigated to attempt to determine the location o f first cracking and the failure surface in adhesive anchor s under load prior to failure. Stress versus Time to Failure AASHTO should modify AASHTO (2010c) TP 8410 to not include short term test results in the determinati on of the stress versus timeto failure relationship. Additional sustained load testing at hi gh stress levels could be performed to better identify the stress versus time to relationship within time to failures of a few hours. Sustained Load Influence For elevated service temperature, a modification factor is not recommended for an anchor exposed to 120F for a very small percentage of its service life (total of 1 to 5 years). A modification factor should only be considered if an anchor is exposed to temperatures of 120F for significant portions of i ts service life. If it can be shown that an anc hor would be expected to be at or above 120F for significant portions of its service life, it is recommended that the adhesive anchor system be tested and evaluated for Temperature Category B (ACI 355.4 .5) at a temperature equal to or greater than its highest service temperature. For the influence of cure time, it seems reasonable to require that anchors used in sustained load applications be required to cure for an additional 24 hours beyond the manufacturers minimum cure time before loading or torqueing. Adhesive anchor sustained load tests at room temperature at various adhesive cure times could be performed to evaluate the influence of cure time on the sustained load performance.

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338 Viscoelastic Study of Adhesive Anchors Further investigation with a f inite element material model that incorporates viscoelastic properties along with failure criteria could be beneficial to better understand the behavior of adhesive anchors undergoing failure from sustained loads Early age Concrete Investigation The hole roughness could be investigated for possible influence on the bond strength of adhesive anchors in early age concrete.

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339 APPENDIX A CONCRETE MIX DESIGNS Table A 1 Concrete mixes used for each test Test or t est s eries Lab Mix 01 A 88 1 UF A 01 A 88 2 UF A 01 A 87 3 UF A 01 A 76 4 UF F 01 A 68 5 UF F 01 A 57 6 UF F 01 A 57 7 UF A 01 A 57 8 UF A 01 A 57 9 UF A 01 A 46 10 UF B 01 A 46 11 UF B 01 A 46 12 UF B 01 A 36 13 UF E 01 A 36 14 UF E 01 A 36 15 UF E 01 B 81 1 UF B 01 B 81 2 UF B 01 B 75 3 UF B 01 B 73 4 UF G 01 B 72 5 UF G 01 B 70 6 UF B 01 B 70 7 UF B 01 B 68 8 UF G 01 B 67 9 UF B 01 B 56 10 UF A 01 B 55 11 UF A 01 B 53 12 UF A 01 B 45 13 UF B 01 B 45 14 UF B 01 B 44 15 UF B 01 C 80 1 UF B 01 C 79 2 UF B 01 C 72 3 UF F 01 C 72 4 UF F 01 C 72 5 UF F 01 C 71 6 UF B 01 C 70 7 UF C

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340 Table A 1. Continued. Test or t est s eries Lab Mix 01 C 68 8 UF C 01 C 59 9 UF C 01 C 52 10 UF A 01 C 50 11 UF A 01 C 47 12 UF A 01 C 44 13 UF A 01 C 44 14 UF A 01 C 44 15 UF A 02 A US A 02 B US A 02 C US A 03 B US B 04 B US B 05 A US A 06 A US A 07 A UF C 08 B US B 09 C UF D 10 A US B 11 B US B 12 A UF J 13 B UF G 14 B UF H 15 A UF I 16 C 73 1 UF C 16 C 72 2 UF G 16 C 69 3 UF C 16 C 71 4 UF F 16 C 69 5 UF F 16 C 69 6 UF F

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341 Figure A 1 Concrete mix design laboratory worksheet for UF:A 1

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342 Figure A 2 Concrete mix design laboratory worksheet for UF:A 2

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343 Figure A 3 Concrete mix design laboratory worksheet for UF:A 3

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344 Fig ure A 4 Concrete mix design laboratory worksheet for UF:B 1

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345 Figure A 5 Concrete mix design laboratory worksheet for UF:B 2

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346 Figure A 6 Concrete mix design laboratory worksheet for UF:B 3

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347 Figure A 7 Concrete mix design laboratory worksheet for UF:C 1

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348 Figure A 8 Concrete mix design laboratory worksheet for UF:C 2

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349 Figure A 9 Concrete mix design laboratory worksheet for UF:C 3

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350 Figure A 10. Concrete mix design laboratory worksheet for UF:D 1

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351 Figure A 11. Concrete mix design laboratory worksheet for UF:D 2

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352 Figure A 12. Concrete mix design laboratory worksheet for UF:D 3

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353 Figure A 13. Concrete mix design laboratory worksheet for UF:E 1

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354 Figure A 14. Concrete mix design laboratory worksheet for UF:E 2

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355 Figure A 15. Concrete mix design laboratory worksheet for UF:E 3

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356 Figure A 16. Concrete mix design laboratory worksheet for UF:F 1

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357 Figure A 17. Concrete mix design laboratory worksheet for UF:F 2

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358 Figure A 18. Concrete mix design laboratory worksheet for UF:F 3

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359 Figure A 19. Concrete mix design laboratory worksheet for UF:G 1

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360 Figure A 20. Concrete mix design laboratory worksheet for UF:G 2

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361 Figure A 21. Concrete mix design laboratory worksheet for UF:G 3

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362 Figure A 22. Concrete mix design laboratory worksheet for UF:H 1

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363 Figure A 23. Concrete mix design laboratory worksheet for UF:H 2

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364 Figure A 24. Concrete mix design laboratory worksheet for UF:H 3

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365 Figure A 25. Concrete mix design laboratory worksheet for UF:I 1

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366 Figure A 26. Concrete mix design laboratory worksheet for UF:I 2

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367 Figure A 27. Concrete mix design laboratory worksheet for UF:I 3

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368 Figure A 28. Florida Rock concrete mix design for mix UF:G (page 1 of 2)

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369 Figure A 29. Florida Rock concrete mix design for mix UF:G (page 2 of 2)

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370 Table A 2 Concrete mix design for mix US:A Material Amount (kg/m 3 ) Amount (lbs/CY) Cement: CEM I 32,5 R 240 405 Aggregate (according to EN 12620): 0 2 mm 797 1343 2 8 mm 502 846 8 16 mm 742 1251 Water (aggregate moisture + water): Total 173 291 w/c: 0.718 Table A 3 Concrete mix design for mix US:B Material Amount (kg/m 3 ) Amount (lbs/CY) Cement: CEM I 32,5 R 239 403 Aggregate (according to EN 12620): 0 2 mm 785 1323 2 8 mm 504 850 8 16 mm 747 1259 Water (aggregate moisture + water): Total 180 303 w/c: 0.753

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371 APPENDIX B ANCHOR PULLOUT TESTS UNIVERSITY OF STUTTG ART This appendix presents the test program conducted under NCHRP project 0437 by Ronald Blochwitz at the University of Stuttgart Intsitt fr Werkstoffe im Bauwesen (IWB) to investigate the effect of various parameters on the sustained load performance of three adhesive anchor systems. T his appendix is reprinted with permission from Ronald Blochwitz. Overview The test series listed in ( Table B 1 ) were conducted at the University of Stuttgart; see Table 3 2 for a detailed test matrix. The short t erm (reference) and sustained load (creep) tests were performed in accordance with the test procedures described in AASHTO (2010c) TP 84 10 with the following modifications: Concrete The concrete mix design for all test series followed the requirements of DIN EN 2061. For this research project, the NCHRP panel chose to specify concrete with a compressive strength between 4000 and 6000 psi at time of testing to conform to typical DOT concrete mixes. This corresponds to a concrete C25/30 according to DIN E N 2061. Adhesive Only ICCES AC308 qualified adhesives were used. Adhesives of different chemistries from three manufacturers were chosen to investigate their sensitivity to sustained load. These were the same three adhesives used in the University of Florida tests.

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372 Anchor Due to a limitation of the test rigs for the creep tests, the anchor was limited to M12 metric threaded rods with approximately diam e ter (12mm). To avoid steel failure in short term reference tests, steel grade 12.9 was used, corre sponding to a 174 ksi ultimate strength and a 157 ksi yield strength. The embedment depth was hef = 3.15 (80mm). This depth was chosen in order to compare the results with the numerous creep tests that were previously performed at the IWB using the same embedment depth. Generally the anchors were centered at the bottom of the borehole with the use of a centering guide except for tests that were specifically performed to examine the behavior under special installation conditions (horizontal and overhead installation direction). The special centering guide used was not part of any of the tested anchoring systems. The 0.6 (15mm) high centering guide was placed in the bottom of a 3.75 (95mm) deep hole providing a 3.15 (80mm) embedment depth. The centering guide had a conical indention that guided the anchors during the installation procedure. Test P rocedure All tests were confined tests. The stress levels set for the sustained load (creep) test were initially at 85%, 75%, and 65% mean short term load for all test series and an additional stress level of 55% mean short term load for the baseline tests. After testing began, it was decided to adjust the stress levels due to early failure times at 85% and 75% mean short term load. Due to a limitation of the m easuring system, the frequency of data readings for the sustained load (creep) tests was not able to be varied and set to 10 minutes. Generally the first reading for a test occurred 120 seconds after the end of initial loading. Test A pparatus This section describes the test apparatus used for the short term (reference) and sustained load (creep) tests. Standard Short term (Reference) Test Apparatus The testing apparatus for the short term (reference) test used a 3.5 diameter x 0.04 thick Teflon PTFE (Po lytetrafluoroethylene) confining sheet with a 1 diameter

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373 hole in the middle placed under a circular 1.7 thick steel confining plate with a clearance hole of 0.8 ( Figure B 1 ). The confining sheet was used to correct for any surface irregularities in the concrete. The transducer mount was placed on top of the test specimen before the tripod for the hydraulic ram and the load cell was installed ( Figure B 2 ). The tripod consisted of an upper triangular steel plate connected to a lower circular steel plate by three M24 threaded rods at a distance of 14 ( Figure B 3 ). A LUKAS model LZOH 10/5020 22 kip hydraulic ram and a HBM model C6 45 kip load cell were attached on top of the tripod, using self centering ste el adapters. A M20 threaded loading rod was passed through the ram and load cell and was secured at the top with a washer and a nut ( Figure B 4 ). At the bottom, the loading rod was connected to the coupler which was connected to the anchor ( Figure B 5 ). The coupler provided a nonrigid connection between the anchor and the loadi ng rod by utilizing axial spherical plain bearings at all connections except the connection to the loading rod. The coupler also allowed for the positioning of the linear transducer directly on top of the anchor (direct measuring). Transducer mount. Figure B 6 shows the transducer mount on top of the test specimen with the linear transducer installed. The transducer was clamped into an aluminum cross beam that was mounted on a steel ring with two threaded rods. The threaded rods penetrated the ring and served as feet for the mount. With an additional threaded rod, the steel ring worked as a tripod. The mount (without cross beam and transducer) was placed directly on the concrete surface before the tripod of the hydraulic ram and the load cell was installed.

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374 Figure B 7 shows the transducer mount after the installation of the tr ipod. The crossbeam with the transducer was adjusted, fixed to the mount and locked with two size M10 nuts. Two coil springs were placed on the locknuts and connected to two levers attached to the tripod. The springs would push the mount downwards to t he concrete surface keeping it in position without transferring vibrations or horizontal loads from the test rig to the transducer during loading. Except for the springs, the transducer mount had no contact to the rest of the test rig. Standard Sustained L oad (Creep) Test Apparatus The testing apparatus for the sustained load (creep) tests used the same Teflon PTFE (Polytetrafluoroethylene) confining sheet. Instead of the steel confining plate that was used in the short term load test apparatus, a twopart confining plate was used for the sustained load tests to make the installation of the test specimens easier. The dimensions of the confinement sheet and plate were unchanged. The equipment for sustained load testing of bonded anchors at the IWB, Univer sity of Stuttgart, was developed by IWB personnel in 2008. Two different types of heating chambers were developed. Figure B 8 shows the large heating box with two backto back heating chambers. Each heating chamber contained three single test rigs. There were six large heating boxes installed at the IWB with a total number of 36 test rigs. Figure B 9 shows the small heating chamber that contained a single test rig. There were 26 small heating chambers installed at the IWB. To apply the sustained loads, large packages of disc springs were used ( Figure B 10). They provided low spring stiffness, which minimized the loss of load when the anchors displaced.

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375 The disc springs were manufactured by Schnorr GmbH, Sindelfingen. The item numbers of the types used are 021 400 (6 x 3 x 0.31, max. ~ 20 kips) and 021 350 (6 x 3 x 0.23, max. ~ 11 kips). The spring characteristics are shown in Figure B 11 A spring package usually consisted of at least 28 disc springs. Before the packages could be used for the tests, they were loaded for several days with the required test load to avoid any r elaxation effect of the springs during testing. The M12 diameter anchor was connected to the M20 diameter loading rod by means of the same non rigid coupler as in the s hort term load test apparatus. Linear pots were used to measure displacement in the sam e configuration as in the short term load test apparatus. A special loading system was developed to apply the loads to the spring packages ( Figure B 12 and Figure B 13). Two LUKAS model LFC 23/11 (50 kip) hydraulic rams were placed on top of a Burster model 8526 22 kip load cell. It was designed to avoid any effects to the applied loads from deformations of the test rig and to avoid any risk to the operator in case of failing during the loading process. No loss of load had to be taken into account due to unloading of the loading system. During loading, the load cell measured the transfer of force from the spring to the anchor. Once the desired load was achieved, the nut between coupler and anchor was tightened and the pressure in the rams was released. Specimen P reparation The test specimens consisted of three parts; the concrete test member, the adhesive, and the anchor rod.

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376 Concrete Test Member The concrete test members for the short term (reference) tests and the sustained load (creep) tests were poured in steel cylinders with an 8 inner diameter, 6 height, and a wall thickness of ( Figure B 14). No reinforcement was used. In addition, 30 x 30 x 6 concrete slabs were cast from the same batches for additional reference tests for test series 05, 06, and for extras. The pour dates and number of test blocks produced in each series are listed in Table B 2 The concrete for all mixes was batched, mixed, and placed by Friedrich Rau GmbH & Co. KG, Ebhausen, according to DIN EN 2061. Concrete with round river gravel without any admixtures was specified with a mean compressive strength between 4000 and 6000 psi during testing. All of the materials were batched by weight. After mixing the concrete was placed into the steel cylinders with shovels and vibrated on a vibration table. Due to size of the concrete mixer, the concrete for the research project was made in two batches. The concrete mix designs are included in Appendix A Following the pour, the concrete was cured according to DIN EN 2061 for 28 days. Concrete compressive strength was de termined by testing the cubes in general accordance with DIN EN 2061 on a Toni Technik model 1515 compression machine at the laboratory of the IWB, University of Stuttgart ( Figure B 15). The average compressive strength for each series is presented in Table B 3 and Table B 4 Adhesive The same three adhesives identified earlier were used. The three adhesive products were stored at the laboratory of the IWB. Because it was not possible to environmentally control the whole laboratory the adhesives had to be conditioned to the

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377 specified setting temperature prior to every installation. This conditioning was done in a Noske Kaeser model KSP 502/40 H climate chamber ( Figure B 17) at the laboratory. Anchor Rods Size M12 threaded rods and nuts were used as specified in ISO 1502. The steel grade was 12.9 which corresponds to 174 ksi ultimate strength and 157 ksi yield strength. The rods were galvanized to prevent rusting and to ensure nearly identical surface properties for all tests, even if the batch or the manufacturer changed during the project. They were delivered by Ferdinand Gross GmbH & Co. KG of LeinfeldenEchterdingen. The anchor rods were cut to a length of 6.7 from 39 stock and their ends ground. The bottom end of the anchor was ground to a 45 cone ( Figure B 16) in order to fit into a centering guide placed at the bottom of the drilled hole (except for test series 5 and 6). Prior to installation, the rods were cleaned with acetone and allowed to air dry. Instrumentati on Measurement Displacement. A direct measurement of the anchor displacement was measured with Novotechnik model TRS25 potentiometric linear transducers. Load. The tension in the anchor was measured indirectly as a compressive reaction of either the hydr aulic ram or the compression spring in the test apparatus. For the short term (reference) tests, the load was measured by a HBM model C6 45 kip load cell connected to the HBM model Spider 8 data acquisition system. The data logging was done with a PC using DIAdem 10. For the sustained load (creep) tests, the loads during the loading process were measured by a Burster model 8526 22 kip load cell. Once the load was applied to the anchor, the loading system including the load cell

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378 was removed. After removi ng the load cell, it was not possible to monitor the loads that were actually applied to the anchor without disturbing the tests. However, the stiffness of the spring packages was chosen to limit the loss of load to 2% f or an anchor movement of 0.04. Tem perature The temperature of the test specimens could not be measured directly during the tests. Due to the small specimen size, a hole could not be drilled without affecting the load distribution inside the specimens. To guarantee that the required tem peratures were reached before loading transfer, the required conditioning times were determined in advance using a thermocouple equipped anchor set into a standard test specimen. This temperature calibration specimen was connected to the HBM model Spider 8 data acquisition system and calibrated using a Testo model t110 digital thermometer, calibrated on October 08, 2009 and October 24, 2011. The data logging was performed with a PC running DIAdem 10. Ambient air temperature in each test chamber was measure d and controlled by GEFRAN model 400DR 1 temperature controllers. The temperature sensors attached to the controllers were Electrotherm type K2RS PT100 sensors. All heating systems, consisting of sensor, controller and heating elements were calibrated using the temperature calibration specimen. It was not possible to monitor the temperature of each chamber. The function of the temperature controllers were checked periodically with a calibrated Testo model t110 digital thermometer. Humidity. The relati ve humidity within the test chambers could not be measured and controlled. Time. Time was measured using the computers internal clock.

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379 Instrument Calibration Displacement in short term tests. The Novotechnik model TRS25 potentiometric linear transducer used in the short term reference tests was calibrated on May 26, 2010, using the Mitutoyo Gauge Block Set No. BM332 1/PD, calibrated on April 2008. Displacement in sustained load tests. The Novotechnik model TRS25 potentiometric linear transducer used in the sustained load test could not be calibrated as the creep displacements that occur in sustained load tests were below the accuracy guaranteed by the manufacturer. The accuracy was also affected by the increased temperature. Therefore all measured creep displacements could only be judged qualitatively. All transducers used for long term testing were checked for proper functioning before each test. The measurements were adjusted for variations in power supply voltage and normalized to a 9 volt power supply. Load. The Burster model 8526 22 kip load cell of the loading system for the sustained load tests was periodically calibrated against one of three HBM model C6 45 kip load cells t hat were used in the short term reference tests and for the loading of the disc spring packages in the sustained load tests. The HBM load cells were calibrated on October 28, 2009 & October 17, 2011 (ID no.: KMD006), December 11, 2009 & December 13, 2009 (ID no.: KMD009) and July 12, 2010 (ID no.: KMD010) at the MPA Stuttgart (Material Testing Institute University of Stuttgart) according to DKD standards (Deutscher Kalibrierdienst). The spring packages were not calibrated as all loads were applied using a calibrated load cell. For determining the loss of load due to anchor movement the spring constants provided by the manufacturer were used.

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380 Compressive s trength. The compressive strength of concrete cubes was tested on a Toni Technik model 1515 compression machine ( Figure B 15) calibrated on September 11, 2008 and September 13, 2010 at the MPA Stuttgart (Material Testing Institute University of Stuttgart) according to DKD standards (Deutscher Kalibrierdienst). Temperature. For the conditioning of the test specimens prior to the installation of the anchors and for conditioning at elevated test temperature in the short term test, the Noske Kaeser model KSP 502/40 H climate chamber ( Figure B 17) was used, calibrated on August 06, 2008 and August 18, 2010. For the periodical checking of the temperature of the heating chambers, the Testo model t110 digital thermometer was used, factory calibrated on October 08, 2009 and October 24, 2011 according to DKD standards (Deutscher Kalibrierdienst). T he temperature sensors in the test chambers were not calibrated separately but in combination with their controller and heating elements, using an original test specimen with a thermocouple equipped anchor installed. This temperature calibration specimen was calibrated against the Testo model t110 digital thermometer. Humidity. There were no humidity sensors installed. Environmental C ontrol Standard Temperature The adhesive was stored at the laboratory of the IWB without special air conditioning. The tem perature was 73F 9F. Prior to installation, the test specimens, the anchors and the adhesives were conditioned in the NoskeKaeser model KSP 502/40 H climate chamber ( Figure B 17). The chamber had a temperature range of 40F to 356F.

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381 Elevated Temperature The Noske Kaeser model KSP 502/40 H climate chamber was used for conditioning of the test specimens prior to every installation and for elevated testing temperatures in short term reference tests. Data M anagement and A cquisition Generally a Microsoft compatible computer was used for the data acquisition. For short term testing, National Instruments data acquisition software DIAdem10 was installed with s pecial drivers for the HBM mode Spider 8 data acquisition system. The measured values included load and displacement. For sustained load testing, the Measure Foundry 5 data acquisition software from Data Translation was used together with the Data Transl ation DT9803 USB connected measuring device. A special setup was developed at the IWB to automatically acquire and log the data. Measured values included the power supply voltage (9 volt), transducer voltage, and time. The voltage of the transducers re presented the relative position of the transducers, whereas 0V represented the minimum transducer position and 9V represented the maximum transducer position. No calculations were performed before logging. Generally the logging interval was 10 minutes. D ue to minor fluctuations in the nine volt power supply, the Data Translation program recorded the power supply voltage with each data reading and the readings of the transducer positions were appropriately adjusted to a normalized nine volt power supply.

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382 Data Acquisition Software for Short term (Reference) Tests For short term testing, DIAdem 10 was used, published by National Instruments ( Figure B 18). A load versus displacement curve was displayed on the screen for real time feedback. Load, displacement, and time readings were recorded at a frequency of 5 Hz and stored as Microsoft Excel file for analyzing. Data Acquisition Software for Sustained L oad (creep) Te sts For sustained load testing, Measure Foundry 5 was used, designed especially for the data acquisition devices from Data Translation. It used a graphical programming interface that gave access to every function of the measuring device and let the user build customized setups. Since most of the test chambers were not located in the IWB laboratory, the tests could not be observed daily. Therefore it was decided to build a very robust setup which only triggered the data acquisition of the measuring devi ce in a 10 minute interval and wrote the transferred data as a simple ASCII file to the hard disk ( Figure B 19). Further analysis was done in a second process using Microsoft Excel. Installation P rocedure The standard installation procedure is described below which was followed for test series 2, 3, 4, 5, 6, 8, 10 and 11. Standard Baseline Installation Procedure All anchors were installed according to the MPII. The holes were created with a 0.55 (14mm) carbide tipped concrete bit as specified by the manufacturer and a HiltiTM model TE36 hammer drill. A drilling jig ( Figure B 20) with a depth stop was used to ensure that the holes were drilled perpendicular to the surface of the concrete and to the correct depth. The holes were drilled 0.6 deeper than then embedment depth to allow for the placement of a centering guide at the bottom of the hole.

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383 The spoil at the concrete surface was removed with a vacuum prior to cleaning the hole. The holes were cleaned according to the MPII which generally included, blowing with oilfree compressed air, brushing with a steel brush provided by the manufacturer, and then blowing again with compressed air until no dust was discharged from the hole. Durations and numbers of brushing/blowing cycles varied by manufacturer, but for each case th e holes were cleaned according to the MPII. Details of the full cleaning procedure are listed in Table 4 4 To prevent dust from blowing into the operators mouth and eyes, an adaptor for the vacuum ( Figure B 21) was used to capture the dust ejected from the hole when blowing with compressed air. This adaptor attached to the vacuu m hose and allowed the compressed air nozzle to be easily inserted and removed. Prior to installation, a centering tool ( Figure B 22 and Figure B 23 ) was inserted into the hole and a concentric circle was drawn on the surface of the concrete to aid in centering the anchor. A plastic centering guide ( Figure B 24) was placed in the bottom of the hole. The adhesive products were dispensed with a manufacturer supplied cartridge gun. According to the MPII, several squeezes of adhesive were discharged and disposed of before dispensing into the holes to ensure that the adhesive was of uniform color and consistency indicating that it was properly/thoroughly mixed. The anchors were wiped clean with acetone and allowed to air dry. The anchor rod was rotated counterclockwise and jiggled while it was installed in the hole until the tip of the anchor seated into the centering guide at the bottom of the hole. Excess adhesive was wiped from the surface and the centering ring coated with wax to prevent

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384 adhering with the adhesive ( Figure B 25) was placed over the anchor and the anchor was centered and plumbed vertical. The anchors were left undisturbed during the specified gel/working time and the adhesive was allowed to cure for seven days prior to conditioning. Exceptions to the Standard Baseline Installation Procedure All tests of series 5 and 6 were conducted without using a centering guide. All of the tests of series 10 and 11 were installed at 32F. Specimen C onditioning Upon completion of the seven day adhesive curing period, the temperature conditioning started. Usually the conditioning took 18 hours. Immediately after conditioning the short term tests wer e conducted and the sustained load tests were loaded. Testing P rocedure The standard testing procedures for the short term (reference) and sustained load (creep) tests are described below which were followed for test series 2, 3, 4, 5, 6, 8, 10, 11 Standar d Short t erm (Reference) Test Procedure Immediately prior to testing, the test specimen was removed from the climate chamber and exposed to normal ambient temperature. To avoid nonadmissible loss of temperature the installation of the test apparatus des cribed below was finished within 120 seconds. A 0.04 thick PTFE confining sheet and 1.7 thick circular steel confining plate were placed over the anchor. The measuring mount for the linear transducer was placed on top of the concrete surface with the anchor centered in the middle of the base ring. The tripod, the LUKAS model LZOH 10/5020 22kip hydraulic ram, the HBM

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385 model C6 45 kip load cell and the loading rod were placed together on top of the confining plate. The coupler was attached to the anchor and connected to the loading rod. Finally the cross bar with the transducer installed was attached to the measuring mount and the coil springs were installed to keep the measuring mount in position. The hydraulic ram was connected to an electrically operated hydraulic pump installed inside a measuring cabinet. The transducer and the load cell were connected to a HBM Spider 8 data acquisition system installed inside the measuring cabinet, connected to a PC running DIAdem under Microsoft Windows Vista. The software was initialized with the appropriate sensor parameters (calibration factors, etc.) and checked for proper functioning. The anchors were loaded at a constant pump rate (i.e., displacement controlled). The pump rate was adjusted to get failure within 60 to 180 seconds as specified in the ETAG001. The DIAdem program automatically recorded the test data in a proprietary format. After finishing the tests, the data was exported to a M icrosoft Excel spreadsheet. Standard Sustained L oad (Creep) Te st Procedure The disc spring packages were compressed using the same LUKAS LZOH 10/50 20 22kip and HBM model C6 45kip load cells that were used in the short term tests and placed into the test rig between two triangular steel plates ( Figure B 26). Both steel plates were aligned by the same size M30 treaded rods that passed through holes in each corner of the plates surrounding the disc spring package. Both triangular steel plates could be locked with M30 nuts in any desired vertical position along the M30 treaded rods. To compress the spring packages, the upper steel plate was locked and the lower steel plate pushed upwards. When the desired load was

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386 reached, the lower steel plate was locked and the pressure in the hydraulic ram released. In the following paragraph, the set of triangular steel plates with the compressed disc spring package fixed in between is referred to as the spring frame. After the spring frame was adjusted, a third triangular steel plate was installed to the top of the test rig and fixed with M30 nuts in the same way. From above, the same measuring mount that was used in the short term tests was attached upsidedown to the third steel plate. The test specimen was placed upsidedown on top of the third steel plate in the same manner, with the PTFE confining sheet and the twopart steel confining plate placed in between. The coupler was installed to the anchor as described in the short term (reference) tests. The loading rod was passed through the spring package and the upper end was connected to the bottom of the coupler. A nut was attached to the lower end of the loading rod and hand tightened, bearing against the lower triangular steel plate of the spring frame. Finally the cross bar with the transducer installed was attached to the measuring mount and the coil springs were installed pushing the measuring mount against the concrete surface keeping it in position during testing. After installation, the temperature was raised to the test temperature. Once the conditioning period elapsed, the loading system was attached to the lower end of the loading rod bearing against the lower steel plate of the spring frame. The load was applied to the anchor with a hand operated hydraulic pump. Once the preload force of the spring package was reached, the M30 nuts that supported the lower steel plate of the spring frame were loosened and screwed downwards before the nut at the lower end of the loading rod was screwed upwards against the lower steel plate of

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387 the spring frame and hand tightened. Finally the pressure was released from the hydraulic rams and the loading system was detached. During the loading procedure, the load was permanently observed using the Burster model 8526 22 kip load cell (which is an integrated part of the loading system) and the HBM Spider 8 data acquisition system. Exceptions to the Standard Baseline Testing Procedure All of the tests of series 3 were conducted at 120F and those of series 4 were conducted at 70F. All of the tests of series 8 were conducted in moist concrete during service. The specimens were watered for 24 hrs. Immediately after the watering process, the test specimens were put into plastic bags to prevent them from drying. The anchors were guided through small holes in the plastic bags so that the loading equipment could be attached to the anchors as usual. After heating up the specimens and loading the anchors, the specimens could be checked anytime and rewetted if neces sary through the mouth of the bag. All of the tests for series 10 were conducted at 32F. Post Test Procedure After sustained load failure occurred the anchors could not be extracted from the test specimens by pulling them out without destroying the remai ning mortar shell that surrounds the anchor. Instead the anchors were extracted by splitting the test specimens as follows. The concrete cylinder was pressed out of the surrounding steel ring using a hydraulic ram. A 1 diameter hole was drilled into the concrete at a distance of 0.8 from the anchor. With a special wedge that is usually used to generate cracks in concrete slabs, the concrete cone was split in half. Usually the anchor could be extracted now with some gentle strokes of a hammer perpendi cular towards the

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388 head of the anchor. Once the anchor was separated from the concrete the actual failure could be determined.

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389 Table B 1 Test descriptions Test s eries Test d escription 2 Baseline 3 Service temperature: +120F 4 Service temperature: +70F 5 Installation direction: horizontal 6 Installation direction: overhead 8 Moisture during installation 10 Installation temperature: MFR min Service temperature: MFR min 11 Installation temperature: MFR min Service temperature : 110F Table B 2 Concrete pour details Concrete m ix Pour d ate Number of cylindrical t est m embers Number of sustained load t est m embers Notes A April 07, 2010 85 6 B September 17, 2010 100 3 Table B 3 Concrete series US A average compressive strength Concrete series Pour d ate Average c ompressive s trength (psi) 7 day 28 day 41 day 82 day 86 day 462 d ay a A April 07, 2010 3902 5279 5656 6280 5787 a Due to the unexpected long test period, the last group of four test samples of the first batch had to be used for compression testing when series S5 and S6 were started. The compressive strength at the end of the project has to be estimated (e.g. according to Weber, 1979) Table B 4 Concrete series US B average compressive strength Concrete s eries Pour d ate Average c ompressive s trength (psi) 7 day 28 day 538 day B Sept. 17, 2010 3031 4279 6193

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390 Figure B 1 Test specimen with PTFE sheet and confining plate installed (photo courtesy of Ronald Blochwitz) Figure B 2 Transducer mount on top of the test specimen (photo courtesy of Ronald Blochwitz)

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391 Figure B 3 Tripod on top of the test specimens (photo courtesy of Ronald Blochwitz)

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392 Figure B 4 Hydraulic ram and load cell on top of the tripod (photo courtesy of Ronald Blochwitz)

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393 Figure B 5 Coupler installed between loading rod and anchor (photo courtesy of Ronald Blochwitz) Figure B 6 Transducer mount (photo courtesy of Ronald Blochwitz)

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394 Figure B 7 Transducer mount and transducer installed (photo courtesy of Ronald Blochwitz) Figure B 8 Illustration of the large heating chamber (containing three test rigs)

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395 Figure B 9 Small heating chamber (containing a single test rig) (photo courtesy of Ronald Blochwitz) Figure B 10. Disc spring package (photo courtesy of Ronald Blochwitz)

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396 Figure B 11. Disc spring characteristics Figure B 12. Loading system (photo courtesy of Ronald Blochwitz)

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397 Figure B 13. Loading system installed (photo courtesy of Ronald Blochwitz) Figure B 14. Typical concrete test specimen (photo courtesy of Ronald Blochwitz)

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398 Figure B 15. Compression machine (photo courtesy of Ronald Blochwitz) Figure B 16. Anchor showing 45 cone to fit into centering guide (photo courtesy of author)

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399 Figure B 17. Climate chamber (photo courtesy of Ronald Blochwitz) Figure B 18. Screenshot of NI DIAdem 10.2 data acquisition program

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400 Figure B 19. Sustained load test setup, built with D ata T ranslation M easure Foundry 5 Figure B 20. Drilling rig and hammer drill (photo courtesy of author)

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401 Figure B 21. Vacuum adaptor (photo courtesy of author) Figure B 22. Centering tool (photo courtesy of author)

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402 Figure B 23. Centering tool inserted in hole (photo courtesy of author) Figure B 24. Centering guide with anchor (photo courtesy of a uthor)

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403 Figure B 25. Anchor with centering ring (photo courtesy of author)

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404 Figure B 26. Illustration of the test rig with a vertical cut Transducer Anchor Cross bar Coupler Disc spring package Loading rod Spring frame Test specimen

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405 APPENDIX C ADHESIVE ALONE TESTS UNIVERSITY OF FLORID A This appendix presents the test program conducted under NCHRP project 0437 by Changhua Liu at the University of Florida to investigate the isolated sustained load and short term creep behavior of the adhesive alone. This appendix is reprinted with permission from Changhua Liu. Overview The test series listed in Table C 1 were conducted at the University of Florida; see Table 3 3 f or a detailed test matrix. The short term (reference) tests generally followed the test procedure found in ASTM D638 with the following modifications: Tested at 110F with an attached oven c hamber Crosshead speeds were 0.1, 0.4, and 0.2 (2.5, 10, and 5 mm) / minute respectively for adhesive A, B, and C depending on the brittleness of the sample The sustained load (creep) tests generally followed the test procedure found in ASTM D2990 with the following modifications: The weight for tensile creep was not directly applied to the specimen but through a lever arm system The strain was continuously measured by strain gauges Samples were conditioned as described in the following section Stress levels were selected to be 35%, 45%, 55% and 75% of the adhesives maximum tensile stress obtained from short term tests. Test A pparatus This section describes the test apparatus used for the dogbone and DMTA and creep testing.

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406 Dogbone Short term ( R eference) Testing Apparatus The short term testing was done on an INSTRON 5582 load frame ( Figure C 1 ) with a load cell capacity of 2250 pounds. The temperature of the sample was controlled by an oven accessary ( Figure C 2 ). Dogbone Sustained L oad ( C reep) Testing Apparatus The sustained load creep tests were done on custom built test frames ( Figure C 3 ). The sample was suspended from the frame by an eye hook. The load was applied to the sample through a 24 long lever arm with a 10:1 ratio and was transferred to the dogbone sample through a hook on the lever arm as well. The self weight of the lever arm resulted in around 80 pounds of base load on the sample and additional weight could be added to the end of the lever arm. Each test frame had two grips used to clamp the dogbone sample shown in Figure C 4 A jig was used to ensure a consistent clamping position of the dogbone. In addition, 60 grit sandpaper was inserted between the grip and the dogbone to increase the friction and prevent slippage between the dogbone and the grips. Once the dogbone sample was clamped by hand tightening the screws on the grips, the sample was then inserted into the test frames between the two hooks mentioned above. P rior to loading, the upper eyehooks height was adjusted until the lever arm was horizontal. With the lever arm supported, the lower hook would become disengaged. Such a design ensured the dogbone sample would not be subjected to a load prior to testing During testing, as the dogbone elongated during creep, the lever arm would gradually displace downwards.

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407 DSR Machine The DMTA and creep tests were performed on a TA instruments AR EX2000 DSR machine with a rectangular torsional grips and an Environment al Test Chamber (ETC). The heating of the ETC was achieved through a peltier element and the ETC was air cooled by a Thermo Cube is 10300A 1 AR system. Figure C 5 shows the DSR machine with t he ETC open for sample loading. Specimen F abrication This section describes the fabrication of specimens used for the dogbone and DMTA and creep testing. Adhesive The same three adhesives identified earlier were used in this port ion of the project. The three adhesive products were stored in an environmentally controlled room maintained within the temperature and humidity range specified by the manufacturers prior to installation. Dogbone Sample The silicone molds ( Figure C 6 ) for the dogbone samples were made from Dow Corning Silastic E RTV Silicone Rubber with dogbone shaped steel blanks. The steel dogbones were machined according to the Ty pe I dogbone shape specified in ASTM D638. Once the silicone was cured, the steel dogbones were removed. The dogbone samples were cast into the premade silicone molds directly from the tube. Due to the viscosity difference between the three adhesive, th ere was a slight difference in preparing the exposed smooth surface. Adhesives A and B were allowed to overflow the mold and a razor blade was used to screed the excessive adhesive in one pass thereby leaving a smooth surface. Later it was decided that s uch a procedure

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408 resulted in too rough a surface for adhesive A and the procedure was modified as follows. Once overfilled, a piece of glass was pressed against the mold to squeeze the excessive adhesive out. Since adhesive A showed almost no adhesion to glass, the glass was detached easily after the sample cured. Adhesive C was too sticky for any overfillscreed processing. Fortunately it was found that adhesive C would slowly flow before gelation and the final procedure for making adhesive C was to car efully control the amount of the adhesive injected into the mold and let the adhesive flow under gravity and form the smooth surface. Specimens for DMTA and Creep Testing The specimens for DMTA and creep testing ( Figure C 7 ) on the DSR machine were rectangular thin sheets with a thickness ranging around 0.039 (1.00mm), width of approximately 0.35 (9mm) and a length of approximately 2 (50mm). The precise control of the thickness of the specimen was very important for the accuracy of the measurement and every effort was made to ensure the sample thickness variation was within 0.0008 (0.02mm) throughout the sample length. A thin sheet was first made by casting a quantity of adhesive into an aluminum plate and placing spacers of 0.039 (1.00mm) thickness (glass slides were used) around edges of the plates. Another aluminum plate was placed on top of adhesive and pressed to squeeze out the excess adhesive. When the adhesive sheet was cured, the specimens were cut into small rectangular strips by a precision diamond saw. Again due to the different adhesion behavior of samples, the processing of the thin sheets was slightly different. For adhesive A, it was found that it did not adhere to the aluminum plate and they were t herefore directly placed onto the aluminum plate. For adhesives B and C, the

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409 aluminum plate was coved by a thin cyclic olefin copolymer sheet prior to casting the adhesives. Instrumentation This section describes the instrumentation used for the dogbone and DMTA and creep testing. Measurement Strain. The creep of the dogbone sample was measured with strain gauges. All strain gauges were purchased from MicroMeasurement. The gauge designation was C2A XX 250LW 350 for adhesives A and C while adhesive B used EP 08250 BF 350. Both types of strain gauges had an initial resistance of 350 ohm and a gauge factor slightly larger than 2(2.09 for B and 2.12 for A and C). The strain gauges used for adhesive B could detect strain up to 20% while for adhesives A and C the strain gauges had a limit of 3%. The measurement of the strain gauge resistance was through a quarter bridge setting. The strain of the short term tests was measured by an INSTRON 2630115 extensometer attached to the sample surface along the loading direction. Load. The tension in the dogbones was measured indirectly from a relationship to the load applied to the end of the lever arm. For the short term (reference) tests, the loads were measured directly by a load cell. Temperature. Ambient air temperature in the test chamber was measured by a Cincinnati SubZero EZT 560i Environmental Chamber Controller installed in the Cincinnati SubZero Model WM STH 11522 H/AC Walk In Stability Chamber. Analog cards installed in the Cincinnati SubZero E ZT 560i Environmental Chamber controller

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410 provided an analog signal output allowing the ambient air temperature to be monitored by the data acquisition system. Humidity. Relative humidity in the test chamber was measured by a Cincinnati Sub Zero EZT 560i E nvironmental Chamber Controller installed in the Cincinnati SubZero Model WM STH 11522 H/AC Walk In Stability Chamber. Analog cards installed in the Cincinnati Sub Zero EZT 560i Environmental Chamber controller provided an analog signal output allowing the humidity to be monitored by the data acquisition system. Time. Time was measured using the computers internal clock. Instrument Calibration Strain. The extensometer was automatically calibrated with the built in function of the measurement software. Load. The INSTRON 5582 calibrated its load cell electronically by the built in software function before every set of tests. The load cell was allowed to warm up for 15 minutes before calibration. Each test frame lever arm was calibrated with an Omega Engineering, Inc. Model ICCA 10K 10 kip load cell in order to determine the load applied to a dogbone specimen due to the addition of load on the end of the lever arm. The load cell was calibrated on an INSTRON System 3384 150 kN universal testing machi ne. Temperature. The National Semiconductor LM35 Precision Centigrade Temperature Sensors factory calibration was validated in June 2010 against a high quality mercury thermometer over a temperature range of 100F to 120F. The temperature sensor in the test chamber was calibrated by the factory. Humidity. The humidity sensor in the test chamber was calibrated by the factory.

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411 DSR m achine. The system inertial and rotational friction mapping was done with the built in function of the DSR machine software daily before every set of experiments. The stiffness of the DSR machine geometry was provided by the manufacture. Environmental C ontrol This section describes the environmental control for the dogbone tests. The environment for the DMTA and creep tests w as controlled via the testing device. Standard Temperature An air conditioned space was used to store and condition the adhesive and the dogbone specimens at 75F 10F and 50% 10% relativ e humidity. Elevated Temperature A 12 by 12 by 8 tall Cincinnati Sub Zero Model # WM STH 11522 H/AC Walk In Stability Chamber ( Figure 4 11 ) was used to condition and test at the elevated testing temperature of 110F +10F/ 0F and below 40% relative humidity for the sustained load (creep) test. The chamber was purchased and installed in the fall of 2009. The chamber had a temperature range of 20C to 60C ( 4F to 140F) and a relative humidity range of 10% to 95%. The chamber was equipped with a CSZ EZT 560i Touch Screen Controller to monitor and control the temperature and humidity. The dogbone test specimens were placed in test frames located on shelves five feet high in order to provide space for anchor testing below ( Figure C 8 Figure C 9 ). Data M anagement and A cquisition During the testing and conditioning of the test slabs to the elevated temperature, a Microsoft compatible computer ran several National Instruments L ab VIEW 8.6 software programs developed to collect, record, and display the data. Measured values included load, displacement, tem perature, humidity, and time. Data acquisition was

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412 performed with a National Instruments NI cDAQ 9172 chassis with several National Instruments NI 9219 modules and a NI 9205 module to interface with the instrumentation. Data acquisition for the DSR creep tests was conducted directly by the DSR machine. Data Sampling Program A LabVIEW 8.6 program ( Figure C 10) was developed to centrally sample data for every test. This program provided a half second time averaged record sampled at 2000 Hz. Global variables for each of the sixteen sustained load test frames were updated every half second to the computer memory to be read when needed by the separate LabVIEW programs for each test frame. Each global variable included a timestamp, strain, and environmental chamber temperature and humidity. Long Term (Creep) Test Program A LabVIEW 8.6 program ( Figure C 11) developed for this project was used for the sustained load (creep) test. Strain, temperature, and humidity readings were recorded at one of the following two conditionings: If the difference between the last recorded strain and current reading was larger than 2E 6 Every ten minutes if no change in strain larger than 2E 6 occurred A strain versus time curve ( Figure C 12) for each dogbone speci men was displayed on the screen for real time feedback. The latest data readings were displayed on the screen and each data reading was automatically recorded in a Microsoft Excel spreadsheet.

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413 Specimen P reparation P rocedure The standard specimen preparation procedure is described below for the dogbone specimens and the DMTA and creep specimens. Dogbone Specimen Preparation To prepare the dogbones for strain gauges, the center of the dogbone was first degreased using isopropyl alcohol, and then polished s uccessively using 120 and 300 grit sandpaper in the presence of the conditioning solvent provided from MicroMeasurement. After polishing, neutralizing solvent was applied to adjust the pH of the dogbone surface for optimal strain gauge adhesion. The strain gauge was attached to the degreased and polished dogbone along the principle strain direction using adhesive tape first for easy handling of the strain gauge. Extra care was taken during the handling of the strain gauges to ensure the strain gauges were never touched directly by fingers. After partly peeling away the adhesive tape along with the strain gauge, a thin layer of the M bond 10 adhesive from MicroMeasurement was applied underneath the strain gauge to permanently attach it to the dogbone sample. The M bond 10 adhesive was allowed to cure in the test chamber for two hours before the dogbone specimens were loaded. DMTA and Creep Specimen Preparation For samples A and B the thin sheets made for DMTA and creep testing were cut into the speci men strips after proper curing. For sample C, small white spots due to improper mixing were commonly present and care was taken to ensure that the final specimen strips were free of these imperfections.

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414 Specimen C onditioning This section discusses the specimen conditioning for the dogbone and DMTA and creep test specimens. Dogbone S hort term ( R eference) Testing The short term testing specimens were conditioned the same as the sustained load testing specimens as described below. Dogbone S ustained L oad ( C ree p) Testing Upon completion of the seven day adhesive curing period, the test specimens for test series 21 were placed into the 110F 35% humidity environmental test chamber for conditioning. The temperature of the environmental chamber as well as the humi dity in the environmental chamber were monitored and recorded. Testing began upon completion of the 24 hour conditioning period in the environmental test chamber. DMTA and Creep Testing The conditioning of the DMTA and creep testing samples was almost the same as the sustained load (creep) test. The only difference was that after 12 hours of conditioning inside the environmental test chamber the sheets were removed to be cut into small specimen strips. After cutting, the specimens were returned to the environmental test chamber for another 12 hours. Testing began after the second 12 hours of conditioning. Testing P rocedure The standard testing procedures for the short term (reference) tests, sustained load (creep) tests, and DMTA and creep tests are desc ribed below.

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415 Dogbone S hort t erm (Reference) Test Procedure Once the samples were conditioned, the area where the sample was clamped by the grip was roughed by sand paper and the samples were moved into the oven of the INSTRON for several minutes to reach 110F. The samples were clamped between the grip with sand paper for increased friction and a stable grip during test. An extensometer was then clipped onto the sample. Once the samples were loaded, they were allowed to equilibrate with the temperature for an additional five minutes. The extensometer was calibrated and both the extensometer and the load cell were zeroed. After entering the test speed and sample dimensions of the dogbone in the testing software, the test was started. Dogbone S ustained L oad (Creep) Test Procedure Once the dogbone specimens were conditioned and the strain gauges were attached, they were placed in the testing frame without additional weight placed on the lever arm and the lever arm was immediately supported so that no load was applied to the dogbone sample. The top eyehook was adjusted so that the initial position of the lever arm was horizontal as confirmed by a tubular spirit level. While still supported, additional steel weights as determined from the calibration factor s were applied to the lever arm. Subsequently, the strain gauge was connected to the data acquisition hardware. Finally, the testing began as one person removed the support underneath the lever arm while another person started the data acquisition proces s in LabVIEW. DMTA and Creep Test Procedure After the torsional grip was mounted in the DSR machine, calibration tests for the system inertial and rotational friction mapping were performed. The grips were then brought to within 0.1 (3mm) of each other a nd the software was allowed to determine

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416 the zero position of the grip gap, which corresponded to the length of the sample during testing. The dimension of the conditioned test strip was first measured and inputted into the DSR machine software and then placed into the grip and tightened to 5.3 inpounds (60 cm N) using a torque screwdriver. A 0.03 (0.75mm) spacer was used to align the specimen per recommendations of the DSR machine manufacturer. Next, the ETC was closed and the temperature inside set t o the desired experimental temperature through the DSR machine software. Once the temperature stabilized, the specimen would be conditioned at the temperature for ten minutes before testing. Due to the thin thickness of the specimen strip, ten minutes of conditioning was considered sufficient. Throughout the test, a 0.070.4 pound (0.30.2 N) tension force was applied to the specimen to compensate for any thermal expansion. Each creep test was thirty minutes in duration. The test specimen dimensions wer e entered into the DSR software and the shear stress was precisely controlled by the DSR software. The DSR machine recorded the radial displacement of one end of the strip in relation to the other end and automatically calculated the conversion of strain and compliance.

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417 Table C 1 Test descriptions Test s eries Test d escription 21 Baseline 22 Manufacturer c ure t ime

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418 Figure C 1 INSTRON tensile testing machine (photo courtesy of Laura Diers) Figure C 2 The oven, which pulls forward around the I NSTRON, used to keep the samples at temperature (photo courtesy of Laura Diers)

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419 Figure C 3 Test frames for sustained load dogbone testing (photo courtesy of Changhua Liu) Figure C 4 Dogbone specimen loaded in grips (photo courtesy of Changhua Liu)

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420 Figure C 5 DSR machine (photo courtesy of Alex Piper) Figure C 6 Silicon molds for casting dogbone specimens (photo courtesy of Changhua Liu)

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421 Figure C 7 DMTA and DSR creep specimens (photo courtesy of Changhua Liu) Figure C 8 Left side of testing chamber (photo courtesy of Changhua Liu)

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422 Figure C 9 Right side of testing chamber (photo courtesy of Changhua Liu) Figure C 10. Data sampling LabVIEW program

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423 Figure C 11. Sustained load test LabVIEW program (main screen) Figure C 12. Sustained load test LabVIEW program (strain plot)

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424 APPENDIX D SHORT TERM TEST RESULTS The following tables and figures present the short term test results conducted at the University of Florida and the University of Stuttgart. In the tables the tests are listed by their series and adhesive. In the figures, short term tests are identified as TS A ST R, where: TS: Test Series (0116, 21, 22) A: Signifies the adhesive type (A, B, or C) ST: Signifies short term test R: Test repetition number (1 13) The modified Thompson tau technique was used to test for out liers. In this method, the absolute value of the deviation ( i) of a data point from the mean is compared against the standard deviation ( sx) times Thompsons tau value ( ) which is tabulated by number of data points and can be found in most statistics textbooks. The modified Thompsons tau value is 1.572 for five data points and 1.798 for ten data points (Wheeler and Ganji (2004)). A data point is rejected if i > sx If a data point is rejected, the mean and standard deviation are recalculated from t he remaining values. Two data points listed in Table D 12 were determined to be outliers by the Thompson tau technique and chosen for rejection. These are assumed to have failed at lower bonds stresses due to incomplete curing issues with adhesive C as discussed earlier

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425 Table D 1 University of Florida short term anchor pullout test results failure loads Test Test r epetition (kips) 1 2 3 4 5 6 7 8 9 10 01A 21.3 20.3 20.2 19.4 20.4 18.8 18.2 21.3 18.5 19.5 01B 26.7 26.0 26.7 26.1 26.5 26.0 25.4 25.9 25.0 22.2 01C 26.3 28.6 22.4 26.6 26.9 27.5 26.8 25.1 27.4 25.8 07A 15.9 17.5 16.4 14.9 16.5 07B 22.2 25.8 24.8 23.7 23.8 07C 25.4 23.3 24.1 8.5 24.0 09A 17.0 18.8 18.9 18.5 19.0 09B 24.4 21.4 24.4 23.9 25.0 09C 22.9 19.3 22.0 21.6 20.9 12A 15.3 20.6 13.9 17.5 15.8 12B 21.7 22.1 24.8 19.7 24.1 12C 24.1 26.6 25.6 24.5 24.7 13A 11.0 11.5 12.1 10.6 14.4 13B 20.6 20.0 18.8 16.2 18.1 13C 23.0 23.1 23.1 23.3 23.4 14A 16.6 18.3 19.7 19.5 18.4 14B 26.2 22.5 20.8 21.0 26.8 14C 25.6 26.8 26.5 27.3 26.5 15A 17.8 16.8 18.2 17.8 16.5 15B 24.9 25.4 26.3 25.4 25.5 15C 25.3 25.2 25.6 23.8 24.1 16A 10.2 10.2 10.7 10.8 10.1 16B 11.2 9.4 12.0 11.7 10.7 16C 10.8 9.6 10.3 8.7 5.9

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426 Table D 2 University of Florida short term anchor pullout test results failure stresses Test Test r epetition (ksi) 1 2 3 4 5 6 7 8 9 10 01A 3.47 3.31 3.30 3.17 3.33 3.07 2.96 3.47 3.01 3.18 01B 4.36 4.24 4.36 4.25 4.31 4.24 4.14 4.23 4.07 3.62 01C 4.28 4.67 3.65 4.34 4.38 4.49 4.36 4.10 4.47 4.20 07A 2.60 2.85 2.67 2.43 2.69 07B 3.61 4.21 4.04 3.87 3.88 07C 4.15 3.80 3.93 1.39 3.91 09A 2.77 3.06 3.07 3.01 3.09 09B 3.97 3.49 3.98 3.90 4.07 09C 3.73 3.14 3.59 3.51 3.40 12A 2.49 3.35 2.27 2.85 2.58 12B 3.53 3.60 4.03 3.21 3.92 12C 3.93 4.33 4.18 3.99 4.03 13A 1.80 1.88 1.97 1.73 2.34 13B 3.36 3.26 3.07 2.65 2.95 13C 3.75 3.77 3.76 3.80 3.81 14A 2.71 2.98 3.21 3.18 2.99 14B 4.27 3.66 3.39 3.42 4.36 14C 4.16 4.37 4.33 4.45 4.32 15A 2.90 2.74 2.97 2.90 2.68 15B 4.05 4.15 4.29 4.14 4.16 15C 4.12 4.11 4.18 3.88 3.92 16A 1.67 1.66 1.74 1.77 1.64 16B 1.83 1.53 1.95 1.91 1.74 16C 1.76 1.56 1.67 1.41 0.96

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427 Table D 3 University of Florida short term anchor pullout test results failure displacements Test Test r epetition (in) 1 2 3 4 5 6 7 8 9 10 01A 0.047 0.048 0.044 0.044 0.048 0.040 0.043 0.044 0.037 0.038 01B 0.057 0.047 0.045 0.050 0.051 0.051 0.050 0.047 0.053 0.057 01C 0.052 0.047 0.051 0.043 0.051 0.041 0.040 0.051 0.047 0.039 07A 0.037 0.038 0.040 0.037 0.040 07B 0.050 0.055 0.060 0.049 0.058 07C 0.051 0.047 0.041 0.067 0.050 09A 0.038 0.044 0.041 0.042 0.037 09B 0.057 0.042 0.046 0.055 0.046 09C 0.043 0.035 0.040 0.041 0.044 12A 0.037 0.040 0.047 0.038 0.037 12B 0.036 0.047 0.045 0.043 0.036 12C 0.034 0.031 0.035 0.035 0.032 13A 0.024 0.024 0.023 0.021 0.034 13B 0.030 0.028 0.029 0.033 0.030 13C 0.030 0.032 0.033 0.030 0.032 14A 0.041 0.044 0.043 0.041 0.040 14B 0.047 0.044 0.045 0.043 0.051 14C 0.056 0.041 0.039 0.041 0.043 15A 0.036 0.033 0.043 0.034 0.035 15B 0.051 0.047 0.047 0.048 0.052 15C 0.048 0.037 0.041 0.040 0.036 16A 0.031 0.036 0.031 0.033 0.024 16B 0.026 0.015 0.035 0.029 0.023 16C 0.025 0.026 0.027 0.029 0.051

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428 Table D 4 University of Stuttgart shortterm anchor pullout test results failure loads Test Test r epetition (kips) 1 2 3 4 5 02A 14.6 15.5 14.6 13.9 15.1 02B 18.2 20.1 19.6 18.9 19.6 02C 18.2 18.2 18.3 17.6 20.1 03A Not selected for testing 03B 23.6 23.2 23.2 22.8 22.5 03C Not selected for testing 04A Not selected for testing 04B 26.5 27.7 27.8 26.7 27.2 04C Not selected for testing 05A 15.2 16.4 16.1 16.0 15.5 05B Not selected for testing 05C Not selected for testing 06A 16.0 17.0 16.1 15.9 15.4 06B Not selected for testing 06C Not selected for testing 08A Not selected for testing 08B 23.6 23.9 24.8 24.7 25.2 08C Not selected for testing 10A 19.3 19.3 17.8 19.7 18.5 10B Not selected for testing 10C Not selected for testing 11A 14.5 14.4 14.6 14.6 15.9 11B Not selected for testing 11C Not selected for testing

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429 Table D 5 University of Stuttgart shortterm anchor pullout test results failure stresses Test Test r epetition (ksi) 1 2 3 4 5 02A 3.13 3.32 3.13 2.97 3.23 02B 3.90 4.30 4.19 4.04 4.20 02C 3.89 3.89 3.91 3.76 4.30 03A Not selected for testing 03B 5.06 4.96 4.97 4.88 4.81 03C Not selected for testing 04A Not selected for testing 04B 5.67 5.93 5.95 5.72 5.82 04C Not selected for testing 05A 3.26 3.50 3.45 3.41 3.32 05B Not selected for testing 05C Not selected for testing 06A 3.41 3.63 3.45 3.39 3.29 06B Not selected for testing 06C Not selected for testing 08A Not selected for testing 08B 5.06 5.11 5.31 5.29 5.38 08C Not selected for testing 10A 4.12 4.13 3.81 4.22 3.96 10B Not selected for testing 10C Not selected for testing 11A 3.11 3.08 3.11 3.12 3.39 11B Not selected for testing 11C Not selected for testing

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430 Table D 6 University of Stuttgart short term anchor pullout test results failure displacements Test Test r epetition (in) 1 2 3 4 5 02A 0.023 0.023 0.023 0.021 0.028 02B 0.027 0.032 0.026 0.039 0.032 02C 0.029 0.039 0.030 0.034 0.032 03A Not selected for testing 03B 0.042 0.035 0.037 0.031 0.029 03C Not selected for testing 04A Not selected for testing 04B 0.044 0.064 0.067 0.046 0.052 04C Not selected for testing 05A 0.022 0.025 0.024 0.023 0.021 05B Not selected for testing 05C Not selected for testing 06A 0.025 0.022 0.023 0.024 0.021 06B Not selected for testing 06C Not selected for testing 08A Not selected for testing 08B 0.029 0.032 0.035 0.033 0.036 08C Not selected for testing 10A 0.015 0.016 0.015 0.017 0.015 10B Not selected for testing 10C Not selected for testing 11A 0.015 0.014 0.015 0.016 0.015 11B Not selected for testing 11C Not selected for testing Table D 7 University of Florida and University of Stuttgart late baseline short term test results failure loads Test Test r epetition (kips) 1 2 3 UF 01 A ST 18.0 18.6 UF 01 B ST 24.1 20.7 27.5 US 02 A ST 17.7 16.6 US 02 B ST 22.9 22.5 23.3 Table D 8 University of Florida and University of Stuttgart late baseline short term test results failure stresses Test Test r epetition (ksi) 1 2 3 UF 01 A ST 2.94 3.04 UF 01 B ST 3.92 3.38 4.49 US 02 A ST 3.79 3.55 US 02 B ST 4.89 4.80 4.99

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431 Table D 9 University of Florida and University of Stuttgart late baseline short term test results failure displacements Test Test r epetition (in) 1 2 3 UF 01 A ST 0.035 0.036 UF 01 B ST 0.043 0.047 0.051 US 02 A ST 0.020 0.018 US 02 B ST 0.026 0.032 0.039 Table D 10. University of Florida short term dogbone test results failure stresses Test Test r epetition (ksi) 1 2 3 4 5 21A 1.33 1.56 1.39 1.56 1.42 21B 7.09 6.79 7.30 5.89 7.00 21C 4.10 4.01 4.51 4.23 3.01 22A 1.52 1.55 1.66 1.47 1.41 22B 1.14 2.67 4.39 4.81 5.38 22C Unable to test due to brittleness Table D 11. University of Florida short term dogbone test results failure strains Test Test r epetition (in/in) 1 2 3 4 5 21A 0.003 0.004 0.005 0.005 0.003 21B 0.015 0.011 0.011 0.008 0.012 21C 0.005 0.005 0.006 0.006 0.004 22A 0.004 0.005 0.004 0.003 0.002 22B 0.013 0.021 0.017 0.012 0.012 22C Unable to test due to brittleness Table D 12. Results of modified Thompson tau technique Test series Adhesive Repetition value (kips) mean (kips) i (kips) s x (kips) Result 7 Moisture (installation) C 4 8.5 21.1 12.5 11.1 REJECT 16 Test set up (unconfined) C 5 5.9 9.0 3.2 3.0 REJECT

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432 Figure D 1 TS01A UF baseline a dhesive A short term load vs. displacement Figure D 2 TS01A UF baseline a dhesive A short term stress vs. displacement

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433 Figure D 3 TS01A UF baseline adhesive A late short term load vs. displacement Figure D 4 TS01A UF baseline adhesive A late short term stress vs. displacement

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434 Figure D 5 TS01 B UF baseline a dhesive B short term load vs. displacement Figure D 6 TS01 B UF baseline a dhesive B short term stress vs. displacement

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435 Figure D 7 TS01B UF baseline adhesive B late short term load vs. displacement Figure D 8 TS01B UF baseline adhesive B late short term stress vs. displacement

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436 Figure D 9 TS01 C UF baseline a dhesive C short term load vs. displacement Figure D 10. TS01 C UF baseline a dhesive C short term stress vs. displacement

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437 Figure D 11. TS0 2 A US baseline a dhesive A short term load vs. displacement Figure D 12. TS02A US baseline adhesive A short term stress vs. displacement

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438 Figure D 13. TS02A U S baseline adhesive A late short term load vs. displacement Figure D 14. TS02A US baseline adhesive A late short term stress vs. displacement

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439 Figure D 15. TS02B US baseline adhesive B short term load vs. displacement Figure D 16. TS02B US baseline adhesive B short term stress vs. displacement

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440 Figure D 17. TS02B US baseline adhesive B late short term load vs. displacement Figure D 18. TS02B US baseline adhesive B late short term stress vs. displacement

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441 Figure D 19. TS02C US baseline adhesive C short term load vs. displacement Figure D 20. TS02C US baseline adhesive C short term stress vs. displacement

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442 Figure D 21. TS03B 120F service temperature short term load vs. displacement Figure D 22. TS03B 120F service temperature short term stress vs. displacement

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443 Figure D 23. TS04B 70F service temperature short term load vs. displacement Figure D 24. TS04B 70F service temperature short term stress vs. displacement

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444 Figure D 25. TS05A horizontal installation short term load vs. displacement Figure D 26. TS05A horizontal installation short term stress vs. displacement

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445 Figure D 27. TS06A overhead installation short term load vs. displacement Figure D 28. TS06A overhead installation short term stress vs. displacement

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446 Figure D 29. TS07A moisture at installation short term load vs. displacement Figure D 30. TS07A moisture at installation short term stress vs. displacement

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447 Figure D 31. TS07B moisture at installation short term load vs. displacement Figure D 32. TS07B moisture at installation short term stress vs. displacement

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448 Figure D 33. TS07C moisture at installation short term load vs. displacement Figure D 34. TS07C moisture at installation short term stress vs. displacement

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449 Figure D 35. TS08B moisture during installation short term load vs. displacement Figure D 36. TS08B moisture during installation short term stress vs. displacement

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450 Figure D 37. TS09A partially cleaned hole short term load vs. displacement Figure D 38. TS09A partially cleaned hole short term stress vs. displacement

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451 Figure D 39. TS09B partially cleaned hole short term load vs. displacement Figure D 40. TS09B partially cleaned hole short term stress vs. displacement

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452 Figure D 41. TS09C partially cleaned hole short term load vs. displacement Figure D 42. TS09C partially cleaned hole short term stress vs. displacement

PAGE 453

453 Figure D 43. TS 10A MFR minimum installation temperature/MFR minimum service temperature short term load vs. displacement Figure D 44. TS10A MFR minimum installation temperature/MFR minimum service temperature short term stress vs. displacement

PAGE 454

454 Figure D 45. TS11A MFR minimum installation temperature/110 F service temperature short term load vs. displacement Figure D 46. TS11A MFR minimum installation temperature/110 F service temperature short term stress vs. displacement

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455 Figure D 47. TS12A DOT co ncrete mix short term load vs. displacement Figure D 48. TS12A DOT concrete mix short term stress vs. displacement

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456 Figure D 49. TS12B DOT concrete mix short term load vs. displacement Figure D 50. TS12B DOT concrete mix short term stress vs. displacement

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457 Figure D 51. TS12C DOT concrete mix short term load vs. displacement Figure D 52. TS12C DOT concrete mix short term stress vs. displacement

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458 Figure D 53. TS13A core drilled hole short term load vs. displacement Figure D 54. TS13A core drilled hole short term stress vs. displacement

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459 Figure D 55. TS13B core drilled hole short term load vs. displacement Figure D 56. TS13B core drilled hole short term stress vs. displacement

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460 Figure D 57. TS13C core drilled hole short term load vs. displacement Figure D 58. TS13C core drilled hole short term stress vs. displacement

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461 Figure D 59. TS14A fly ash mix short term load vs. displacement Figure D 60. TS14A fly ash mix short term stress vs. displacement

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462 Figure D 61. TS14B fly ash mix short term load vs. displacement Figure D 62. TS14B fly ash mix short term stress vs. displacement

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463 Figure D 63. TS14C fly ash mix short term load vs. displacement Figure D 64. TS14C fly ash mix short term stress vs. displacement

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464 Figure D 65. TS15A blast furnace slag mix short term load vs. displacement Figure D 66. TS15A blast furnace slag mix short term stress vs. displacement

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465 Figure D 67. TS15B blast furnace slag mix short term load vs. displacement Figure D 68. TS15B blast furnace slag mix short term stress vs. displacement

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466 Figure D 69. TS15C blast furnace slag mix short term load vs. displacement Figure D 70. TS15C blast furnace slag mix short term stress vs. displacement

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467 Figure D 71. TS16A unconfined setup mix short term load vs. displacement Figure D 72. TS16A unconfined setup mix short term stress vs. displacement

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468 Figure D 73. TS16B unconfined setup mix short term load vs. displacement Figure D 74. TS16B unconfined setup mix short term stress vs. displacement

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469 Figure D 75. TS16C unconfined setup mix short term load vs. displacement Figure D 76. TS16C unconfined setup mix short term stress vs. displa cement

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470 Figure D 77. TS21A adhesive alone dogbone baseline adhesive A short term stress vs. strain Figure D 78. TS21B adhesive alone dogbone baseline adhesive B short term stress vs. strain

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471 Figure D 79. TS21C adhesive alone dogbone baseline adhesive C short term stress vs. strain Figure D 80. TS22A manufacturer cure time short term stress vs. strain

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472 Figure D 81. TS22B manufacturer cure time short term stress vs. strain

PAGE 473

473 APPENDIX E ADHESIVE ANCHOR POST TEST SPLIT CORE INVESTIGATION Following anchor failure several of the anchors were cored from their concrete specimen using a Cincinnati Bickford core machine and a 2.5 core bit. The cores were then saw cut along their length on opposing sides to t he depth of the steel anchor. The sawn cores were then split open with a wide chisel and hammer. The report below lists the specimen name, test description, and whether it failed or was terminated. The load, time, and displacement values are the recordi ngs at failure or when the test was terminated. All photos are courtesy of Kunal Malpani. Split Core Photo Discussion 01 A 76 4 Baseline A Failure Load = 76% mean short term load Time = 0.17 hours Displacement = 0.074 in Failure mode: Concreteadhesive bond failure Anchor detached from both sides of split core

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474 Split Core Photo Discussion 01 A 68 5 Baseline A Failure Load = 68% mean short term load Time = 0.14 hours Displacement = 0.059 in Failure mode: Concreteadhesive bond failure Anchor attached to one sid e of split core 01 A 57 6 Baseline A Failure Load = 57% mean short term load Time = 36 hours Displacement = 0.070 in Failure mode: Adhesive shearing failure at threads Anchor attached to one side of split core 01 A 57 8 Baseline A Failure Load = 57% mean short term load Time = 55 hours Displacement = 0.050 in Failure mode: Creep of epoxy Anchor attached to one side of split core

PAGE 475

475 Split Core Photo Discussion 01 B 68 8 Baseline B Failed during loading Load = 68% mean short term load Time = 0.02 hours Displacement = 0.073 in Failure mode: Adhesive/anchor plug slipped in hole and stopped due to friction and reduction of load Adhesive reattached and concrete fractured at splitting Anchor attached to one side of split core 01 B 55 11 Baseline B Terminated Load = 55% mean short term load Time = 13,198 hours Displacement = 0.106 in Description: Fracture of concrete when splitting core 01 B 45 14 Baseline B Terminated Load = 45% mean short term load Time = 10,751 hours Displacement = 0.071 in Description: Fracture of concrete when splitting core

PAGE 476

476 Split Core Photo Discussion 01 B 44 15 Baseline B Terminated Load = 44% mean short term load Time = 10,751 hours Displacement = 0.078 in Description: Fracture of concrete when splitting core 01 C 44 13 Baseline C Terminated Load = 44% mean short term load Time = 10,752 hours Displacement = 0.081 in Description: Creep of epoxy Separation of adhesive from steel when splitting core Anchor attached to one side of split core 01 C 44 14 Baseline C Terminated Load = 44% mean short term load Time = 10,752 hours Displacement = 0.085 in Description: Creep of epoxy Separation of adhesive from steel when splitting core Anchor attached to one side of split core

PAGE 477

477 Split Core Photo Discussion 12 A 70 3 DOT Mix Failure Load = 70% mean short term load Time = 26 hours Displacement = 0.045 in Failure mode: Adhesive shearing failure at threads Anchor attached to one side of split core 12 A 64 5 DOT Mix Failure Load = 64% mean short term load Time = 2.8 hours Displacement = 0.173 in Failure mode: Mixed Concreteadhesive failure Mixed Adhesive shearing failure at threads Anchor attached to one side of split core 12 A 61 6 DOT Mix Failed during loading Load = 61% mean short term load Time = 0.10 hours Displacement = 0.249 in Failure mode: Concreteadhesive failure (predominate) Adhesive shearing failure at threads in lower 0.6in of anchor Anchor attached to one side of split core

PAGE 478

478 Split Core Photo Discussion 12 A 60 7 DOT Mix Failure Load = 60% mean short term load Time = 0.23 hours Displacement = 0.040 in Failure mode: Concreteadhesive failure Anchor attached to one side of split core 12 A 57 9 DOT Mix Failure Load = 57% mean short term load Time = 193 hours Displacement = 0.080 in Failure mode: Adhesive/anchor plug slipped in hole and stopped due to friction and reduction of load Adhesive reattached and threads exposed at splitting Anchor detached from both sides of split core 13 B 72 1 Core drill Failure Load = 72% mean short term load Time = 0.08 hours Displacement = 0.139 in Failure mode: Adhesive/anchor plug slipped in hole and stopped due to friction and reduction of load Portions of adhesive fractured within bond line Adhesive reattached and threads exposed at splitting Anchor attached to one side of split core

PAGE 479

479 Split Core Photo Discussion 13 B 68 3 Core dr ill Failure Load = 68% mean short term load Time = 0.03 hours Displacement = 0.053 in Failure mode: Adhesive/anchor plug slipped in hole and stopped due to friction and reduction of load Portions of adhesive fractured within bond line Adhesive reattached and concrete and adhesive fractured at splitting Anchor attached to one side of split core 13 B 67 5 Core drill Failure Load = 67% mean short term load Time = 0.16 hours Displacement = 0.069 in Failure mode: Concreteadhesive failure Anchor attached to one side of split core 13 B 57 6 Core drill Failure Load = 57% mean short term load Time = 21 hours Displacement = 0.171 in Failure mode: Concreteadhesive failure Anchor attached to one side of split core

PAGE 480

480 Split Core Photo Discussion 14 B 70 1 Fly ash Failure Load = 70% mean short term load Time = 60 hours Displacement = 0.134 in Failure mode: Concreteadhesive failure Cracking within adhesive Anchor attached to one side of split core 14 B 66 3 Fly ash Failure Load = 66% mean short term load Time = 5 hours Displacement = 0.122 in Failure mode: Adhesive/anchor plug slipped in hole and stopped due to friction and reduction of load Adhesive reattached and concrete fractured at splitting Anchor attached to one side of split core 14 B 59 5 Fly ash Failure L oad = 59% mean short term load Time = 472 hours Displacement = 0.098 in Failure mode: Adhesive/anchor plug slipped in hole and stopped due to friction and reduction of load Adhesive reattached and threads exposed at splitting Anchor attached to one side of split core

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481 Split Core Photo Discussion 14 B 53 7 Fly ash Failure Load = 53% mean short term load Time = 833 hours Displacement = 0.227 in Failure mode: Adhesive/anchor plug slipped in hole and stopped due to friction and reduction of load Adhesive reattached and concrete fractured at splitting Anchor attached to one side of split core 15 A 69 1 Blast Furnace Slag Failure Load = 69% mean short term load Time = 562 hours Displacement = 0.053 in Failure mode: Adhesive shearing failure at threads Anchor attached to one si de of split core 15 A 67 3 Blast Furnace Slag Failure Load = 67% mean short term load Time = 157 hours Displacement = 0.076 in Failure mode: Adhesive shearing failure at threads Anchor detached from both sides of split core

PAGE 482

482 Split Core Photo Discussion 15 A 57 5 Blast Furnace Slag Failure Load = 57% mean short term load Time = 124 hours Displacement = 0.047 in Failure mode: Concreteadhesive failure Cracking within adhesive at bottom half of anchor Anchor detached from both sides of split core 15 A 56 6 Blast Furnace Slag Failure Load = 56% mean short term load Time = 1,446 hours Displacement = 0.059 in Failure mode: Adhesive shearing failure at threads Anchor attached to one side of split core 12 C ST 2 DOT mix Failure Load = 100% mean short term load Time = 0.03 hours Displacement = 0.031 in Failure mode: Concreteadhesive failure

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483 Split Core Photo Discussion 12 C ST 4 DOT mix Failure Load = 100% mean short term load Time = 0.03 hours Displacement = 0.035 in Failure mode: Concreteadhesive failure 12 C ST 5 DOT mix Failure Load = 100% mean short term load Time = 0.03 hours Displacement = 0.032 in Failure mode: Concreteadhesive failure

PAGE 484

484 APPENDIX F TIME TO RUPTURE VERS US TIME TO TERTIARY CREEP COMPARISON Table F 1 University of Florida adhesive A anchor pullout tertiary creep and rupture failure times Test Tertiary c reep Rupture % Difference (hour) (hour) 01 A 88 1 0.06 0.06 0% 01 A 88 2 0.11 0.12 5% 01 A 87 3 0.05 0.06 0% 01 A 76 4 0.16 0.17 3% 01 A 68 5 0.13 0.14 1% 01 A 57 6 35.2 36.2 3% 01 A 57 7 49.2 52.2 6% 01 A 57 8 52.4 55.4 5% 01 A 57 9 58.1 59.1 2% 01 A 46 10 16,173 16,174 0% 01 A 46 11 Test still running 01 A 46 12 Test still running 01 A 36 13 Test terminated early 01 A 36 14 Test terminated early 01 A 36 15 Test terminated early Table F 2 University of Florida adhesive B anchor pullout tertiary creep and rupture failure times Test Tertiary c reep Rupture % Difference (hour) (hour) 01 B 81 1 0.11 0.11 4% 01 B 81 2 0.02 0.02 3% 01 B 75 3 0.04 0.04 1% 01 B 73 4 0.64 0.67 5% 01 B 72 5 0.29 0.32 10% 01 B 70 6 2.79 3.29 15% 01 B 70 7 3.47 3.64 5% 01 B 68 8 0.02 0.02 2% 01 B 67 9 33.1 35.1 6% 01 B 56 10 22.0 24.0 8% 01 B 55 11 Test terminated early 01 B 53 12 859 862 0% 01 B 45 13 Test terminated early 01 B 45 14 Test terminated early 01 B 44 15 Test terminated early

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485 Table F 3 University of Florida adhesive C anchor pullout tertiary creep and rupture failure times Test Tertiary c reep Rupture % Difference (hour) (hour) 01 C 80 1 0.31 0.32 3% 01 C 79 2 0.15 0.15 2% 01 C 72 3 11.2 11.2 1% 01 C 72 4 7.4 7.8 4% 01 C 72 5 36.4 37.4 3% 01 C 71 6 0.05 0.06 1% 01 C 70 7 0.23 0.25 10% 01 C 68 8 0.27 0.29 6% 01 C 59 9 0.02 0.03 3% 01 C 52 10 1 341 1 347 0% 01 C 50 11 1 572 1 576 0% 01 C 47 12 0.01 0.02 4% 01 C 44 13 Test terminated early 01 C 44 14 Test terminated early 01 C 44 15 Test terminated early Table F 4 University of Stuttgart adhesive A anchor pullout tertiary creep and rupture failure times Test Tertiary c reep Rupture % Difference (hour) (hour) 02 A 65 1 0.17 0.33 50% 02 A 65 2 0.17 0.33 50% 02 A 65 3 26.3 26.5 1% 02 A 55 4 36.8 37.0 0% 02 A 55 5 56.2 56.3 0% 02 A 55 6 511 511 0% 02 A 45 7 Test still running 02 A 45 8 674 674 0% 02 A 45 9 Test still running 02 A 35 10 Test still running 02 A 35 11 Test still running 02 A 35 12 Test still running

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4 86 Table F 5 University of Stuttgart adhesive B anchor pullout tertiary creep and rupture failure times Test Tertiary c reep Rupture % Difference (hour) (hour) 02 B 85 1 6.67 6.83 2% 02 B 85 2 2.00 2.17 8% 02 B 85 3 0.17 0.33 50% 02 B 75 4 0 0.17 0% 02 B 75 5 56.5 56.8 1% 02 B 75 6 194 194 0% 02 B 65 7 Test terminated early 02 B 65 8 Test terminated early 02 B 65 9 2 096 2 096 0% 02 B 55 10 Test terminated early 02 B 55 11 Test terminated early 02 B 55 12 Test terminated early Table F 6 University of Stuttgart adhesive C anchor pullout tertiary creep and rupture failure times Test Tertiary c reep Rupture % Difference (hour) (hour) 02 C 85 1 no data 0.03 02 C 85 2 no data 0.02 02 C 85 3 no data 0.02 02 C 75 4 no data 0.08 02 C 75 5 no data 0.08 02 C 75 6 no data 7.00 02 C 65 7 Test terminated early 02 C 65 8 370 371 0% 02 C 65 9 4 346 4 346 0% 02 C 55 10 Test terminated early 02 C 55 11 581 581 0% 02 C 55 12 Test terminated early

PAGE 487

487 APPENDIX G SUSTAINED LOAD CREEP T EST RESULTS The following figures are the sustained load displacement versus time to failure results for the anchor pullout tests performed at the University of Florida and the University of Stuttgart. Figure G 1 TS01A UF b aseline a dhesive A creep d isplacement vs. t ime

PAGE 488

488 Figure G 2 TS01B UF b aseline a dhesive B creep d isplacement vs. t ime Figure G 3 TS01C UF b aseline a dhesive C creep d isplacement vs. t ime

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489 Figure G 4 TS02A US b aseline a dhesive A creep d isplacement vs. t ime Figure G 5 TS02B US b aseline a dhesive B creep d isplacement vs. t ime

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490 Figure G 6 TS02C US b aseline a dhesive C creep d isplacement vs. t ime Figure G 7 TS03B 120F s ervice t emperature creep d isplacement vs. t ime

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491 Figure G 8 TS04B 70F service t emperature creep d isplacement vs. t ime Figure G 9 TS05A h orizontal i nstallation c reep d isplacement vs. t ime

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492 Figure G 10. TS06A o verhead i nstallation c reep d isplacement vs. t ime Figure G 11. TS07A m oisture at i nstallation creep d isplacement vs. t ime

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493 Figure G 12. TS08B m oisture during service creep d isplacement vs. t ime Figure G 13. TS09C p artially cleaned hole creep d isplacement vs. t ime 08 B 75 3 failed during loading

PAGE 494

494 Figure G 14. TS10A MFR minimum installation temperature/ MFR minimum service temperature creep d isplacement vs. t ime Figure G 15. TS11A MFR minimum installation temperature/110F service temperature creep d isplacement vs. t ime Instrumentation malfunctioned on 10A 701, should still be able to determine time to failure

PAGE 495

495 Figure G 16. TS12A DOT concrete mix creep d isplacement vs. t ime Figure G 17. TS13B core drilled hole creep d isplacement vs. t ime

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496 Figure G 18. TS14B f ly ash creep d isplacement vs. t ime Figure G 19. TS15A b last furnace slag creep d isplacement vs. t ime

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497 Figure G 20. TS16C u nconfined setup creep d isplacement vs. t ime

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498 APPENDIX H STRESS VERSUS TIME T O FAILURE PLOTS Figure H 1 TS 01A Stress versus Time to Failure Report

PAGE 499

499 Figure H 2 TS 01B Stress versus Time to Failure Report

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500 Figure H 3 TS 01C Stress versus Timeto Failure Report

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501 Figure H 4 TS 02A Stress versus Time to Failure Report

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502 Figure H 5 TS 02B Stress versus Time to Failure Report

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503 Figure H 6 TS 02C Stress versus Timeto Failure Report

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504 Figure H 7 TS 03B Stress versus Time to Failure Report

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505 Figure H 8 TS 04B Stress versus Time to Failure Report

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506 Figure H 9 TS 05A Stress versus Time to Failure Report

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507 Figure H 10. TS 06A Stress versus Time to Failure Report

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508 Figure H 11. TS 07A Stress versus Time to Failure Report

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509 Figure H 12. TS 08B Stress versus Time to Failure Report

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510 Figure H 13. TS 09C Stress versus Time to Failure Report

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511 Figure H 14. TS 10A Stress versus Time to Failure Report

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512 Figure H 15. TS 11A Stress versus Time to Failure Report

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513 Figure H 16. TS 12A Stress versus Time to Failure Report

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514 Figure H 17. TS 13B Stress versus Time to Failure Report

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515 Figure H 18. TS 14B Stress versus Time to Failure Report

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516 Figure H 19. TS 15A Stress versus Time to Failure Report

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517 Figure H 20. TS 16A Stress versus Time to Failure Report

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518 Figure H 21. TS 21A Stress versus Time to Failure Report

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519 Figure H 22. TS 21B Stress versus Time to Failure Report

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520 Figure H 23. TS 21C Stress versus Time to Failure Repor t

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521 Figure H 24. TS 22A Stress versus Time to Failure Report

PAGE 522

522 APPENDIX I ADHESIVE ALONE TEST RESULTS This appendix presents the test program conducted by Changhua Liu at the University of Florida to investigate the isolated sustained load and short term creep behavior of the adhesive alone under NCHRP project 0437. This appendix is reprinted with permission from Changhua Liu. Short term Results The short term test res ults for the dogbone specimens are presented in Appendix E. For the baseline test series, both adhesive A and C exhibited brittle failures. Adhesive B was more ductile, failing at much higher strains and loads. For test series 22 using MPII cure time, a dhesive A showed a slight increase in strength. Adhesive B had strengths about half of what was seen in the week cured specimens with significant scatter in the results (CoV = 0.47) due to the fact that the testing temperature was so close to the glass tr ansition temperature. Adhesive C was unable to be tested due to its high brittleness and would break in the grips of the testing machine. The alpha reduction factors for the influence of cure time are presented in Table I 1 Adhesives A and B were initially both chosen for sustained load investigation for test series 22, but due to the large ductility in the adhesive B manufacturer cured samples the tests could not be conducted. DMTA Results The first set of experiments was a temperature ramp at a speed of 5 degrees per minute at 1 Hz on the DSR machine and the results of samples A, B, and C are shown in Figure I 1 Figure I 2 and Figure I 3 respe ctively. Adhesive A showed a very broad and slow decrease of its shear storage modulus ( G ), which is the typical behavior of a

PAGE 523

523 noncrosslinked vinyl ester with wide range of molecular weight distribution. Both adhesives B and C displayed a plateau in th eir storage modulus at a temperature above their Tg, which indicated a crosslinked system. A narrower half width of the tan delta peak in sample A suggested a more homogenous crosslink network. A thermogravimetric analysis was conducted on the samples in which the samples were heated under air from 68F to 1470F at a rate of 18F/min while recording the weight change. Adhesive polymers will start to decompose into gas at temperatures greater than their decomposition temperature (typically larger than 735 F ). The decomposition was considered complete as evidenced by the fact that there was no weight change in the 1290F to 1470F range. The inorganic filler loading was calculated as the ratio of the final weight to the initial weight. The inorganic filer loading for the three samples was 60.0% for adhesive A, 38.9% for adhesive B, and 46.4% for adhesive C. Sustained Load Strain v ersus Time Results Figure I 4 Figure I 5 and Figure I 6 present the baseline strain vs. time plots of adh esives A, B, and C obtained through the sustained load creep test on dogbone specimens. Because of the different stress levels, the strain plots are scattered. Sustained Load Compliance v ersus Time Results Normalizing the strains according to their stress the compliance vs. time plots for all three adhesives are shown in Figure I 7 Figure I 8 and Figure I 9 As the majority of the compliance curves of adhesive C overlap each other, this gives a good indication that time temperature superposition should work for adhesive C. For adhesive A and B, the compliance curves at different stress levels differ from each other indicating a nonlinear creep rate dependence on stress level.

PAGE 524

524 Figure I 10 presents the short term creep response (log log plot) of adhesive A obtained through DSR creep tests at different temperatures. Figure I 11 presents the shifted creep response master curve at 110F. Due to the nonlinear behavior observed during the long term creep test of sample A and B, the short term creep curves might also be accelerated by the applied stress or the resulted strain. If the shift factors were directly obtained through shift of the creep curve, the shift factor will be coupled with the applied stress during the short term creep experiment. Since the frequency sweep measurements were conducted at very low strain levels, where the nonlinear behaviors effect is negligible in the linear viscoelastic region, the shift factor for time temperature superposition was obtained by shifting the frequency sweeps at different temperatures. As a res ult, eight frequency sweeps from 0.1 Hz to 10 Hz were performed at the same temperature of the sustained load creep tests with a maximum oscillation strain at 0.05% and shifted with 110F as the reference temperature. Using the shift factor obtained this way, the short term creep tests of adhesive A shown in Figure I 10 were shifted accordingly. The resulting master curve is shown in Figure I 11. Figure I 12 presents the comparison of the long term creep compliance curve of adhesive A to the shifted compliance curves from the short term creep test. Please note that the compliance of the curves from the creep test is the shear compliance and when compared with tensile compliance obtained through the sustained load creep tests, the shear compliance was divided by 2 ( 1 + ) where is the Poissons ratio of the epoxy (taken as 0.4). From this comparison, it can be seen that the prediction from the DSR creep test captured the overall trend and shape of the adhesive creep. However,

PAGE 525

525 due to the dependence of compliance on the stress level, the prediction from the DSR creep test could not be used quantitatively for adhesive A. Using the same treatment as described above for adhesive A, the short term DSR creep tests of adhesive B shown in Figure I 13 were shifted accordingly. The resulting master curve is shown in Figure I 14. The comparison between the compliance obtained from the sustained load creep test and the compliance predicted from the DSR creep tests are shown in Figure I 15. As with adhesive A, the prediction from the DSR creep test could not be used to directly predict the creep behavior of the dogbone. An apparent trend Figure I 15 i s as the load was increased during the long term test, the compliance increased at higher speeds over time, which should be due to the accelerating of the creep mechanism due to stress. To investigate if there was any simple stress time superposition relat ion, five DSR creep tests on adhesive B with shear stress ranging from 72.5, 2180, 2900, 3630 to 5080 psi (0.5, 15, 20, 25, 35 MPa) were tested on the DSR machine. Any further increase of the test stress level resulted in the failure of the test specimen. The raw and shifted curves are shown in Figure I 16 and Figure I 17. Only when the horizontal distance between the overlapping regions of two curves was a constant can satisfactory superposition be possible. The poor matches of the shifted curve indicated t hat no simple time stress superposition relationship existed for adhesive B. In effect, the horizontal distance between any two curves was not a constant but a function of compliance.

PAGE 526

526 The horizontal distance was calculated between any two pair of the compliance curves in Figure I 17 resulting in a total of =10 pairs and this value was plotted against the log10 of the corresponding compliance regions and is shown i n Figure I 18. Note that if a simple stress time superposition relation existed, there would be a few horizontal lines at different heights, which depended on the str ess level difference. For each curve in Figure I 18, three numbers were labeled, indicating the stress levels of the pair of compliance curves (labeled beside each c urve) and the difference between the two stress levels (labeled on each curve). Note that here 72.5 psi (0.5 MPa) was treated as 1450 psi (10 MPa) during the calculation of the stress difference as the calculated stress difference agreed with the curves t hey overlapped. A possible reason for the equivalence of 72.5 psi (0.5 MPa) with 1450 psi (10 MPa) could be that the nonlinear behavior of adhesive B was very low under low load, allowing 72.5 psi (0.5 MPa) to be treated as 1450 psi (10 MPa) in this analy sis. An interesting observation is that the curves with the same stress level difference seem to lie on top of each other. In addition, curves with higher stress level differences had higher shift factors. Similar treatment was done to the sustained load creep compliance curves of adhesive B which is shown in Figure I 19. Here the sustained load compliance axis was plotted linearly and the logs of the shift factor became a linear function of the compliance after a certain compliance value. A linear fit was performed for all the plots using the data points where compliance equaled 345 ksi1 (5e 10 Pa1) and was plotted in green on Figure I 19. Depending on the stress level, it took about 210 hours for the compliance to reach this value. Clearly the curve fits are very good for all curves and all the green plots roughly converge at the

PAGE 527

527 origin of the coordinate system. The slope of each curve fit and the stress difference for each of the fits was plotted in Figure I 20. A fairly good linear fit was obtained with R2 value equal 0.909 and slope = 44.7. In addition, the intercept on the y axis of the linear fit was very close to origin. As a result, we postulate that the shift factor for adhesive B can be approximated as: log = (I 1) where a is the shift factor, is the difference in stress, D is the compliance at which the shift factor is calculated, and C is a materials dependent constant which can be calculated from the slope of the red line of Figure I 20. Since the shift factor can be regarded as the viscosity ratio of two tests, from Equation I 1 it can be seen that the viscosity is proportional to e which indicates an Eyring type of viscosity stress relationship (Lee et al. (2009)). If there is no D term in Equation I 1 a simple stress time superposition is sufficient to describe the stress dependence of the creep behavior. Since stress time superposition assumed an unchanged creep mechanism, it is believed the presence of a D term indicates that there is a dependence of the underlying creep mechanism on the current state of the polymer during the creep test. The reason is still currently unknown, but the apparent linear r elationship of the log10 of the shift factor with D makes this a very interesting problem for further investigation. Figure I 21 shows the DSR creep test for adhesive C and Figure I 22 shows the resulting master curve. The shift was conducted by the built in TTS processing function of the DSR instrument. Very good agreement between the overlapping regions of the shifted curves showed that the time temperature superposition was valid f or adhesive C.

PAGE 528

528 The DSR master creep curve was overlaid with the compliance curves of adhesive C and is shown in Figure I 23. The compliance of the sustained load curv e did show agreement with the prediction curve at the early stage of creep but the creep predicted from DSR creep test grew faster than the tensile creep, which may be due to additional cure of the long term sample during the thousand hour long creep tests To test this hypothesis, the DSR creep samples were allowed to cure at 122F for two days and the master curves were constructed again as shown in Figure I 24. The discrepancy in the master curves and the long term creep compliance happened 100 hours later than the previous result, which confirmed the effect of the additional curing. Discussion and Recommendations Time temperature superposition can be a powerful tool for accelerated polymer testing. However, for epoxy resins used in commercial adhesive products, due to the complexity of their formula, one should not assume time temperature superposition always works. For adhesive C used in this study, time temperat ure superposition appears to be a reasonable method for long term creep prediction from very short term DSR creep tests. As for adhesives A and B, it was observed that linear viscoelastic behavior was not valid and the creep behavior depended on the appli ed stress. Although time stress supposition method was reported to be valid for a few polymers, we found the effect of stress to be more complicated. For adhesive B, the dependence of the shift factor on the stress was quite different between the sustained load creep tests and the short term DSR creep test. Nevertheless, it was found that after the creep compliance passed a certain point, the relationship between the shift factor, compliance, and stress becomes simple and apparently followed Equation I 1 As a result, we

PAGE 529

529 recommend the following steps to predict the sustained load creep rate from a set of relative short term tests. First, construct a master compliance curve from a DSR creep test within the linear viscoelastic range for very low stress lev els following the steps as shown in Figure I 13 to Figure I 14. The length of each DSR creep test can be as short as 30 minutes. Second, perform DSR creep tests under different stresses to see if there is any stress dependence on the compliance. If such dependence does exist, attempt the stress time supposition first. If successf ul, measure the short term creep tests at the desired stress level to obtain the shift factor and shift the master curve from step 1 accordingly. If the stress temperature superposition does not work, it is still possible to predict the sustained load creep rate. In this case, the short term creep tests must be conducted long enough until Equation I 1 becomes valid, which can take about 2 to 10 hours based on testing adhesive B. With this data, determine the C term in Equation I 1 Combined with the mast er compliance curve from step 1, the sustained load creep rate at any stress level can be obtained. Note that this only predicts creep rate and not time to failure.

PAGE 530

530 Table I 1 Summary of alpha reduction factors Test s eries Adhesive A Adhesive B Adhesive C 22 Manufacturer c ure t ime 1.05 0.54 --Note: Short term test results for adhesive C were not able to be obtained for the manufacturer cure time due to the brittleness of the material and its tendency to break when loaded into the I NSTRON

PAGE 531

531 Figure I 1 DMTA test results for adhesive A Figure I 2 DMTA test results for adhesive B 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 100.0 110.0 120.0 temperature (C 1.000E7 1.000E8 1.000E9 1.000E10 G' (Pa) 1.000E7 1.000E8 1.000E9 1.000E10 G'' (Pa) 0 10.00 20.00 30.00 40.00 50.00 60.00 70.00 80.00delta (degrees) 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 100.0 temperature (C 1.000E5 1.000E6 1.000E7 1.000E8 1.000E9 1.000E10 G' (Pa) 1.000E5 1.000E6 1.000E7 1.000E8 1.000E9 1.000E10 G'' (Pa) 0 0.2000 0.4000 0.6000 0.8000 1.000 1.200 1.400tan(delta)

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532 Figure I 3 DMTA test results for adhesive C Figure I 4 Adhesive A baseline strain vs. time plot for dogbone specimens 20.0 40.0 60.0 80.0 100.0 120.0 140.0 temperature (C 1.000E5 1.000E6 1.000E7 1.000E8 1.000E9 1.000E10 G' (Pa) 1.000E5 1.000E6 1.000E7 1.000E8 1.000E9 1.000E10 G'' (Pa) 0 0.2500 0.5000 0.7500 1.000 1.250 1.500 1.750tan(delta)

PAGE 533

533 Figure I 5 Adhesive B baseline strain vs. time plot for dogbone specimens Figure I 6 Adhesive C baseline strain vs. time plot for dogbone specimens

PAGE 534

534 Figure I 7 Adhesive A baseline compliance vs. time plot for dogbone specimens Figure I 8 Adhesive B baseline compliance vs. time plot for dogbone specimens

PAGE 535

535 Figure I 9 Adhesive C baseline compliance vs. time plot for dogbone specimens Figure I 10. Compliance versus time plot for DSR creep test of adhesive A at different temperatures

PAGE 536

536 Figure I 11. Shifted master compliance curve for adhesive A using 43C as a reference temperature Figure I 12. Comparison between predicted compliance from the DSR creep test and the sustained load creep tests on dogbone samples for adhesive A

PAGE 537

537 Figure I 13. Compliance versus time plot for DSR creep test of adhesive B at different temperatures Figure I 14. Shifted master compliance curve for adhesive B using 43C as a reference temperature

PAGE 538

538 Figure I 15. Comparison between predicted compliance from the DSR creep test and the sustained load creep tests on dogbone samples for adhesive B Figure I 16. Compliance versus time for the DSR creep test of adhesive B at different stress levels

PAGE 539

539 Figure I 17. Shifted master compliance curve for adhesive B using 72.5 psi (0.5 MPa) as the reference stress Figure I 18. Shifted factor as a function of compliance for each pair of compliance creep curves for adhesive B at different stresses for short term DSR creep tests

PAGE 540

540 Figure I 19. Shifted factor for adhesive B as a function of compliance for each pair of compliance creep curves at different stresses for the sustained load creep drawn in blue semi log plot. The linear fit of each curve is shown in green.

PAGE 541

541 Figure I 20. Difference in stress vs. the slope of the fit for each of the plots from Figure I 19. The red line is a linear fit to the data. R2 = 0.909. Figure I 21. Compliance versus time for DSR creep test of adhesive C at different temperatures

PAGE 542

542 Figure I 22. Shifted master compliance curve for adhesive C using 43C as reference temperature Figure I 23. Comparison between predicted compliance from the DSR creep test and sustained load creep tests o n dogbone specimens for adhesive C

PAGE 543

543 Figure I 24. Comparison between predicted compliance from the DSR creep test and sustained load creep tests on dogbone specimens for adhesive C with higher curing temperature

PAGE 544

544 APPENDIX J EARLY AGE CONCRETE I NVESTIGATION SHORT TERM TEST RESULTS The following tables and figures present the short term test results conducted at the University of Stuttgart on the effect of early age concrete in the short term bond strength. In the tables and figures, the short term tests are identified as DDD A ST R, where: DDD: Day of testing (D04, D07, D14, D21, D28) A: Signifies the adhesive type (A, B, or C) ST: Signifies short term test R: Test repetition number (1 5) Table J1 Early age concrete short term anchor pullout test results failure loads Test Test r epetition (kips) 1 2 3 4 5 D04 A ST 9.0 10.1 10.9 10.5 10.9 D04 B ST 17.5 18.7 17.8 16.9 17.1 D04 C ST 14.6 6.7 6.7 10.6 7.2 D07 A ST 11.1 10.4 12.4 11.7 11.4 D07 B ST 19.3 18.3 18.1 17.2 17.5 D07 C ST 15.8 14.4 13.9 14.6 16.6 D14 A ST 13.0 13.3 13.5 14.6 14.5 D14 B ST 20.1 22.6 20.7 13.8 18.6 D14 C ST 15.3 15.1 15.3 16.3 14.8 D21 A ST 11.4 13.3 15.2 13.7 13.8 D21 B ST 18.9 20.2 19.9 20.9 19.9 D21 C ST 14.5 14.4 11.3 1.1 13.2 D28 A ST 13.2 11.5 14.4 14.6 12.7 D28 B ST 16.9 18.2 18.7 17.0 16.4 D28 C ST 17.5 17.6 1.9 14.0 5.6

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545 Table J2 Early age concrete short term anchor pullout test results failure stresses Table J3 Early age concrete short term anchor pullout test results failure displacements Test Test r epetition (in) 1 2 3 4 5 D04 A ST 0.100 0.065 0.146 0.071 0.028 D04 B ST 0.036 0.038 0.034 0.036 0.039 D04 C ST 0.021 0.020 0.029 0.019 0.028 D07 A ST 0.083 0.096 0.070 0.028 0.042 D07 B ST 0.029 0.030 0.029 0.029 0.032 D07 C ST 0.020 0.019 0.017 0.018 0.019 D14 A ST 0.029 0.089 0.033 0.031 0.028 D14 B ST 0.034 0.036 0.028 0.024 0.030 D14 C ST 0.016 0.015 0.016 0.018 0.017 D21 A ST 0.023 0.027 0.034 0.029 0.033 D21 B ST 0.029 0.037 0.034 0.037 0.032 D21 C ST 0.015 0.016 0.016 0.020 0.018 D28 A ST 0.082 0.025 0.034 0.049 0.032 D28 B ST 0.038 0.029 0.029 0.027 0.024 D28 C ST 0.019 0.020 0.024 0.025 0.022 Test Test r epetition (ksi) 1 2 3 4 5 D04 A ST 1.80 2.13 2.33 2.26 2.38 D04 B ST 3.80 3.96 3.82 3.61 3.70 D04 C ST 3.17 1.44 1.40 2.29 1.53 D07 A ST 2.24 2.05 2.58 2.50 2.35 D07 B ST 4.08 3.92 3.87 3.69 3.80 D07 C ST 3.38 3.13 2.95 3.17 3.50 D14 A ST 2.75 2.62 2.86 3.05 3.07 D14 B ST 4.15 4.71 4.32 2.87 3.84 D14 C ST 3.20 3.12 3.19 3.36 3.08 D21 A ST 2.38 2.84 3.29 2.93 2.99 D21 B ST 4.10 4.33 4.37 4.47 4.25 D21 C ST 3.10 3.11 2.41 0.24 2.82 D28 A ST 2.78 2.49 3.01 3.08 2.72 D28 B ST 3.61 3.89 4.06 3.63 3.46 D28 C ST 3.74 3.77 0.40 2.95 1.20

PAGE 546

546 Figure J1 Early age concrete s hort term load versus displacement results for adhesive A at 4 days Figure J2 Early age concrete short term stress versus displacement results for adhesive A at 4 days

PAGE 547

547 Figure J3 Early age concrete short term load versus displacement results for adhesive B at 4 days Figu re J4 Early age concrete short term stress versus displacement results for adhesive B at 4 days

PAGE 548

548 Figure J5 Early age concrete short term load versus displacement results for adhesive C at 4 days Figure J6 Early age concrete short term stress versus displacement results for adhesive C at 4 days

PAGE 549

549 Figure J7 Early age concrete short term load versus displacement results for adhesive A at 7 days Figure J8 Early age concrete short term stress versus displacement resul ts for adhesive A at 7 days

PAGE 550

550 Figure J9 Early age concrete short term load versus displacement results for adhesive B at 7 days Figure J10. Early age concrete short term stress versus displacement results for adhesive B at 7 days

PAGE 551

551 Figure J11. Early age concrete short term load versus displacement results for adhesive C at 7 days Figure J12. Early age concrete short term stress versus displacement results for adhesive C at 7 days

PAGE 552

552 Figure J13. Early age concrete short term load versus displacement results for adhesive A at 14 days Figure J14. Early age concrete short term stress versus displacement results for adhesive A at 14 days

PAGE 553

553 Figure J15. Early age concrete short term load versus displacement results for adhesive B at 14 days Figure J16. Early age concrete short term stress versus displacement results for adhesive B at 14 days

PAGE 554

554 Figure J17. Early age concrete short term load versus displacement results for adhesive C at 14 days Figure J18. Early age concrete short term stress versus displacement results for adhesive C at 14 days

PAGE 555

555 Figure J19. Early age concrete short term load versus displacement results for adhesive A at 21 days Fig ure J20. Early age concrete short term stress versus displacement results for adhesive A at 21 days

PAGE 556

556 Figure J21. Early age concrete short term load versus displacement results for adhesive B at 21 days Figure J22. Early age concrete short term stress versus displacement results for adhesive B at 21 days

PAGE 557

557 Figure J23. Early age concrete short term load versus displacement results for adhesive C at 21 days Figure J24. Early age concrete short term stress versus displacement results for adhesive C at 21 days

PAGE 558

558 Figure J25. Early age concrete short term load versus displacement results for adhesive A at 28 days Figure J26. Early age concrete short term stress versus displacement results for adhesive A at 28 days

PAGE 559

559 Figure J27. Early age concrete short term load versus displacement results for adhesive B at 28 days Fig ure J28. Early age concrete short term stress versus displacement results for adhesive B at 28 days

PAGE 560

560 Figure J29. Early age concrete short term load versus displacement results for adhesive C at 28 days Figure J30. Early age concrete short term stress versus displacement results for adhesive C at 28 days

PAGE 561

561 LIST OF REFERENCES AASHTO (2007a) Standard Specification for Epoxy Resin Adhesives M 235M/M 23503, American Association of State Highway Officials, Washington, DC. AASHTO (2007b) Standard Method of Test for Linear Coefficient for Shrinkage on Cure of Adhesive Systems, T 33307 American Association of State Highway Officials, Washington, DC. AASHTO (2008). Standard Specifications for Transportation Materials and Methods of Sampling and Testing, 28th edition, American Association of State Highway Officials, Washington, DC. AASHTO (2009). Standard Specifications for Structural Supports for Highway Signs, Luminaires and Traffic Signals, 5th edition, American Association of State Highway Officials, Washington, DC. AASHTO (2010a) LRFD Bridge Construction Specifications 2nd edition, American Association of State Highway Officials, Washington, DC. AASHTO (2010b) LRFD Bridge Design Specifications 4th edition, American Association of State Highway Officials, Washington, DC. AASHTO (2010c) Standard Method of Test for Evaluati on of Adhesive Anchors in Concrete under Sustained Loading Conditions TP 84 10, American Association of State Highway Officials, Washington, DC. ACI 318 11 (2011a) Building Code Requirements for Structural Concrete, American Concrete Institute, Farmington Hills, MI. ACI 355.411 (2011b) Qualification of Post Installed Adhesive Anchors, American Concrete International, Farmington Hills, MI. ACI 355.2 07 (2007) Qualification of Post Installed Mechanical Anchors in Concrete, American Concrete Institute, Farmington Hills, MI. ACI 503.5R 92 (1997) Guide for the Selection of Polymer Adhesives with Concrete, American Concrete Institute, Farmington Hills, MI. Adams, R.D. and Wake, W.C. (1984) Structural Adhesive Joints in Engineering, Elsevier Applied Science Publishers, London and New York, pp. 160 162. Anderson, D.S. (1999) The Effects of Permeability and Water Content on the AdhesiveBond Strength Between Epoxy Products and Concrete. High Honors Research Report, University of Florida, Gainesville, FL.

PAGE 562

562 ANS I B212.15.1994 (1994). American National Standard for Cutting Tools CarbideTipped Masonry Drills and Blanks for Carbide Tipped Masonry Drills American National Standards Institute, Washington, DC. ASTM A36 (2008). Standard Specification for Carbon Struct ural Steel American Society for Testing and Materials, West Conshohocken, PA. ASTM A193 (2012). Standard Specification for Alloy Steel and Stainless Steel Bolting for High Temperature or High Pressure Service and Other Special Purpose Applications Americ an Society for Testing and Materials, West Conshohocken, PA. ASTM A307 (2010). Standard Specification for Carbon Steel Bolts and Studs, 60 000 PSI Tensile Strength, American Society for Testing and Materials, West Conshohocken, PA. ASTM A354 (2011). Standard Specification for Quenched and Tempered Alloy Steel Bolts, Studs, and Other Externally Threaded Fasteners American Society for Testing and Materials, West Conshohocken, PA. ASTM A568 (2009) Standard Specification for Steel, Sheet, Carbon, Struct ural, and High Strength, Low Alloy, Hot Rolled and ColdRolled, General Requirements for American Society for Testing and Materials, West Conshohocken, PA. ASTM A615 (2009) Standard Specification for Deformed and Plain CarbonSteel Bars for Concrete Reinforcement American Society for Testing and Materials, West Conshohocken, PA. ASTM C39 (2012). Standard Test Method for Compressive Strength of Cylindrical Concrete Specimens American Society for Testing and Materials, West Conshohocken, PA. ASTM C496 (2011). Standard Test Method for Splitting Tensile Strength of Cylindrical Concrete Specimens American Society for Testing and Materials, West Conshohocken, PA. ASTM C805 (2008). Standard Test Method for Rebound Number of Hardened Concrete, American Soci ety for Testing and Materials, West Conshohocken, PA. ASTM C881/C881M (2002) Standard Specification for Epoxy Resin Base Bonding Systems for Concrete, American Society for Testing and Materials, West Conshohocken, PA. ASTM C882 (2005), Standard Test Method for Bond Strength of Epoxy Resin Systems Used With Concrete by Slant Shear American Society for Testing and Materials, West Conshohocken, PA.

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563 ASTM D471 (2006) Standard Test Method for Rubber Property Effect of Liquids American Society for Testing and Materials, West Conshohocken, PA. ASTM D638 (2008) Standard Test Method for Tensile Properties of Plastics American Society for Testing and Materials, West Conshohocken, PA. ASTM D1151 (2006) Standard Practice for Effect of Moisture and Temperature on A dhesive Bonds, American Society for Testing and Materials, West Conshohocken, PA. ASTM D1875 (2008) Standard Test Method for Density of Adhesives in Fluid Form American Society for Testing and Materials, West Conshohocken, PA. ASTM D2556 (2005) Standard Test Method for Apparent Viscosity of Adhesives Having Shear Rate Dependent Flow Properties American Society for Testing and Materials, West Conshohocken, PA. ASTM D2990 (2001) Standard Test Methods for Tensile, Compressive, and Flexural Creep and CreepRupture of Plastics American Society for Testing and Materials, West Conshohocken, PA. ASTM D7290 (2011) Standard Practice for Evaluating Material Property Characteristic Values for Polymeric Composites for Civil E ngineering Structural Applications Ame rican Society for Testing and Materials, West Conshohocken, PA. ASTM E119 (2008) Standard Test Methods for Fire Tests of Building Construction and Materials, American Society for Testing and Materials, West Conshohocken, PA. ASTM E488 (2003) Standard Test Methods for Strength of Anchors in Concrete and Masonry Elements, American Society for Testing and Materials, West Conshohocken, PA. ASTM E1252 (2007) Standard Practice for General Techniques for Obtaining Infrared Spectra for Qualitative Analysis American Society for Testing and Materials, West Conshohocken, PA. ASTM E1 512 (2001) Standard Test Methods for Testing Bond Performance of Bonded Anchors, American Society for Testing and Materials, West Conshohocken, PA. ASTM F1080 (2008) Standard Test Method for Determining the Consistency of Viscous Liquids Using a Consistometer American Society for Testing and Materials, West Conshohocken, PA. BS 1881 (1996). Testing Concrete Part 208: Recommendations for t he determination of the initial surface absorption of concrete, British Standards Institution, London. Caldwell, D. (2001) Surface Chemical Analysis of Aggregate, Polymer Solutions Incorporated, Blacksburg, VA.

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564 CALTRANS (2001) Method for Testing Creep Performance of Concrete Anchorage Systems, CTM 681 California Department of Transportation, Sacramento, CA. CALTRANS (2006a) Method for Determination of Rheological Properties of Chemical Adhesives using a Dynamic Shear Rheometer CTM 438, California Department of Transportation, Sacrame nto, CA. CALTRANS (2006b) Standard Specifications California Department of Transportation, Sacramento, CA. Chin, J., Hunston, D., and Forster, A. (2007) ThermoViscoelastic Analysis of Ambient Cure Epoxy Adhesives used in Construction Applications, NIST IR 7429, National Institute of Standards and Technology, Washington, DC. Cognard, P. (2005) Technical Characteristics and Testing Methods for Adhesives and Sealants Handbook of Adhesives and Sealants Vol. 1, Chap. 2, Elsevier, Oxford, UK, pp. 21 99. olak, A. (2001) Parametric Study of Factors Affecting the Pull Out Strength of Steel Rods Bonded into Precast Concrete Panels International Journal of Adhesion and Adhesives 21( 6 ) pp. 487493. olak, A. (2007) Estimation of Ultimate Tension Load o f Methylmethacrylate Bonded Steel Rods into Concrete. International Journal of Adhesion and Adhesives 27( 8 ) pp. 653660. Cook, R.A., Doerr, G.T., and Klingner, R.E. (1993). Bond Stress Model for Design of Adhesive Anchors, ACI Structural Journal 90(5 ), pp. 514 524. Cook, R.A., Bishop, M.C., Hagedoorn, H.S., Sikes, D.E., Richardson, D.S., Adams, T.L., and DeZee, C.T. (1994) Adhesive Bonded Anchors: Bond Properties and Effects of in Service and Installation Conditions, Structures and Materials Research Report No. 942, University of Florida, Gainesville, FL. Cook, R.A., Konz, R.C., and Richardson, D.S. (1996) Specifications for AdhesiveBonded Anchors and Dowels, Structures and Materials Research Report No. 963, University of Florida, Gainesville, FL. Cook, R.A., Kunz, J., Fuchs, W., and Konz, R.C. (1998) Behavior and Design of Single Adhesive Anchors Under Tensile Load in Uncracked Concrete. ACI Structural Journal 95 ( 1 ) pp. 926. Cook, R.A. and Konz, R.C. (2001) Factors Influencing Bond Strengt h of Adhesive Anchors ACI Structural Journal 98 ( 1 ) pp. 76 86. Cook, R.A. and Jain, P. (2005) Effect of Coarse Aggregate on the Strength of AdhesiveBonded Anchors, Structures and Materials Research Report No. 051, University of Florida, Gainesville, FL.

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565 Crawford, R.J. (1998) Mechanical Behaviour of Plastics Plastics Engineering, Chap. 2, Elsevier ButterworthHeinemann, Oxford, UK and Burlington, MA. DIN 4240 (1962). Kugelschlagprfung von Beton mit dichtem Gefge Richtlinien fr die Anwendung, Deutsches Institut fr Normung, Berlin. DIN EN 206 1 (2001). Concrete Part 1: Specification, performance, production and conformity, Deutsches Institut fr Normung, Berlin. DIN EN 12390 3 (2009). Testing hardened concrete Part 3: Compressive strength of test specimens Deutsches Institut fr Normung, Berlin. DIN EN 12390 6 (2010). Testing hardened concrete Part 6: Tensile splitting strength of test specimens Deutsches Institut fr Normung, Berlin. Dusel, J.P. and Mir, A.A. (1991) Initial Evaluation of Epoxy Cartridges used for Anchoring Dowels into Hardened Concrete, Minor Research Report F91TL01, California Department of Transportation, Sacramento, CA. Eligehausen, R. and Balogh, T. (1995) Behavior of Fasteners Loaded in Tension in Cracked Reinfor ced Concrete ACI Structural Journal 9 2( 3 ) pp. 365379. Eligehausen, R., Cook, R.A., and Appl, J. (2006a) Behavior and Design of Adhesive Bonded Anchors ACI Structural Journal 103 ( 6 ) pp. 82231. Eligehausen, R., Mallee, R., and Silva, J.F. (2006b) Anch orage in Concrete Construction, Ernst & Sohn, Berlin, Germany, pp. 186. Eligehausen, R. and Silva, J. (2008) The Assessment and Design of Adhesive Anchors in Concrete for Sustained Loading, < http://www.us.hilti.com/fstore/holus/techlib/docs/technical%20publications/anch oring/hiltiadhesivesustainedloading.pdf > (Jun. 11, 2012) EN ISO 6988 (1995) Metallic and Other Non Organic Coatings. Sulfur Dioxide Test with General Condensation of Moisture, International Organization for Standardization, Geneva, Switzerland. EOTA (1997a) Anchors in General ETAG 001 Guideline for European Technical Approval of Metal Anchors for Use in Concrete, Part 1, European Organisation for Technical Approvals, Brussels. EOTA (1997b) Design Methods for Anchorages ETAG 001 Guideline for European Technical Approval of Metal Anchors for Use in Concrete, Annex C, European Organisation for Technical Approvals, Brussels. EOTA (2002) Bonded Anchors ETAG 001 Guideline for European Technical Approval of Metal Anchors for Use in Concrete, Part 5, European Organisation for Technical Approvals, Brussels.

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566 FDOT (2000) Anchor System Tests for Adhesive Bonded Anchors and Dowels FM 5 568, Florida Department of Transportation, Tallahassee, FL. FDOT (2007) Standard Specifications for Road and Bridge Construction, Florida Department of Transportation, Tallahassee, FL. FDOT (2009) Structures Design Guidelines Florida Department of Transportation, Tallahassee, FL. fib (2011) Des ign of Anchorages in Concrete, Federation Internationale du Beton, Lausanne, Switzerland. Fuchs, W., Eligehausen, R., and Breen, J.E. (1995) Concrete Capacity Design (CCD) Approach for Fastening to Concrete. ACI Structural Journal 92 ( 1 ) pp. 7394. Hun ston, D.T., Carter, W., and Rushford, J.L. (1980) Mechanical Behavior of Plastics Mechanical Properties of Solid Polymers as Modeled by a Simple Epoxy Chap. 4, Elsevier ButterworthHeinemann, Oxford, UK and Burlington, MA. Hunston, D. and Chin, J. (2008) Characterization of Ambient Cure Epoxies used in the "Big Dig" Ceiling Collapse, seminar for Virginia Tech Macromolecular Science and Engineering Department, Nov. 5, 2008. ICCES AC58 (2005) Acceptance Criteria for Adhesive Anchors in Concrete and Ma sonry Elements ICC Evaluation Services, Inc., Whittier, CA. ICCES AC58 (2007) Acceptance Criteria for Adhesive Anchors in Masonry Elements, ICC Evaluation Services, Inc., Whittier, CA. ICCES AC308 (2008) Acceptance Criteria for Post Installed Adhesive Anchors in Concrete, ICC Evaluation Services, Inc., Whittier, CA. IDOT (2007a) Laboratory Test Procedure for Chemical Adhesives, Illinois Department of Transportation, Springfield, IL. IDOT (2007b) Standard Specifications for Road and Bridge Construction, Illinois Department of Transportation, Springfield, IL. IDOT (2008) Bridge Manual Illinois Department of Transportation, Springfield, IL. ISO/IEC 17011 (2004) Conformity Assessment -General Requirements for Accreditation Bodies Accrediting Conformi ty Assessment Bodies, International Organization for Standardization, Geneva, Switzerland. ISO/IEC 17020 (1998) General Criteria for the Operation of Various Types of Bodies Performing Inspection, International Organization for Standardization, Geneva, Sw itzerland.

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567 Jazouli, S., Luo, W., Bremand, F., VuKhanh, T. (2005) Application of Time stress Equivalence to Nonlinear Creep of Polycarbonate, Polymer Testing. Polymer Testing, 24, pp. 463467. Klompen, E.T.J., Engels, T.A.P., van Breemen, L.C.A., Schreu rs, P.J.G., Govaert, L.E., and Meijer, H.E.H. (2005) Quantitative Prediction of Long Term Failure of Polycarbonate. Macromolecules 38, pp. 70097017. Krishnamurthy, K. (1996) Development of a Viscoplastic Consistent Tangent FEM Model with Application s to AdhesiveBonded Anchors Ph.D. d issertation, University of Florida, Gainesville, FL. Lee, H.N., Paeng, K., Swallen, S.F., Ediger, M.D. (2009) Direct Measurement of Molecular Mobility in Actively Deformed Polymer Glasses Science 323, pp. 231234. Mehta, P.K. and Montiero, J.M. (2006) Concrete Microstructure, Properties, and Materials McGraw Hill. New York, NY. pp. 66. Messler, R.W. (2004) Joining of Materials and Structures, Elsevier Butterworth Heinemann, Oxford, UK. Meszaros, J. (1999) Trag verhalten Von Verbunddbeln Im Unger issenen Und Gerissenen Beton Ph.D. dissertation University of Stuttgart, Stuttgart, Germany, (in German). McVay, M., Cook, R.A., Krishnamurthy, K. (1996) Pullout Simulation of Postinstalled Chemically Bondaed Anchor s. Journal of Structural Engineering, ASCE, 122(9), 10161024. MDOT (2003) Standard Specifications for Construction, Michigan Department of Transportation, Lansing, MI. MDOT (2005) Bridge Design Manual, Michigan Department of Transportation, Lansing, MI. MDOT (2008) Moratorium on the use of Adhesive Anchors in Sustained TensileLoadOnly Overhead Applications Bureau of Highway Instructional Memorandum 200807, Michigan Department of Transportation, Lansing, MI. MDOT (2009). Materials Source Guide, Michigan Department of Transportation, Lansing, MI. NCHRP (2002) FatigueResistant Design of Cantilevered Signal, Sign, and Light Supports Report 469, Transportation Research Board, Washington DC. NCHRP ( 2009) Adhesive Anchors in Concrete Under Sustained Loading Conditions Report 639, Transportation Research Board, Washington DC.

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568 NTSB (2007a) Ceiling Collapse in the Interstate 90 Connector Tunnel, Boston, Massachusetts, July 10, 2006, Report HAR07/02, National Transportation Safety Board, Washington, DC. NTSB (2007b) Materials Laboratory Factual Report, Report No. 06 105, National Transportation Safety Board, Washington, DC. NYSDOT (2008a) Bridge Manual 4th Edition, (1st US Customary Edition), New York State Department of Transportation, Albany, NY. NYSDOT (2008b) Anchoring Materials Chemical Curing, NTSB Safety Recommendations, Engineering Instruction EI 08012 New York State Department of Transportation, Albany, NY. NYSDOT (2008c) Standard Specifications with January 2009 amendments, New York State Department of Transportation, Albany, NY. PENNDOT (2007) Design Manual Part 4 Structures Publication No. 15M, Vol. 1, Pennsylvania Department of Transportation, Harrisburg, PA. Rodden, R. (2006) Analytical Modeling of Environmental Stresses in Concrete Slabs M S. t hesis, University of Illinois at Urbana Champaign, Urbana, IL. SEAOSC (1997) Standard Method of Cyclic (Reversed) Load Test for Anchors in Concrete or Grouted Masonry Structur al Engineers Association of Southern California, Whittier, CA. Stone, D.C. and Ellis, J. (2006) Stats Tutorial Errors in the Regression Equation < http://www.chem.utoronto.ca/coursenotes/analsci/StatsTutorial/ErrRegr.html > (Jun. 11, 2012) TxDOT (2004) Standard Specifications for Construction and Maintenance of Highways, Streets, and Bridges Texas Department of Transportation, Austin, TX. TxDOT (2007a) DMS 6100 Epoxies and Adhesives Departmental Material Specifications Texas Department of T ransportation, Austin, TX. TxDOT (2007b) Testing Epoxy Materials Tex 614J, Texas Department of Transportation, Austin, TX. VDOT (2007) Road and Bridge Specifications, Virginia Department of Transportation, Richmond, VA. VDOT (2008) Adhesive Anchors f or Structural Applications Instructional and Informational Memorandum IIM S&B76.2, Structure and Bridge Division, Virginia Department of Transportation, Richmond, VA.

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569 Vuoristo, T. and Kuokkala, V. (2002) Creep, Recovery and High Strain Rate Response of Soft Roll Cover Materials Mechanics of Materials 34 ( 8 ) pp. 493 504. Weber, J.W. (1979) Empirical formulas for describing the strength development and the development of the modulus of elasticity of concrete. Betonwerk + Fertigteil Technik 12, pp. 753 756. Wheeler, A., and Ganji, A. (2004) Introduction to Engineering Experimentation, 2nd ed. Prentice Hall, Upper Saddle River, NJ. WSDOT (2008a) Bridge Design Manual Publication M2350.02, Washington State Department of Transportation, Olympia, WA. WSDOT (2008b) Standard Specifications Publication M4110, Washington State Department of Transportation, Olympia, WA. WSDOT (2009) Construction Manual Publication M4101.07, Washington State Department of Transportation, Olympia, WA.

PAGE 570

570 BIOGRAPHICAL SKETCH Todd M. Davis was born in 1972 in Fayetteville, NC. During his childhood, he moved every two to three years and grew up in many places in the USA and Europe. Following graduation from high school in Mannheim, Germany in 1990, Todd enr olled in engineering at Auburn University where he met and married his wife Shana Wise who was a fellow civil engineering classmate. Following graduation from Auburn in 1995 with a B achelors in Civil Engineering, Todd worked as a civil engineer in California. In 1999, Todd and his wife moved to Guatemala to build a vocational school and to open and direct a regional office for a nonprofit engineering organization serving Mexico, Central America, and the Caribbean. In 2007 Todd began his graduate s tudies in structural engineering at the University of Florida. His masters and doctoral research both addressed sustained load performance of adhesive anchors in concrete. During his tenure at the University of Florida, Todd spent a summer in Stuttgart, Germany on a DAAD research grant. Todd is a registered professional engineer (PE) in the state of Florida and following graduation he will be an assistant professor of civil engineering at the Milwaukee School of Engineering (MSOE) in Milwaukee, Wisconsin. Outside of his graduate studies, Todd enjoys biking, hiking, and backpacking. Having lived overseas for a significant time, Todd and his wife enjoy traveling as well as welcoming internationals into their home, learning about their home countries, and help ing them to assimilate to life in the US.