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Evaluating Nondestructive Testing Techniques to Detect Voids in Bonded Post-Tensioned Concrete Ducts

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Title:
Evaluating Nondestructive Testing Techniques to Detect Voids in Bonded Post-Tensioned Concrete Ducts
Creator:
ANDARY, ELIE GEORGE ( Author, Primary )
Copyright Date:
2008

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Subjects / Keywords:
Acoustic ducts ( jstor )
Corrosion ( jstor )
Nondestructive testing ( jstor )
Signals ( jstor )
Steels ( jstor )
Surface waves ( jstor )
Tomography ( jstor )
Ultrasonics ( jstor )
Ultrasonography ( jstor )
Velocity ( jstor )

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University of Florida
Holding Location:
University of Florida
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Copyright Elie George Andary. Permission granted to the University of Florida to digitize, archive and distribute this item for non-profit research and educational purposes. Any reuse of this item in excess of fair use or other copyright exemptions requires permission of the copyright holder.
Embargo Date:
8/1/2008
Resource Identifier:
78824088 ( OCLC )

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EVALUATING NONDESTRUCTIVE TESTING TECHNIQUES TO DETECT VOIDS IN BONDED POST-TENSIONED DUCTS By ELIE GEORGE ANDARY A THESIS PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLOR IDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE IN BUILDING CONSTRUCTION UNIVERSITY OF FLORIDA 2003

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ACKNOWLEDGMENTS I would like to express my gratitude to all those who gave me the possibility to complete this thesis. I feel a deep sense of gratitude for my parents, Asma and George, who formed part of my vision and taught me the good things that really matter in life. Their presence and prayer still provide a permanent inspiration for my journey in this life. I am grateful for my brother, Nazih, and for my sisters, Nadine and Aline, for rendering me the sense and the value of brotherhood. I am glad to be one of them. I want to thank the College of Design, Construction, and Planning, and especially the Rinker School of Building Construction with its faculty members and staff for giving me the opportunity to commence this thesis and to do the necessary research work. I am deeply indebted to my advisor Dr. R. Raymond Issa, whose help, stimulating suggestions, and encouragement helped me in accomplishing my master’s degree. I wish to express my gratitude to my committee chairman, Dr. Larry Muszynski, for reviewing the manuscript of this thesis, and being helpful with comments and answering questions. Moreover, I am very grateful for the support and experience that Dr. Abdol Chini provided and for his valuable discussions. This research has been supported and funded by the Florida Department of Transportation; sincere thanks go to the State of Florida’s engineers for their guidance, support and encouragement. I want to thank my colleagues for all their help, support, interest, and valuable hints, especially Mr. Antoine Faddoul, Mr. Uluc Bayar, Mr. Francisco Monteallegre, Mr. Mathew Harris, and Mr. Vali Tirsoaga. ii

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TABLE OF CONTENTS page ACKNOWLEDGMENTS. ii LIST OF TABLES. vi LIST OF FIGURES.. vii ABSTRACT....x CHAPTER 1 INTRODUCTION.. 1 Statement of Problem ................................................................................................1 Objective of the Study ...............................................................................................3 2 LITERATURE REVIEW... 4 Introduction ...............................................................................................................4 Ultrasonic Tomography Theory ................................................................................4 Tomographic Survey Instrumentations and Experimental Procedure .......................5 Reflection Seismology ...............................................................................................5 Infrared Thermography .............................................................................................7 Titman’s General Principles ......................................................................................8 Spectral Analysis or Ultrasonic Signals ....................................................................9 Ultrasonic Testing ...................................................................................................10 New Ultrasound and Sound Generation Methods ...................................................11 New Methods for Stress Wave Generation in Concrete ..........................................14 Inquiring Agency NDT&E Techniques ..................................................................16 Mechanical Wave Techniques (MWT) ...................................................................16 Electromagnetic Microwave Techniques (EMT) ....................................................17 Optical Techniques (OT) .........................................................................................18 Other Techniques .....................................................................................................19 Split Spectrum Processing .......................................................................................20 Acoustic Tomographic Imaging of Concrete Infrastructure ...................................22 Radar ...................................................................................................................27 Impact-Echo ............................................................................................................28 Ultrasonic Pulse Echo, A-scan ................................................................................28 Ultrasonic Pulse Array ............................................................................................29 iii

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Ultrasonic Pulse Echo, B-scan................................................................................29 Ultrasonic Pulse Echo, B-scan, LSAFT ..................................................................30 Ultrasonic Pulse Echo: 2D-Synthetic Aperture and 3D-SAFT...............................30 EFIT Simulation ......................................................................................................31 3 SURVEY OF STATE DEPARTMENTS OF TRANSPORTATION. 34 Introduction .............................................................................................................34 Results of the Survey ...............................................................................................34 4 RESEARCH METHODOLOGY. 39 Introduction .............................................................................................................39 NDT Technologies to be Evaluated ........................................................................40 Materials ..................................................................................................................42 Grout. ...................................................................................................42 Mixing Grout ...........................................................................................................42 Ducts ....................................................................................................................43 Tendons ...................................................................................................................43 5 TEST RESULTS AND DISCUSSION 44 Introduction .............................................................................................................44 PHASE I ..................................................................................................................44 NDT Technologies Evaluated .....................................................................47 Phase I Results ............................................................................................50 PHASE II .................................................................................................................50 Background .................................................................................................52 Impact Echo (IE) Method ...........................................................................52 Spectral Analysis of Surface Waves (SASW) Method ...............................54 Ultasonic Pulse Velocity Tomographic Imaging (UPVT) ..........................59 Phase II Results ...........................................................................................60 PHASE III ...............................................................................................................78 Research Investigation Scope .....................................................................78 Summary of Findings ..................................................................................78 Background .................................................................................................79 Wall Specimen II .......................................................................................79 6 CONCLUSIONS.. 91 Results from IE Scans .............................................................................................91 Results from SASW tests ........................................................................................91 Results from Pulse Velocity UPVT .........................................................................91 Impactechogram ......................................................................................................92 7 RECOMMENDATIONS. 93 iv

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APPENDIX A. SAMPLE SURVEY. 94 B. DATA FROM STATE DEPARTMENTS OF TRANSPORTATION SURVEY... 96 C. TECHNICAL DATA GUIDE.. D. MATERIAL SAFETY DATA SHEET..101 LIST OF REFERENCES... 105 BIOGRAPHICAL SKETCH.. 107 v

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LIST OF TABLES Table page 1-1 Summary of NDT Techniques ...................................................................................32 3-1 Range of Material Quantities for Class A, B, C, and D. ...........................................37 3-2 Nondestructive Inspection Method. ...........................................................................37 3-3 Post-tensioning Failures Experienced by DOTs ........................................................38 5-1 IE Depth Results for Empty Ducts and Solid Concrete. ............................................68 5-2 IE Depth Results for Fully Grouted, Partially Grouted and Empty Ducts. ...............68 5-3 UPVT Velocities in ft/ms for Fully Grouted, Partially Grouted and Empty Ducts. ..77 6-1 Summary of NDT Evaluation ....................................................................................92 vi

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LIST OF FIGURES Figure page 3-1 Results of Post-Tensioning Systems (Bonded and Unbonded) .................................35 3-2 Frequency of Duct Material Used in Post-Tensioning ..............................................35 3-3 Bonded Grout Class Used. .........................................................................................37 4-1 Research Methodology Flow Chart ...........................................................................39 5-1 Grouted Beam Samples .............................................................................................45 5-2 Grout Beam Samples with Defect Locations ............................................................45 5-3 Schematic of Defect Type and Location for Grouted 3-inch Corrugated Metal Duct Samples. ..........................................................................................................46 5-4 Schematic of Defect Type and Location for Grouted 2-inch Corrugated Plastic Duct Samples. ..........................................................................................................46 5-5 Scanning IE Device and Data recorder ......................................................................48 5-6 Close-up of Scanning IE Device Relative to Specimen Size ....................................48 5-7 Static Ultrasonic Tomography (UT) Test ..................................................................49 5-8 UT Test in Progress ...................................................................................................49 5-9 Reinforced Concrete Dimensions and Duct ..............................................................51 5-10 Two Concrete Walls with Steel and Plastic Ducts ..................................................51 5-11 Schematic of Impact Echo Method .........................................................................53 5-12 Freedom Data PC Acquisition System with IE Scanner .........................................54 5-13 The Impact Echo Scanning test ...............................................................................54 5-14 Field Setup for SASW Test .....................................................................................56 vii

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5-15 SASW Test on the Wall...........................................................................................56 5-16 Tomography Test Source and Receiver Combinations at Different Depths .........60 5-17 Nominal Wall Thickness and its IE frequency response from IE Scanning of Solid Concrete ...........................................................................................................61 5-18 IE Thickness Results and Example Frequency Response from the Empty Steel Duct of Wall II (Duct Center Line Scan) ..................................................................62 5-19 IE Thickness Results and Example IE frequency response from the Empty Plastic Duct of Wall II (Duct Centerline Scan) .........................................................63 5-20 IE Thickness and Frequency Results from a Steel Duct – Wall I ...........................65 5-21 Impactechogram of the IE test Results along the Steel Duct ..................................66 5-22 IE Thickness and Example Frequency Results from a Plastic Duct ........................67 5-23 Schematic of compression wave penetration through the ducts. .............................69 5-24 Schematic of compression wave penetration through partially grouted ducts. .......70 5-25 Impactechogram of Frequency Data from a Plastic Duct ........................................70 5-26 IE Thickness Results from IE Scanning off the Center Line of Steel Duct ............71 5-27 IE Thickness Results from IE Scanning across Steel and Plastic Ducts – Fully Grouted Ducts ...........................................................................................................72 5-28 IE Thickness Results from IE Scanning across Steel and Plastic Ducts – Partially Grouted Ducts (Debonded) .......................................................................................73 5-29 IE Thickness Results from IE Scanning across Steel and Plastic Ducts – Empty Ducts .........................................................................................................................73 5-30 Surface Wave Velocity Dispersion Curve Results from Steel Duct .......................74 5-31 Surface Wave Velocity dispersion Curve Results from Plastic Duct ......................75 5-32 Velocity Tomogram Image from Fully Grouted Steel and Plastic Ducts ................76 5-33 Velocity Tomogram Image from Partially Grouted (Debonded) Steel and Plastic Ducts .........................................................................................................................76 5-34 Velocity Tomogram Image from Empty Steel and Plastic Ducts ...........................77 viii

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5-35 Data Acquisition System with IE Scanning Device ................................................79 5-36 Reinforced Concrete Dimensions and Duct Location .............................................80 5-37 Concrete Walls with Steel and Plastic Ducts ...........................................................80 5-38 Calibration Scan from Sunday, 12/29/02 ................................................................82 5-39 Calibration Scan from Tuesday, 1/12/03 .................................................................82 5-40 Horizontal Scan from Sunday, 12/29/02 – Day 1 ....................................................83 5-41 Horizontal Scan from Tuesday, 1/21/03 – Day 24 ..................................................84 5-42 Scan along Steel duct from Sunday, 12/29/02 – Day 1 ...........................................85 5-43 Scan along Steel duct from Tuesday, 1/21/03 – Day 24 .........................................85 5-44 Scan along Plastic duct from Sunday, 12/29/02 – Day 1 ........................................86 5-45 Scan along Plastic duct from Tuesday, 1/21/03 – Day 24 .......................................87 5-46 Off Centerline of Steel Duct from 12/29/02 – Day 1 ..............................................88 5-47 Off Centerline of Plastic Duct from 12/29/02 – Day 1 ............................................88 5-48 Off Centerline of Steel Duct from 1/12/02 – Day 24 ..............................................89 5-49 Off Centerline of Plastic Duct from 1/21/03 – Day 24 ...........................................90 ix

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Abstract of Thesis Presented to the Graduate School of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Master of Science in Building Construction EVALUATIONG NONDESTRUCTINE TESTING TECHNIQUES TO DETECT VOIDS IN BONDED POST-TENSIONED DUCTS By Elie George Andary August 2003 Chairman: Larry Muszynski Cochair: R. Raymond Issa Major Department: Rinker School of Building Construction The use of post-tensioning in bridges can provide durability and structural benefits to the system in the construction field. In bonded post-tensioned construction, Portland cement grout is used to form a sheath around the steel tensioning strand, and act as a solid impermeable barrier to prevent the ingress of chlorides from reaching the steel and initiating corrosion. Too often, voids are formed in the post-tensioning duct from incomplete grouting, trapped air pockets, or from evaporation of bleed water due to poor grout design or poor grouting procedures or both. Tendons are subjected to large tensile stress; tendon failure due to corrosion may result in the failure of the concrete member, leading to severe damage for the whole structure that might lead to a disaster. That is why those types of structures need to be adequately tested to ensure acceptable performance during their service life. x

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There are three non destructive testing (NDT) techniques that were evaluated in this research: Impact Echo (IE), Spectral Analysis of Surface Waves (SASW), and Ultrasonic Pulse Velocity Tomography (UPVT). Impact Echo has been used successfully since the end of 1980s to detect cracks or defects in concrete slabs or beams. The method has been also used to detect voids versus grouted conditions inside of bonded post-tensioned ducts where the ducts are metal. The Spectral Analysis of Surface Waves (SASW) method uses the dispersive characteristics of surface waves to determine the variation of the shear wave velocity (stiffness) of layered system with depth. The SASW method can be performed on any material provided an accessible surface is available for receiver mounting and impacting. Materials that can be tested with SASW include concrete, asphalt, soil, rock, masonry, and wood. Ultrasonic Pulse Velocity Tomography (UPVT) requires access to two sides of a structural element in order to send and receive sound waves at multiple angles above and below ducts that allow images of internal concrete and duct conditions. The tomography tests use two ultrasonic transducers, one as a source and the other as a receiver. Acoustic data are collected for many receiver and source combinations at different depths, and can produce UPV based images of a 2-D or 3-D concrete zone. The results from IE tests showed the most promise for assessing grout conditions of all three tests. The IE method was used successfully to identify internal conditions of a steel duct. For a plastic duct, it was more difficult to identify grout conditions due to partial debonding conditions between the plastic duct and concrete wall and apparent multiple resonant frequencies. xi

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CHAPTER 1 INTRODUCTION The use of post-tensioning in bridges can provide durability and structural benefits to the system while expediting the construction process. However, applying non-destructive testing on the members of the post-tensioning system is vital to the integrity of the structure because loss of post-tensioning can result in catastrophic failure. Usually chloride induced corrosion of steel in concrete is ranked as one of the most costly forms of corrosion. This type of corrosion usually affects coastal substructure elements, exposed to seawater by immersion or spray, and inland bridges may also be at risk due to the application of deicing salts. Statement of Problem Portland cement grout is often used in post-tensioned structures to provide bond between the tendon and the surrounding duct and also as corrosion protection for the tendons. Grout for bonded post-tensioning is a combination of Portland cement and water, along with any admixtures necessary to obtain required properties such as fluidity, thixotropy, and reduced permeability. The grout plays a crucial role in the corrosion protection of the system since it may be the “last line of defense” against chloride attack of the post-tensioning strands; an optimum grout combines desirable fresh properties along with good corrosion protection. 1

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2 Grouts with properties such as fluidity, low permeability, and bleed resistance can provide maximum protection when combined with proper grouting procedures. Voids can be formed in the post-tensioning duct from incomplete grouting, trapped air pockets, or from the evaporation of bleed water pockets. High performance grout is of little benefit if poor grouting procedures result in large void formations, which provide no protection to the strand and no transfer of bond. Proper venting of the post-tensioning duct is critical for complete grouting. The void between the tendon and the post-tensioning duct is a very complex space. For instance, a parabolic shaped duct with a tensioned tendon may have a number of small voids of varying shapes and sizes, and a very stiff grout may not fill the interstices. Bleed lenses can form a result of the separation of water from the cement. This sedimentation process is accentuated by the addition of seven-wire strands, which act as a “water-important mechanism.” The spaces within the individual twisted wires that form the strand are large enough to allow easy passage of water but not cement. Ducts with vertical rises will typically cause more bleed due to the increased pressure within the grout section of the duct exposing the tendon. Even in parabolic draped ducts, any bleed water will tend to gather near the highest intermediate points, leaving voids in the duct. Grouts containing anti-bleed admixture, or thixotropic grouts, can be bleed resistant even when used in ducts with large vertical rises. The grouts are able to retain their water even under high pressures and can eliminate significant void formation when proper grouting procedures are followed.

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3 Objective of the Study The objective of the research contained in this thesis is to evaluate nondestructive testing (NDT) techniques to detect voids in bonded post-tensioned ducts. NDT techniques have been practically used for testing concrete elements, but there is a need to speedup the field test process and improve the analysis procedures of this testing. Moreover, it would be useful to identify the advantages and the disadvantages of each technique and compare the effectiveness and the accuracy of their results and outputs.

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CHAPTER 2 LITERATURE REVIEW Introduction The literature review is divided into one section for each of the methods discussed. Each section addresses one of the techniques used for testing concrete. A brief definition followed by a review and a conclusion of early theories and past research on each characteristic is included in theses sections. This study illustrates a theory and an experimental procedure called the Ultrasonic tomography theory and Tomographic survey instrumentations and experimental procedure. Ultrasonic Tomography Theory The mathematical theory of Ultrasonic Tomography was established by Radon in 1917 in which it is shown that the internal characteristics of an object can be exactly reconstructed by a complete set of projections through the object. The simplest form of tomography is to measure the energy transmitted through the specimen and constructing the section. This can be performed by measuring the times-of-flight of a series of stress pulses along different paths through the specimen. “The basic concept is that the stress pulse on each projection travels through the specimen and interacts with its internal construction. Variations in the internal conditions result in different tunes-of-flight being measured. The tomographic software reconstructs the section by combining the information contained in a series of these projections, 4

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5 obtained at different angles through the section. The greater the number of measurements taken, the more accurate are the results” (Martin et al. 2001). Tomographic Survey Instrumentations and Experimental Procedure Tomographic survey instrumentations and experimental procedures have been widely used to non-destructively test concrete and is robust and therefore suitable for use onsite. The data of measuring the time-of-flight of an ultrasonic pulse, along many ray paths through a section of the beam is then processed using tomographic software and the results are given as a contour plot of velocity across the section (Martin et al. 2001). In conclusion, ultrasonic tomography is a successful method of investigating post-tensioned concrete beams. However, the method is time consuming and so should be used in conjunction with another testing method, such as sonic impact-echo. Moreover, array systems could be developed which would greatly reduce the testing time (Martin et al. 2001). Reflection Seismology Chang et al. (2001) described the theory of reflection seismology. The multi-sources and multi-receivers are distributed on the surface of a two-layer system to generate and pick up the ultrasonic waves, respectively. The distance between the source and receiver is known as offset, and this method requires 48 receivers for each source. The near offset is the distance from source to first receiver and far offset is the distances from source to last receiver. When source 1 is triggered, 48 receivers in spread 1 simultaneously record the reflected echoes from the interface of the two-layer system. After the source 1 shot, the source and all receivers move forward a unit distance, then source 2 is triggered and the 48 receivers in spread 2 record the reflected echoes, and so

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6 forth. The middle point between source 1 and receiver 1 on the interface of the two-layer model is the common depth pointy (CDP) CDP1, and the middle point between source 1 and receiver 2 is the CDP2, and so on. The fold number is defined as the number of time histories having the same CDP and the time histories will be stacked (added) together. In this configuration, the CDP1, and CDP2 have 1-fold and CDP3 has 2-fold. The time histories having different offsets but the same CDP are sorted to a CDP gather which is a side-by-side display of time histories. The normal move out (NMO) is the time difference of the echoes reflected from the CDP between the zero offset measurement (source and receiver located at same point) and some offset measurement. Before stacking the time histories in a CDP gather, the (NMO) corrections for the time histories are required. After stacking, the new time history can be considered as the echoes recorded directly above CDP using the single-probe pulse-echo method. The section is constructed by side-by-side display of the new time histories and contains information of any cracks presented in the concrete (Chang et al. 2001). The advantages of this method are that the signals reflected from the interface will be enhanced and it is not necessary to pick the travel times or the waveform of the reflected echoes for analysis. The necessary data processing can be conducted using a personal computer and the output represents an image of the geometry of the reflecting interface (Chang et al. 2001). The ability of detecting cracks in concrete relies strongly on the capability of the sensing system, techniques, and theories of detection, and signal processing techniques for record data. The ultrasonic system and data processing techniques, demonstrate that horizontal cracks of length 3 cm, depth 6 cm deep and of length 5 cm, depth 14 cm and

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7 an inclined crack with a 15 0 dip angle, 6 cm deep can be imaged successfully. Although not all the cracks in concrete can be detected, some of the small cracks in concrete structures can be detected by the reflection seismology method that other ultrasonic nondestructive methods would miss. However, the more weakness of the echoes reflected (or diffracted) from the crack, the more measurements from different surveying angles (offsets) are required for the stacking process on order to make a correct estimation of the crack. The quality and resolution of the signals can be improved by stacking the measurements after some necessary correction (Chang et al. 2001). Infrared Thermography According to Titman (2001), infrared thermography is a well-established tool in the armory of non-destructive testing (NDT) and monitoring techniques. It can be used to investigate a very broad range of situations where variation in surface temperature may indicate a problem in or a particular property of the material(s) below the surface. The successful application of thermography has become possible due to the development of sophisticated portable thermal imagers, specifically designed for NDT and condition monitoring. In view of its totally non-destructive and non-invasive nature, a thermographic survey may, in general, be very rapidly completed, with minimal access requirements and can therefore be very cost-effective. The 'visual' nature of the output can frequently lead to an immediate interpretation by a skilled practitioner. High winds can reduce the effectiveness of outdoor surveys due to surface temperature shear effects. Similarly, rain may lead to surface cooling, thus masking thermal effects from below the surface. Standing water on roofs must be avoided (Titman 2001).

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8 Titman’s General Principles All bodies above absolute zero temperature emit electromagnetic radiation. Whilst visible light occupies a narrow spectral band (0.4-0.7 m), thermography, as the name implies, utilizes the ability of specialized imagers to detect radiation in the “thermal” part of the infrared spectrum, typically in the 3-5 or 8-14 m windows (Titman 2001). There are three types of conditions necessary for thermography to be useful. These are as follows: Heat (cold) Source An object at depth is hotter (or colder) than the medium in which it is embedded. The corresponding raising (or lowering) in surface temperature directly over this object may enable its location. The temperature of the object (relative to the general surrounding material), together with its depth below the surface, will have a bearing on its detectability or resolution from adjacent similar warm objects (Titman 2001). Thermal Gradient If a stable thermal gradient exists through an element of a structure and there is no significant variation in thermal conductivity of the materials within the element, (then the surface temperature over the warm face should be constant; and similarly for the cool face. Material omission, or local damage within the element, lead to variations in conductivity which are indicated by surface temperature fluctuations (Titman 2001). Induced Heating In the absence of either of the above, application of a hot (or cold) source to a surface will cause the surface to heat up (or cool down) at varying rates and to differing ultimate surface temperatures depending on the thermal resistance (Titman 2001).

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9 As a conclusion, wide range of structural situations has been considered where a thermographic survey can be useful. Whether used in isolation or in combination with other techniques, thermal imaging can prove highly cost effective in view of its speed and the general lack of access requirements compared with other methods. The results, in the hands of a skilled practitioner, can be very graphic and immediate to understand (Titman 2001). Spectral Analysis or Ultrasonic Signals Halabe and Franklin (1999) describe the use of spectral analysis or ultrasonic signals in identifying areas of distress in different construction materials. Despite the success with time domain analysis for certain applications, several researchers have recognized its limitation and suggested the use of frequency domain analysis to enhance the sensitivity and reliability of ultrasonic testing. Horne and Duke have shown the need for using normalized power spectrum to analyze ultrasonic signals shat are dispersive using three case studies. Fast Fourier Transforms (FFT) has been used to characterize wave attenuation in wooden members. Some researchers have stressed the need for frequency domain analysis for crack detection. Also, power spectral density (PSD) analysis has been used to detect cracks in metal plates. Engineers emphasize the use of frequency domain analysis and employs power spectrum analysis in conjunction with time-of-flight measurements to detect flaws in structural materials. The underlying philosophy of the spectral analysis has been discussed along with the necessary measurement conditions. The methodology presented here will greatly help in identifying areas of distress in infrastructures built with various construction materials as in

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10 aluminum, wooden, and composite wrapped concrete members (Halabe and Franklin 1999). Ultrasonic Testing In a study by Yeih and Huang (1998), the amplitude attenuation method in Ultrasonic Testing (UT) was used to evaluate the corrosion damage of reinforced concrete members. It is found that the amplitude attenuation method has good performance in corrosion detection for reinforced concrete members. There exists a consistent relationship between the average amplitude attenuation and the electrochemical parameters such as open circuit potential values, the instantaneous corrosion rate, and thickness loss (Yeih and Huang 1998). UT has not been used in concrete detection as commonly as it has been used in metal detection. The reason for the limited applications of UT in concrete structures is that the penetration depth required in concrete members is usually much longer than that in metal members. For full penetration of ultrasonic wave in RC members, a lower excitation frequency (e.g., 500 KHz) should be used. However, a lower excitation frequency induces longer wave length, so that a loss of resolution may occur. The UT method employs an excited transducer, usually Piezometric Transducer (PZT), to excite a mechanical wave and the mechanical wave propagates inside the object to be detected. A receiver (PZT) is mounted on the other side of the object to receive the signals of this mechanical wave. According to the wave signals, two important parameters, pulse velocity and amplitude, are frequently used to analyze the integrity of the object. The pulse velocity is calculated from dividing the total wave path length by the total flying time it required. When a flaw, like a major crack, is along the wave path, the total flying

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11 time of the wave is longer due to the diffraction of wave. The amplitude attenuation is mainly due to the dispersion and dissipation of wave. In a corroded RC structure, the scattering phenomenon of wave by cracks, the dissipating oscillation due to cracks, and reduction of transmitted wave due to the change of acoustic impedance either from cracks inside the concrete or rust on the concrete-rebar interface result in additional amplitude attenuation compared to an undamaged body (Yeih and Huang 1998). In the UT method, the wave signals reflect information along the wave path. When only a spot is examined, this is called an A-scan. When spots are connected into a line, this is called a B-scan. When the lines of B-scan are combined, information on the examined surface can construct the C-scan. For a 3-D view, the D-scan can be constructed by combining information on all surfaces of the object. Concrete strength was reported to have an empirical relation with UT pulse velocity and the pulse velocity method was used to evaluate cracks in concrete. The average UT amplitude attenuation percentages have been found to have interesting relationships with electromechanical parameters in accelerated corrosion experiments. The average UT amplitude attenuation in the higher strength concrete was easier to detect because of the brittle microstructure. Due to the rebar size effect, specimens with smaller size rebars had more significant UT amplitude attenuation than those with larger size rebars in the beginning stage of corrosion process (Yeih and Huang 1998). New Ultrasound and Sound Generation Methods According to Popovics et al. (1999), transient stress waves used in new ultrasound and sound generation methods offer a powerful approach for non-destructive condition evaluation of concrete structures. However, currently used stress-wave-generating

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12 techniques are limited by poor controllability and/or penetrating ability. Stress wave generation must therefore be improved so that the application of existing and new ultrasonic and sonic non-destructive testing techniques to concrete structures will be more effective. Electromagnetic and piezoelectric based stress wave sources are investigated for potential applicability with existing concrete non-destructive evaluation (NDE) techniques. A suitable stress wave source must be flexible in terms of input signal control, in order to be used with the various non-destructive stress wave techniques. The final signal source must also be effectively applicable to rough surfaces of unprepared concrete structures. In particular, the following characteristics should be considered for each potential stress wave source: (a) Frequency-content control (a frequency range of 1-50 kHz is desired) (b) Control of the magnitude of the .loading force (the source must be able to propagate signals through attenuating material with large path lengths and unprepared surfaces) (c) Wave mode generation (the ability to generate longitudinal-type and/or surface-type waves is desired) (Popovics et al. 1999). At present, two methods are commonly used for the generation of transient stress waves for testing concrete: traditionally excited piezoelectric sources and impact events. Traditional Piezoelectric Excitation Transient ultrasonic waves generated by traditional piezoelectric excitation are a result of the resonance vibration of a piezoelectric crystal, housed within a transducer unit, in direct contact with the inspected concrete structure. The crystal is driven by an electrical signal supplied by an attached pulser-receiver unit; the driving signal typically has the form of a voltage spike and the amplitude can range from 300 to 1000 V. The control of frequency content and pulse length is therefore achieved by changing the

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13 piezoelectric transducer, as each transducer has a characteristic resonant frequency and bandwidth, while the electrical driving signal remains the same. This source type is designed primarily for the inspection of engineering materials other than concrete, and transducers with a relatively high frequency range of 0-25 to 10 MHz are typically utilized. The principal drawback of using traditionally excited piezoelectric transducers as stress wave sources for concrete is the inability to generate controllable and usable signals in the desired frequency range of 150 kHz which may be applied in existing NDE techniques (Popovics et al. 1999). Impact The use of mechanical impact, such as a single ball drop or hammer strike, as a source of transient stress waves for specific non-destructive tests of concrete has been widely used. The technique is popular because relatively large stress wave energies may be easily generated. Since the character of the generated stress wave is primarily a function of the vibration properties of the impactor, the pulse shaping ability (centre frequency and frequency content control) is limited to controlling the impact duration and intensity. Theoretically, the frequency content of the wave action generated by a ball drop on an elastic half-space can be controlled by varying the ball size and drop height, as defined by the Hertz solution for impact; the size of the impacting ball is the most significant factor in controlling the input frequency content. The frequency distribution of impact-generated wave pulses is generally broad, and the frequencies are relatively low-generally below 30 kHz. Control of the generated stress wave field in the material is limited: impact sources generate all wave modes (longitudinal, transverse and surface) with non-planar wave fronts. The principal drawbacks of using impact sources for stress

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14 wave generation in conjunction with concrete-testing techniques are poor signal consistency. Poor signal controllability in terms of frequency content and poor stress wave field directivity control (Popovics et al. 1999). Some of the new methods for stress wave generation in concrete are Frequency-modulated Chirp Driving Signal and Amplitude-modulated Driving Signal. New Methods for Stress Wave Generation in Concrete Frequency-Modulated Chirp Driving Signal The use of piezoelectric-based stress wave sources which are driven with a frequency-modulated (FM) chirp electrical signal in place of a voltage spike has recently been reported for use in concrete testing. In contrast to traditionally excited piezoelectric sources, the characteristics of the electrical driving signal, rather than the resonance of the piezoelectric crystal, primarily determine the character of the resulting stress wave. The advantages of such excitation are improved control of the character of the stress wave in terms of centre frequency and frequency content and increased signal penetrating ability within the frequency region of interest, assuming that the driven source is suitably well behaved in a given frequency region. A drawback of FM chirp signals is the need for an advanced random signal synthesizer to generate the signal (Popovics et al. 1999). Amplitude-Modulated Driving Signal Electrical signals in the shape of amplitude-modulated (AM) sine bursts may also be used to drive the stress wave generators. AM burst-driven sources have the same advantages as those driven by FM chirps. However, sophisticated signal synthesizers are not required to generate AM burst signals. AM burst signals are obtained from two basic waveform generators connected together: one generator, designated as the carrier signal

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15 generator, generates a sine burst (tone burst) of a given frequency and cycle length; the other generator, designated as the modulating signal generator, amplitude-modulates the burst with a sine or ramp function of lower modulating frequency. The only requirements for the signal generators are that the carrier signal generator must have tone burst generation and eternal AM input capabilities and that the modulating signal generator must have an external trigger input capability (Popovics et al. 1999). The following conclusions are drawn on the basis of the data presented in this study. Basic, readily obtainable signal generators and laboratory equipment may be assembled to generate AM-Burst driving signal. Piezoelectric ultrasonic transducers and electromagnetic modal shakers which are driven by AM bursts provide controlled and usable stress wave pulses in the frequency range needed for concrete testing: an appropriate electromagnetic modal shaker provides the lower-frequency signals (below 10KHz), while an appropriate piezoelectric transducer provides the higher range (15=50KHz). Piezoelectric ultrasonic transducers and electromagnetic modal shakers which are driven by amplified AM bursts provide stress waves with sufficient energy to test full sized concrete structures. The versatility of AM-burst driven sources makes them eminently suitable for application to concrete testing techniques such as the impact echo and spectral-analysis-of-surface-waves tests. AM-burst-driven stress wave sources offer excellent frequency-content control and significant noise reduction capability not found in the stress wave sources currently used with concrete test (Popovics et al. 1999). Direct measurement NDT & E techniques can be used to measure the properties of materials and the corrosion state in bridge damage detection directly. These techniques

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16 could be based on various physical parameters. However, a technique is sometimes not suitable for in situ application. In a slightly destructive manner, however, samples could be taken from a bridge by using DS. HCPM can be used for detecting the rate of the corrosion of the steel bars in reinforced concrete. MFL can be used for locating the fracture of steel rebar in reinforced concrete and for detecting the corroded and broken cables for bridge cables (Wang et al. 2001). Inquiring Agency NDT&E Techniques Inquiring agency NDT & E techniques use an inquiring agent as a probe and which can be active or passive. The agent usually is a wave packet. In active techniques, the wave packet is generated by the testing instrument and transmitted into the materials to be tested. The examples are UT and GPR. The probe agent, the wave packet, interacts with the material and the foreign objects if it exists. Then it gives out some signals, which are carrying the information about the specimen. In passive techniques, the wave packet stems from the tested specimen itself and carries the information about the process the specimen is undergoing (Wang et al. 2001). Mechanical Wave Techniques (MWT) MWT takes mechanical waves as the working agency. The principle of these techniques is the generation, propagation and reception of mechanical waves. The wave packet transmitted into the materials to be tested interacts with the material and changes its own parameters, which carries the information about the properties of the tested object. MWT can meet most of requirements for NDT&E in bridge engineering. They are accurate in determining shape, size and depth of the defective areas, with high sensitivity, deep penetration, low cost, easy and fast operation, and convenient for in-situ use.

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17 Working in the ultrasonic band, as an active method, UT can locate and identify defects, fractures, voids and inhomogeneous regions can measure thickness and size of defects, can estimate strength of steel and concrete in bridges. AE is one of the most important passive NDT&E techniques. Due to its passive measurement nature, AE can be applied to measure the object when the loads are actively added on a specimen and to monitor the dynamic behavior of structures such as bridges and buildings. It has been used to measure stress, identify rebar corrosion, locate corrosion position, estimate corrosion rate and monitor the cracking behavior of concrete. It is an extremely powerful technique for evaluating properties of the fracture and corrosion process. Working in the acoustic and low ultrasonic frequency band, as an active method, IE can be used to detect and locate flaws, fractures, voids, and delaminations in bridge deck and girder. It can also measure the depth of the flaws (Wang et al. 2001). Electromagnetic Microwave Techniques (EMT) EMT uses the special band of electromagnetic wave as the inquiring agency. As an active method, it is based on the physical laws on microwave generation, propagation and reception. By determining the wave velocity, reflection coefficient, and the attenuation and the velocity of the microwave packet to be tested, reliable and reproducible results can be obtained, which also depend on electromagnetic parameters of the material and the geometrical parameters of the object. By measuring the time of flight of microwaves, or the attenuation during passing through the testing object, or the reflection/transmission coefficients, one can deduce the parameters of the tested object, hence, to deduce some information about the structure and the mechanical properties of the tested object. As most of the non-metal materials are transparent to electromagnetic

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18 waves, EMT possesses many advantages over other techniques. It can penetrate more deeply than ultrasound and is very sensitive in detecting the foreign metal objects inside the non-metal matrix, such as steel bars in concrete. It can detect a flat defect, which is difficult to detect by X-ray techniques. It is not sensitive to aggregate size and type. It can precisely locate the objects and has a wide range of measurement from microns of thickness of paint coating to meters of concrete articles. GPR is one of the most successful techniques using in bridge damage detection. It has been used for detecting bridge pier scour and deck delamination (Wang et al. 2001). Optical Techniques (OT) OT uses light waves as the inquiring agency. It is an active method and is based on interferometry and energy transportation. Representative of OT techniques applied in bridge damage detection is Infrared Detection (IRD). IRD uses the infrared light as the inquiring agency. It does not rely on the wave properties as do other wave based techniques. The thereto-properties of materials provide the basis for the measurements. It is also a non-contact, remote, and real time technique. The temperature resolution can reach 0.01 o C. Different kinds of Infrared Thermometer (IRT) systems are used in the implementation of IRD. IRT maps the isotherms over the surface of a component using a heat-sensitive device. By being loaded with heat energy, for example the sun's radiation, the object to be tested is pre-heated. There is a temperature distribution formed and the defects beneath the surface will affect the surface temperature and cause differences in the surrounding area, which can then be recognized from the map. IRT systems have been used for detecting delamination of reinforcement concrete bridges. Yanev (1995), Zachar et al (1992), and Maser et al (1990) have presented the principles and application

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19 of IRT for detecting deterioration of bridge decks. TFHRC (1997) has reported two ongoing projects applying IRT: 1) to detect and quantify the fatigue cracks in steel highway bridges; 2) to develop a dual-band IRT imaging system for bridge deck inspection (Wang et al. 2001). Other Techniques There are also many other NDT&E techniques applied in bridge damage detection. These techniques could be an innovation and/or an integration of the techniques mentioned above. One example is the embedded corrosion microsensor (ECMS). The ECMS is developed to quantitatively measure the corrosion activity inside concrete. It is small and inexpensive which will allow hundreds or thousands of them to be embedded in concrete structures. The integrated circuit provides electrochemical measurements of corrosion rate with polarization resistance, and measures chemical parameters such as pH, chloride ion concentration, and temperature in an embeddable package. It is powered and it telemeters sensor data via wireless communication. Vibration-based damage detection methods have been successful to a certain extent, especially when the overall damage is significant. However, their application in bridge structures is often challenged since significant local damage might not cause observable difference in the observed quantities and because the number of measurements which can be made is limited. Much of this is related to systematic errors between the model and the structure and the non-stationary of the structure, and the modal data of concrete structure is particularly different to interpret, due to the non-uniformity of the material. Robust identification techniques that are able to locate damage based on realistic measure data sets still seem a long way from reality. Certainly however, if the horizons are

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20 reduced and significant prior knowledge of the structure is included and sufficient measurements are taken, some progress can be made in some applications. One scenario is that damage detection using low frequency vibration is undertaken to identify those areas where more detailed local inspection should be concentrated. The most promising methods seem to be based on modal data and rely on the forward type identification methods. Even so, relying on low frequency vibration data will always be able to locate damage with a limited accuracy because of the global nature of the methods. Special instruments have shown great advantages in doing some specialized things better and more effectively than the general one. More commercial instruments for different specific purposes need to be developed. In bridge damage detection a problem usually requires different NDT&E techniques. Two or more independent techniques are needed for confidence in the results. However, information from different NDT systems can be conflicting, incomplete or vague if studied as discrete data. The new data fusion techniques seem to light the way to correct answers (Wang et al. 2001). Split Spectrum Processing SSP was initially introduced to enhance the signal-to-noise ratio for nondestructive testing of materials. This technique was shown to be effective in flaw enhancement, particularly in the detection of targets with similar spectral characteristics, yielding the hidden target information. The SSP method has been successfully used for noise suppression in non destructive testing of stainless steel and has the potential to improve detection of discontinuities in concrete as well. However, application of SSP to concrete is difficult because the internal structure of concrete varies within much wider limits than that of polymer composites or material, and the scatterers in concrete vary in

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21 size to a much greater extend than in metals. There are several different scatterers in concrete, such as aggregate particles, voids, cracks, delaminations, etc. This is a more complex microstructure than in metals; the aggregate type and quantity can vary within can vary within wide limits in concrete. However, the preliminary tests have produced encouraging results with SSP, which appears to be a promising new technique for concrete inspection. In SSP, the backscattered wideband signal from concrete passed through a Gaussian filter bank to obtain signals at different normalized individually, giving zero-mean outputs. This introduces weighing to the frequency bands, which should have the effect of flattening the original spectrum, thus broadening the effective bandwidth and improving the system resolution. Subsequently, these signals are combined nonlinearly to obtain the processed signal where the interference noise caused by backscattering is suppressed. Split spectrum processing makes it possible to use ultrasound of MHz frequencies for testing. Despite the presence of significant scatterer noise, both the minimization and polarity shareholding algorithms reduce the noise level and help identify the ultrasonic signals reflected from the back surface and targets of interests. The experimental results demonstrate the potential of SSP for signal-to-noise enhancement of high-frequency ultrasound signals in concrete. This improvement can be related to the decorrelation of grain echoes resulting from frequency shifts between the transmitted signals. These results not only illustrate the capability of SSP in detecting multiple targets simultaneously, but also the ability of detecting discontinuities that are not readily visible in the unprocessed data. SSP is effective for detection of discontinuities and thickness measurement in concrete. The methods can be easily

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22 extended to two dimensional ultrasonic imaging of concrete, which is planned in future work (Karagouz et al. 1998). Acoustic Tomographic Imaging of Concrete Infrastructure According to Rens et al. (2000), Schuller et al. (1994) used the tomography technique to monitor the effectiveness of grouting repairs to masonry structures (Acoustic Tomographic Imaging of Concrete Infrastructure).Tomograms taken before and after grout injection were compared. The postrepair tomograms showed areas of increased velocity, indicating sound material. Rhazi et al. (1996) report success using a similar method. Several successful efforts have been made to image concrete sections with X-ray and gamma-ray tomographic systems. Morgan et al. (1980) used X-ray scanners to create tomograms of concrete cylinders. Narrow cracks of <1 mm in width were clearly identifiable. Martz et al. (1993) produced images of reinforced concrete specimens with a spatial resolution of 1 mm in the laboratory using a gamma-ray scanner. Where Martz scanned from all angles, Heiskanen et al. (1991) used a gamma-ray tomographic system to image reinforced concrete specimens from a limited number of angles. Olson and Sack (1995) developed an acoustic imaging system for quality assurance testing of drilled pier foundations. Adapting the geophysical technique of cross borehole tomography, boreholes are cast in the foundations and sending and receiving probes are sent down the water-filled holes. Tomographic images are created from this data to check the integrity of the material between the boreholes. Defects have been successfully located in the field with this system (Rens et al. 2000). Jalinoos and Olson (1995) developed a high-speed ultrasonic tomography system to detect flaws in concrete structures with two-sided access, such as bridge members,

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23 columns, and walls. This research effort focused on the development of a rapid data acquisition method in order to make the technique practical for general use. A rolling ultrasonic transducer was used to send signals at regular spatial intervals to an array of fixed receivers on the opposite side of a test wall. This system proved capable of locating flaws that had been cast into the test wall (Rens et al. 2000). Schuller and Atkinson (1995) and Woodham et al. (1996) developed an acoustic tomography system for structural concrete and masonry. This system can locate large steel inclusions, voids, cracks, and zones of low density. This system provided useful results for an evaluation of a masonry structure, where tomographic images were used to identify cracks and deteriorated material in a masonry wall (Rens et al. 2000). The radiographic methods mentioned in the literature review produce excellent tomographic images but require expensive equipment that is not field portable at this time. The images produced using acoustic tomography have less resolution than those of the radiographic methods (-5-20 cm as opposed to 1 mm), but the equipment is more economical and does not require extensive training and safety precautions. The cost of the X-ray and gamma-ray systems is about 10 times that of an acoustic system. The data collection for acoustic tomographic analysis is performed using the same equipment that is commonly used for ultrasonic testing, with the exception of the multiplexing system (Rens et al. 2000). The results of a survey of the state DOTs indicate that such applications are attractive to the practicing NDE community. The lack of standards for the technique is a drawback for routine use, but the procedure is relatively straightforward and could lend itself well to standardization. Colorado, working group sessions were held to help

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24 brainstorm standardization techniques for several different construction materials and NDE techniques. In the official working group report that followed these sessions (Schuller and Woodham 1996), recommendations toward the standardization of tomography were proposed. Copies of the working group report were forwarded to the American Society for Testing Materials. Leiphart et al. (1999) developed a statistical process called a gauge potential study, which improves the reliability of acoustic tomography. This gauge study also holds possibilities for incorporation into a standard. The use of the array halved the time required collecting a data set. Concerns about result interpretation continue to be a problem associated with all non destructive techniques. Unfortunately most NDT results are still user dependent and interpretation can take some degree of ingenuity (Rens et al. 2000). The pulse echo technique is carried out by sending frequency modulated chirp signals and performing a cross correlation between the received and the transmitted signal. In combination with the application of recently available ultrasonic concrete probes as transmitter, this leads to an improvement of the signal to noise ratio. A laser doppler interferometer, equipped with a random speckle modulator, is used as detector of the ultrasound. Finally, the data sets can be processed with various methods, involving the time signals of several space points. The improvement compared to standard laser interferometric measurements will increase the feasibility of laser interferometric detection for non-destructive testing in civil engineering. The difficulties of non destructive testing of concrete by ultrasonic methods result from the strong signal attenuation, caused mainly by scattering at the in homogeneities of concrete. Besides decreasing the transmitted ultrasonic signal, it leads to strong coherent noise. This noise

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25 can mask even large back wall echoes totally. Scattering diminishes for decreasing frequencies. Therefore, rather low frequencies in the range of about 100 kHz must be used. Highly efficient transducers have been developed and are available now. Pulse-compression is known to improve the signal to noise ratio in situations with a high insertion loss. It has been applied to ultrasonic testing of concrete successfully. It is well known from ultrasonic testing in other fields, that space averaging techniques suppress the coherent back-scattering noise effectively (Koehler et al. 1997). For applying such methods, signals from a large number of measurement points are necessary. They can be obtained in a convenient way by using laser interferometric detection. In the interferometric detection is performed in a 2D scanning aperture and the measured data are reconstructed by the 3D-SAFT algorithm involving itself spatial averaging. Till now the main problem of laser interferometry has been the insufficient sensitivity, resulting in a low signal to noise (S/N) ratio. This is a special problem in an automatic scanning mode, because no fine focusing can be performed, resulting in large incoherent (electronic) noise of the interferometer. Thus, improvement of the signal to noise ratio is crucial for application of laser interferometric detection and space averaging techniques. S/N ratio can be improved by several methods. On the one hand we increase the signal by applying the very efficient probes mentioned above as transmitter and including the pulse compression technique in our system and on the other hand we reduce the laser vibrometer noise by implementation a random speckle modulation technique C. By this method we get signals of tolerable incoherent noise appropriate for signal processing to suppress the additional coherent scattering noise.

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26 The first results demonstrate the efficiency of ultrasonic testing with laser interferometric detection. In co-operation with pulse compression and random speckle modulation the signal to noise ratio can be reduced so that laser interferometric detection becomes practicable. The technique has to be developed to increase the processing speed. The described technique may help to improve the acceptance for ultrasonic methods in civil engineering. The 3D-SAFT reconstruction is able to increase the signal to noise ratio further and leads to a 3D-image of reflector distributions inside the specimen. Furthermore, the presented technique can be used as an advanced tool for experimental verification of modeling results concerning the propagation of ultrasonic waves in concrete (Koehler et al. 1997). Impact-echo technique is a method for nondestructive evaluation, detecting elastic waves due to a mechanical impact. Although the impact-echo is reported to be promising for quantitative estimation, applicability to evaluation of post-tensioning tendon ducts is not confirmed yet. To this end, the basic theory of the impact-echo should be clarified. In this case, a specimen containing ungrouted duct is tested. Theoretically, frequency responses of the specimen depend on the size, orientation of the void, and P-wave velocity, while wave motions in concrete structures are characterized by material properties, incident waves, and size of members. Thus, the frequency response is studied from the relationship between the wave length and the depth of duct. Experimentally, impact tests are conducted by dropping steel balls and shooting aluminum bullets. The analysis is carried by the boundary element method (BEM). As a result, the detection of resonance frequency due to the presence of void is clarified, relating with impact frequencies and the depth of duct (Watanabe et al. 1999).

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27 In the Comparison of Pulse-Echo-Methods for Testing Concrete, it has been shown that one of the principal objectives of the development of NDT-CE techniques is a reliable assessment of the integrity or detection of defects of concrete members even when they are accessible only from a single surface. Especially on reinforced concrete structures such inspections could in the past only be solved by means of radiography (for concrete thickness less than 0.6 m) or by using more or less destructive methods. Some of the current research aims are outlined below: (NDTnet 1996): location of tendons detection of voids in tendon ducts detection of compression faults or honeycombing information on geometrical dimensions The used methods are briefly described below: Radar The radar investigation has been performed with the nominal 900 MHz antenna (center frequency: 1 GHz). First the transmission velocity of the electromagnetic waves was determined at different positions of both specimens. From these velocities, average dielectric constants of (8.7 +/0.2) and (9.4 +/0.3) were determined for specimens 1 and 2, respectively. For locating the metallic duct and for thickness determination, the antenna has been moved in parallel tracks over the surface of the specimen. The amplitudes illustrate the strength of the reflections. From the dielectric constant and the transmission time, a concrete thickness of (508 +/10) mm is calculated. The concrete cover on the duct is (340 +/10) mm. The lateral position of the duct can be determined

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28 with an accuracy of +/10 mm. The measurement results of both types of specimens with different Aggregate size do not differ significantly. Because of electromagnetic shielding the Radar measurements are not suitable to detect voids in the metallic ducts (NDTnet 1996). Impact-Echo The impact-echo testing was performed using an impactor with a spring driven mass and piezo-electric displacement transducer, the frequency analysis was affected using a laptop. The multiple reflections of the longitudinal waves are analyzed to locate the duct and to measure the thickness. This gives clear peaks when only back wall reflections are apparent. When the duct position is measured from the near surface, the maximum corresponding to the position of voids in the duct (17.3 kHz) is clearly detectable together with the back wall echo at 3.9 kHz. The impact response from the filled duct. The frequency of the reflections from the duct is characterized by multiple peaks with lower amplitude (interface section) and differs from the signals from an unfilled duct. The result shows that it is feasible to use the impact-echo method to detect the ducts, but has to be improved by field studies (NDTnet 1996). Ultrasonic Pulse Echo, A-scan In order to overcome the specific problems of concrete, a specially developed low frequency flaw detector for construction site testing of strongly attenuating (sound scattering) materials was applied in combination with low frequency probes especially optimized for this field of application. Its A-scan display enables, even with concrete, the evaluation of the signal amplitudes and times of flight as with common ultrasonic

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29 material testing. Most of the test tasks set here could be solved for the specimen 1 (8 mm maximum Aggregate size) with satisfactory results (NDTnet 1996). Ultrasonic Pulse Array The tests were performed with an array consisting of seven transducers. The fast setting mortar used as coupling agent is well matched to the acoustic properties of concrete. Another advantage is that the transducer array is held in the desired position without any additional device. The equipment used is described in detail in these proceedings. Measurements were made at all transmitter/receiver-combination of adjacent transducers. This means a total of 24 single shots which cover an area of approximately 150 mm in diameter. The signals are processed by spatial averaging to suppress the effects of scattering at Aggregate particles. Signal processing was done by matched filtering and calculation of the envelope by utilizing the complex analytic signal. An explanation for the slight deviation of the depth measurement is the fact that the array covers an area so that the geometrical situations are not exactly the same for all single measurements (NDTnet 1996). Ultrasonic Pulse Echo, B-scan By manually moving the US-IE transducer along the concrete surface (specimen 1, surface A) B-scans were generated on-line. This permits a lateral localization of the duct within 5mm. This was repeated along 16 axes of the surface, so that the localization of the duct could be measured precisely. The position in the depth was interpreted from the simultaneous measured A-scans in the range from 102 to 78 mm depending on the site. The measurements were also possible from the reinforced half of

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30 the specimen, but yet no difference between void and filled duct could be detected. Further details are described (NDTnet 1996). Ultrasonic Pulse Echo, B-scan, LSAFT Ultrasonic data is recorded in single transducer pulse echo technique along a linear aperture at regular spacing. A SAFT-imaging algorithm is employed to reconstruct a 2-dimensional section of the material below the aperture. The resulting images, usually B-scans and demodulated SAFT-images, are plotted by means of the analysis software (NDTnet 1996). Aggregate size, sound path, and transducers contact to surface are most important to influence the quality of the images. The accuracy of the localization of an object depends on the knowledge of the exact pulse velocity which in turn depends on the length of the transit path due to dispersion (NDTnet 1996). Ultrasonic Pulse Echo: 2D-Synthetic Aperture and 3D-SAFT When the two dimensional synthetic aperture technique is utilized with separate transmitter and receiver probes, the echoes from different directions will overlay. The negative influence of statistical materials in homogeneities can better be minimized than with a linear aperture. Additionally the measurement accuracy will be improved when shading appears. When the method of phase corrected superposition is applied (algorithm for thickness measurement on the basis of 100 A-scans), the thickness of a specimen without and with mesh reinforcement can be very accurately determined (NDTnet, 1996). A large number of data is required for applying the 3D-SAFT algorithms. They are produced in our investigations by using a scanning laser Doppler vibrometer as an ultrasonic detector (typical number of dots 1000, screen width 10 mm). Another

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31 advantage of this technique is that apart from applying a reflective coating no special preparations are required even for very rough surfaces. The diameter of the void is about 20% of the aperture diameter so that the void and the tendon duct can easily be identified when the thickness-sensitive algorithm is applied (NDTnet 1996). The three-dimensional image is produced according to the principle of the three-dimensional SAFT reconstruction. The intensity maximum correlates with the void position and indicates. No signals are received from the filled tendon duct so that the unfilled area can easily be identified (NDTnet 1996). EFIT Simulation The Elastodynamic Finite Integration Technique (EFIT) is an efficient numerical code to model the propagation and scattering of elastic waves in inhomogeneous solids. For applications to concrete a special two-dimensional version has been developed, which allows to model statistical in homogeneities in terms of arbitrarily oriented ellipses of random distributed sizes and material properties. The code produces time frames of spatially propagating wave fronts and time histories of received signals on the specimen surface, so-called A-scans, A set of Ascans along a one-dimensional scan line can be post processed either with the conventional SAFT-algorithm or with a more elaborated EL-FT-SAFT scheme, which accounts for the elastodynamic nature of ultrasound and which includes mode conversion between pressure and shear waves (NDTnet 1996). The post-tensioning system of the Mid-Bay Bridge has undergone a rigorous and testing regiment since the discovery of failed external post-tensioning tendons. FDOT and consultant inspection personnel have worked systematically and aggressively to catalog the condition of the bridge’s post-tensioning system. The major inspections and tests

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32 conducted were (FDOT 2001): Sounding Post-Tensioning Tendons for Voids Bore Scope Inspections of Post-Tensioning Anchors Vibrating Testing Visual Void Inspections Mag-Flux Testing Grouting Mock-Up Tests Other Corrosion Related Testing No one inspection or testing procedure is able to provide a complete evaluation of the corrosion of external post-tensioning tendons. Tests that give good results in the free length of external tendons do not give any results in the anchorage zones. Tests that give strong indications of active corrosion in a length of tendon do not necessarily predict the level of force in the tendon or section loss that has occurred. The proper approach for inspecting external post-tensioning tendons is to conduct a battery of tests specifically chosen to develop an understanding of the tendon conditions. This was effectively accomplished for the Mid-Bay-Bridge (FDOT 2001). Table 1-1. Summary of NDT Techniques * Material Detection Technique Plain Concrete Reinforced Concrete Post-tensioned Concrete Steel Void Crack Corrosion Ducts Ultrasonic Tomography Theory (Martin et al. 2001) X X X Reflection Seismology (Chang et al. 2001) X X Spectral Analysis or Ultrasonic Signal (Halabe & Franklin 1999) X X

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33 Table 1-1. Continued Material Detection Technique Plain Concrete Reinforced Concrete Post-tensioned Concrete Steel Void Crack Corrosion Ducts Ultrasonic Testing (Yieh & Huang 1998) X X X Traditional Piezoelectric EXcitation (Popovics et al. 1999) X X Mechanical Wave Techniques (MWT) (Wang et al. 2001) X X X Electromagnetic Microwave Techniques (EMT) (Wang et al. 2001) X X X Optical Techniques (OT) (Wang et al. 2001) X X X X X Split Spectrum Processing (Karagouz et al. 1998) X X X X Acoustic Tomographic Imaging of Concrete Infrastructure (Rens et al. 2000) X X X Radar (NDEnet 1996) X X X X X Impact-Echo (NDEnet 1996) X X Ultrasonic Pulse Echo, A-scan (NDEnet 1996) X X EFIT Simulation (NDEnet 1996) X X * * The techniques presented were used by the authors for dectecting the type of material flaw(s) listed. This does not limit them from being applied to detecting other types of material flaws.

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CHAPTER 3 SURVEY OF STATE DEPARTMENTS OF TRANSPORTATION Introduction A survey of Department of Transportation (DOT) was performed to determine their policies toward the use of post-tensioning concrete beams, and to collect information on any guideline on this subject. The survey was distributed to the Department of Transportation’s Material Engineers for each state including Puerto Rico (52 total); of the 52 departments contacted, 33 responded, (63% response rate). A copy of the survey is shown in Appendix A. Results of the Survey The raw data representing the results of the survey is shown in Appendix B. Of the 33 state agencies that responded to the survey, 20 states indicated that they use bonded post-tensioning systems, 3 states use unbonded post-tensioning systems, and 10 did not reply to the question. Figure 3-1 presents the number of states that use different systems of post-tensioning. 34

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35 3 20 05101520Number of Use UnbondedBondedBonded v.s. Unbonded Posy-tensioning Systems Figure 3-1. Results of Post-Tensioning Systems (Bonded and Unbonded) Figure 3-2 represents the duct material that is used by the responsive DOTs. They were classified into two categories, plastic or metal. 13 20 05101520Number of Use PlasticMetalDuct Material Use Figure 3-2. Frequency of Duct Material Used in Post-Tensioning

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36 Figure 3-3. includes the different classes of grout used in post-tensioning. Actually they are four classes: A, B, C, D, and others. 4 4 2 12 024681012Responses ABCDClassesBonded Grout Class Figure 3-3. Bonded Grout Class Used. The proportions of grout ingredients in Classes A, B, and C shall meet the requirements given in Table 3-1. The grout properties for class D grouts shall be specified by the Design Engineer to suit the special application.

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37 Table 3-1. Range of Material Quantities for Class A, B, C, and D. Constituent Materials Cement Fly Ash Fly Ash Slag Silica Water/ High Range Calcium (kg) (Class F) (Class C) % Fume Cementitious Water Nitrite % % (dry) Material Ratio Reducer (kg/m3) Class Exposure % (Type F or G) NonAggressive: Indoor or nonAggressive: A outdoor 100 0 0 0 0 Max.0.45 0 0 Aggressive: Subject to wet/dry cycles, marine environment, B deicing salts 100 Min. 0 Max. 25 Min. 0 Max. 30 Min. 0 Max. 55 Min. 0 Max. 15 Max.0.45 Min. 0 Max. 3 liter Min. 0 Max. 30 NonAggressive or C Packaged Aggressive Max.0.45 D Special Determined by Design Engineer Tables 3-2 and 3-3 describe the nondestructive inspection method and the failure experienced by the reporting DOTs for the bonded post-tensioning systems respectively. The results showed that none of the responsive DOTs use nondestructive testing or have even experienced any failure in their bonded post tensioning systems. Table 3-2. Nondestructive Inspection Method. Non destructive Inspection Response No 23 Yes 0

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38 Table 3-3. Post-tensioning Failures Experienced by DOTs Tendon's Failure Response No 22 Yes 0

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CHAPTER 4 RESEARCH METHODOLOGY Introduction Figure 4-1 provides a graphic of the methodology followed for this research. The first step was to generate a literature review of past studies involving testing post-tensioned concrete elements and ducts. A survey was generated and distributed to all state departments of transportation to establish a possible idea about the use of post-tensioning, ducts, failures and the availability of testing procedures for post-tensioned concrete members. The results of this survey were analyzed using a standard statistical analysis. After that, a concrete sample including plastic and metal ducts was cast in the Rinker School of soils laboratory for the experimental purpose of testing it using the various testing techniques. Literature Review Statistical Analysis Survey Results, conclusions, & recommendations Casting Concrete Testing Sam p les Analyzing Data Figure 4-1. Research Methodology Flow Chart 39

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40 NDT Technologies to be Evaluated Ground Penetrating Radar (GPR) Ground Penetrating Radar was not incorporated in this test series due to the fact that it is primarily used in this application to locate the position of the ducts incorporated in hardened concrete, since this was not a problem with this test series, this test was not performed. Impact Echo (IE) Impact Echo has been used successfully since the end of 1980s to detect cracks or voids in concrete slab or beam, and has also been used to detect defects inside of bonded post-tensioned ducts where the ducts are metal. Impact Echo requires only one-side access to the sample and incorporates Olson’s new technology of “scanning” impact echo measurements, whereby a data point is taken every 0.8-inches of travel. This improvement allowed for faster testing and also improved the accuracy of the testing. This test was run on our samples, but difficulty was experienced in maneuvering on the small beam sample sizes, as shown in Figures 5-1 and 5-2. Ultrasonic Pulse Velocity Tomography (UPVT) The Ultrasonic Pulse Velocity Tomography test requires access on 2 sides of a structural element in order to send and receive sound waves at multiple angles above and below ducts that allows imaging of internal concrete and duct conditions. The current technology uses a single source and single receiver which results in a slow field testing process. This test was run on the four samples described previously. Olson is in the process of producing a scanning UT device that may be evaluated during the next round of tests, instead of using a single source and single receiver, an array of sources and

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41 receivers will be used. This improvement will tremendously speed up the testing process, Figures 5-7 and 5-8. Spectral Analysis of Surface Waves (SASW) The SASW method requires only one side access to the structure. In general, the SASW method uses the dispersive characteristics of surface waves to determine the variation of the shear wave velocity (stiffness) of layered system with depth. The SASW test was also performed on the test samples with great difficulty due to the beam sample size. Data was not obtainable using this technique due to the beam sample size. Olson Engineering, Wheat Ridge, Colorado, was identified as an organization that appears to have the necessary technology, know-how and experience to actively take part in this investigation. Olson have agreed in principle to provide the necessary equipment, on a rental basis, and the technical training to operate the equipment to evaluate a variety of NDT techniques on various grouted duct samples. The testing consisted of three phases: Phase I. In Phase I of this study, small beam samples (4-in x 4-in x 21-in) and (6-in x 6-in x 21-in) were prepared, incorporating small diameter corrugated metal and plastic ducts, 2-inches in diameter, and 3-inches in diameter respectively, and prefabricated defects. Three types of testing were conducted on these samples that included Impact Echo, Spectral Analysis of Surface Waves, and Ultrasonic Pulse Velocity. Phase II. In Phase II of this study, Olson Engineering tested one of the concrete samples (4-ft high x 3-ft wide x 9-in. thick) which were already prepared to have an empty section, partially grouted section, and a completely grouted section. Those sections

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42 were performed in two types of ducts: Plastic and Metal ducts. Three types of testing were conducted on both ducts: Impact Echo, Spectral Analysis of Surface Waves, and Ultrasonic Pulse Velocity. Phase III. In Phase III, the second concrete sample was tested according to the age of grout. Sample size is identical to Phase II. Two tests were done daily during the first week of grout, and one testing was done daily during the following two weeks. Finally, comparisons of the results were made, and conclusions and recommendations were presented. Materials Grout MASTERFLOW 1205, ChemRex Commercial Products Division, was used for grout in the ducts. It is specially formulated to produce a pumpable, nonbleeding, high strength fluid product with extended working time for grouting. It provides corrosion protection for highly stressed steel cables, anchorage and rods. To increase corrosion protection, MASTERFLOW 1205 is formulated with a specially graded aggregate that mitigates chloride migration while still allowing the product to be easily pumped long distance through small openings. The technical data guide and the material safety data sheet (MSDS) can be found in Appendices C and D respectively. Mixing Grout Since higher shear mixing improves fluidity, a drill with a 950 to 2900 rpm was used. Two gallons of water were added to every cement bag to achieve the necessary placement consistency. Three minutes of mixing with 80% of the required water is recommended for the product to reach a uniform consistency. After adding the remaining

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43 water, two additional minutes are required for mixing. Ducts Two types of ducts were used in this study. Corrugated metal and corrugated plastic of 3inches and 2-inches in diameter respectively (Phase I), and corrugated metal and corrugated plastic both of 3-inch ID during Phase II and III. Tendons For the purpose of the study, #6 and #8, 1-inch diameter Grade 60 bars (Phase I) and #3, 3/8-inch Grade 60 bars for (Phase II and III) were used instead of tendons which should not make any difference in the testing or analysis of results.

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CHAPTER 5 TEST RESULTS AND DISCUSSION Introduction A company was identified, Olson Engineering, Wheat Ridge, Colorado, that has the necessary technology, know-how and experience to actively take part in this investigation. They agreed in principle to provide the necessary equipment, on a rental basis, and the technical training to operate the equipment to evaluate a variety of NDT techniques on various grouted duct samples. PHASE I 1. Two6”x6”x21” concrete beam samples were prepared incorporating a 3-inch diameter corrugated steel duct. A #8 steel reinforcing bar was centered in the duct and defects were introduced into both samples prior to grouting the bar in-place. (See Figures 5-1, 5-2, and 5-3). 2. 24x4x21-inch concrete beam samples were prepared incorporating a 2-inch diameter plastic duct. A #6 steel reinforcing bar was centered in the duct and defects were introduced into both samples prior to grouting the bar in-place. (See Figures 5-1 and 5-4). 3. Grout used for the samples was Masterflow 1205, an FDOT approved post-tensioning grout produced by ChemRex Commercial Products Division. 4. The samples were allowed to water cure for 14 days prior to testing 5. A representative from Olson Engineering performed the testing and training of lab personnel. Tests performed included “scanning” Impact Echo, static Ultrasonic Pulse Velocity Tomography (UPVT) and Spectral Analysis of Surface Waves (SASW). 44

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45 Figure 5-1. Grouted Beam Samples Figure 5-2. Grout Beam Samples with Defect Locations Schematic representations of the defect locations for both the grouted 3-inch corrugated metal duct samples and the grouted 2-inch plastic duct samples are shown in Figures 5-3 and 5-4.

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46 Figure 5-3. Schematic of Defect Type and Location for Grouted 3-inch Corrugated Metal Duct Samples. Figure 5-4. Schematic of Defect Type and Location for Grouted 2-inch Corrugated Plastic Duct Samples.

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47 NDT Technologies Evaluated Impact Echo (IE) Impact Echo requires only one-side access to the sample and incorporated Olson’s new technology of “scanning” impact echo measurements, whereby a data point is taken every 0.8-inches of travel. This improvement allowed for faster testing and also improved the accuracy of the testing. This test was run on our samples, but experienced difficulty maneuvering on the small beam sample sizes. Spectral Analysis of Surface Waves (SASW) The SASW method requires only one side access to the structure. The SASW test was also performed on the test samples with great difficulty due to the beam sample size. Data was not obtainable using this technique due to beam sample size. Ultrasonic Pulse Velocity Tomography (UPVT) The UPVT test was performed to 2 sides on a structural element. The current technology uses a single source and a single receiver which results in a slow field testing process. This test was run on the four samples described previously. Figures 5-5 and 5-6 show the IE scanning devise that was used on our samples; however it is obvious that the IE scanning devise could barely run on the samples due to the small sample size. Figures 5-7 and 5-8 show the UPVT test that was used on the samples. Sample size was not a problem for this kind of testing, the samples were easily accessed from both sides, and conductive grease was used for conductivity between the concrete surface and the transducers.

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48 Figure 5-5. Scanning IE Device and Data recorder Figure 5-6. Close-up of Scanning IE Device Relative to Specimen Size

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49 Figure 5-7. Static Ultrasonic Pulse Velocity Tomography (UPVT) Test Figure 5-8. UPVT Test in Progress

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50 Phase I Results Initially, beams were produced using both 3-inch corrugated metal ducts and 2-inch plastic ducts. The ratio of duct area to concrete area (/16) was kept constant as well as the steel area to duct area ratios (1/9). The problem was that equipment Olson Engineering produced was designed to scan transverse to the duct rather than along the duct longitudinally. Therefore, larger test specimens that would allow for transverse inspection should be used. Transverse detection should not pose a problem for prestressed or posttensioned double tee beams, inverted tee beams, hollow core slabs, AASHTO I-beams, or AASHTO box beams. PHASE II Two mockup walls, each with one plastic duct (3-inch ID) and one steel duct (3-inch ID), were used in this investigation. The post-tensioning ducts on the first wall (Wall I) were divided into 3 sections. The bottom section of both ducts was fully grouted, the middle section of the ducts was partially grouted and the top section was left empty. Both ducts were filled with grout at the very top of the ducts. The second wall (Wall II) had both steel and plastic ducts inside without any grout, i.e. ungrouted void duct conditions. Both types of walls are shown in Figure 5-10 with wall I located to the right and wall II to the left. The walls are 9.0 inches thick, 3 ft wide and 4 ft high. A 3-D schematic picture including the internal grout conditions and the wall sample dimensions is shown in figure 5-9. The ducts location and spacing are also shown in the picture.

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51 Figure 5-9. Reinforced Concrete Dimensions and Duct Location Steel Duct Plastic Duct Figure 5-10. Two Concrete Walls with Steel and Plastic Ducts

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52 Background Three nondestructive test methods were used to evaluate the internal grout condition of steel and plastic ducts. The methods used in this investigation were Impact Echo (IE) Scanning, Tomography with Ultrasonic Pulse Velocity Tomography (UPVT) and Spectral Analysis of Surface Waves (SASW). Detailed analysis of the three methods is presented herein. Impact Echo (IE) Method The IE tests performed in this investigation involved impacting the concrete wall with a small solenoid operated impactor and identifying the reflected wave energy with a displacement transducer. Initially, an Olson Instrument IE-1 handheld unit was pressed against the concrete slab as shown in Figure 5-11. The resonant echoes of the displacement responses are usually not apparent in the time domain, but are more easily identified in the frequency domain. Consequently, the linear frequency spectra of the displacement responses are calculated by performing a Fast Fourier transform (FFT) analysis to determine the resonant echo peak(s). The relationship among the resonant echo depth frequency peak (f), the compressional wave velocity (V P ) and the echo depth (D) is expressed in the following equation: D = V p /(2*f) (1) where is a factor equal to 0.96 for a slab/wall shape Figure 5-11 illustrates the reflection of the wave upon hitting a void in the concrete or upon reaching the edge of the concrete element. The receiver catches the reflected wave and its characteristics will be saved in a connected data PC system to be examined.

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53 FOlson Instruments, Inc. Impact Echo IE-1test head incorporating source and receiver*Reflection from backside occurs at a lower frequency than thatfrom the shallower concrete/flaw interfaceReflection from concrete/flawinterfaceReflection from backside oftest member* Receiver Source law Void Figure 5-11. Schematic of Impact Echo Method The IE method can be used for measuring concrete thickness, evaluating concrete quality, and detecting hidden flaws such as cracks, honeycombs, etc. The IE test data was recorded on an Olson Instruments Freedom Data PC during the laboratory NDT. To expedite the IE testing process, Olson Instruments has developed and patented an Impact Echo Scanning device with four wheels and a rolling displacement transducer with 6 sensor elements attached underneath the test unit. As the test unit was rolled along the concrete surface, the central transducer wheel kept track of the distance. The IE scanner unit is designed to apply an impact every 0.8 inch.

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54 IE Scanner Unit Olson InstrumentsData Freedom PC Figure 5-12. Freedom Data PC Acquisition System with IE Scanner Figure 5-13. The Impact Echo Scanning test The Freedom Data PC acquisition system and an Impact Echo Scanning unit are shown in Figure 5-12. The Impact Echo Scanning test is shown in Figure 5-13. Spectral Analysis of Surface Waves (SASW) Method The SASW method uses the dispersive characteristics of surface waves to determine the variation of the surface wave velocity (stiffness) of layered systems with

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55 depth. The SASW testing is applied from the surface which makes the method nondestructive and nonintrusive. Shear wave velocity profiles can be determined from the experimental dispersion curves (surface wave velocity versus wavelength) obtained from SASW measurements through a process called forward modeling (an iterative inversion process to match experimental and theoretical results). The SASW method can be performed on any material provided an accessible surface is available for receiver mounting and impacting. Materials that can be tested with the SASW method include concrete, asphalt, soil, rock, masonry, and wood. Applications of the SASW method include, but are not limited to: 1) determination of pavement system profiles including the surface layer, base and subgrade materials, 2) determination of seismic velocity profiles needed for dynamic loading analysis, 3) determination of abutment depths of bridges, and 4) condition assessments of concrete liners in tunnels, and other structural concrete conditions. The SASW method requires an accessible surface for receiver attachments. The extent of the accessible surface limits the investigation depth. As a rule of thumb, if one is interested in material properties to a depth of D, then the accessible surface should extend in a line of receivers direction to a distance equal to 1.5D, preferably 2D. Figures 5-14 and 5-16 show the general field arrangement used in SASW testing. Receiver spacings ranging from 0.25 to +300 ft have been used in the field by Olson’s to investigate depths from 0.1 ft up to +300 ft.

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56 Receiver R1Receiver R2 d > d/2Source Olson InstrumentsFreedom NDT PC. Figure 5-14. Field Setup for SASW Test Figure 5-15. SASW Test on the Wall In this case, the SASW method was used to check for possible voids inside the ducts. The SASW method uses the dispersive characteristics of surface waves to evaluate concrete integrity with increasing wavelengths (depths). High frequency or short wavelength waves penetrate through shallow depths, and low frequency or long wavelength waves penetrate through deeper depths. If voids exist in the ducts, longer wavelength waves will not be able to propagate directly through this zone and will show a decrease in velocity at duct wavelengths (depths).

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57 Elastic Stress Wave Relationships The following equations from elastic theory illustrate the relationships between shear moduli (G), mass density (, total unit weight divided by gravitational acceleration), shear wave velocity (Vs), Young's modulus of elasticity (E), Poisson's ratio (), compression wave velocity (Vp), and constrained modulus (M): Direct Por SWave Velocity: Vp = D / tp or Vs = D/ts (1) Shear Modulus: G = Vs 2 (2) Young's Modulus: E = 2 (1+ ) Vs 2 = Vp 2 [(1+ )(1-2 )/(1)] (3) Constrained Modulus: M = Vp 2 (4) Poisson's Ratio: = [0.5 (Vp/Vs) 2 -1]/[(Vp/Vs) 2 1] (5) Pand S-wave Velocities: Vp = Vs [2(1)/(1-2 )] 0.5 (6) (Where D = Distance, tp = P-wave travel time and ts = S-wave travel time). Values of these parameters determined from seismic measurements (SASW measurements) represent the material behavior at small shearing strains, i.e. strains less than 0.001 percent. Thus, moduli calculated from compression, shear or surface wave velocities represent the maximum moduli of materials because of their low strain levels. It should be noted that the measurement of the surface wave velocity, also called Rayleigh wave velocity, is actually performed in the SASW test. Surface wave velocity (V R ) in a homogeneous half-space is related to shear wave velocity by: V R ~ 0.9 Vs (7) Surface wave velocity varies with frequency in a layered system with differing velocities. This variation in velocity with frequency is termed dispersion. A plot of surface wave velocity versus wavelength is called a dispersion curve.

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58 The SASW tests and analyses are generally performed in three phases: (1) collection of data in situ; (2) construction of an experimental dispersion curve from the field data; and (3) inversion (forward modeling) of the theoretical dispersion curve, so that a shear wave velocity versus depth profile can be constructed. Wavelength (), frequency (f), and wave velocity (Vr), are related as follows: Vr = f* (8) When the velocity is uniform, the wavelength of the waves is the investigation depth. Forward modeling is used to determine layer thicknesses and velocities when dispersive conditions exist. Forward modeling is most commonly done to determine seismic velocity profiles of soil and rock for earthquake and vibration machine foundation design purposes. SASW Experimental Dispersion Curve Processing The experimental dispersion curve is developed from the field phase data from a given site by knowing the phase () at a given frequency (f) and then calculating the travel time (t) between receivers of that frequency/wavelength by: t = / 360*f (9) Surface wave velocity (Vr) is obtained by dividing the receiver spacing (X) by the travel time at a frequency: Vr = X / t (10) The wavelength () is related to the surface wave velocity and frequency as shown in equation 8. By repeating the above procedure for any given frequency, the surface wave velocity corresponding to a given wavelength is evaluated, and the dispersion curve is determined. The phase data was viewed on the PC data acquisition

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59 system in the lab to ensure that acceptable data was being collected. The phase data was then sent to Olson’s Engineering for processing. Olson used the TFS-SASW software to generate the experimental field dispersion curves presented on this survey. Ultasonic Pulse Velocity Tomographic Imaging (UPVT) with Ultrasonic Pulse Velocity Ultrasonic Pulse Velocity Tomographic Imaging (UPVT) is an imaging method analogous to a CAT-Scan in the medical industry and uses acoustic waves. The testing is often performed on drilled shaft foundations after crosshole sonic testing to obtain more information about the size, shape, location, and severity of a suspected defect or defects in a concrete drilled shaft. This foundation method is known as Crosshole Tomography (CT). A UPVT imagining data collection is intense and the procedure is relatively slow. The spatial resolution of Tomography can be high and an actual image of the specimen is produced. A description of the Tomography test method is given below. In this case the Tomography tests used two ultrasonic transducers (54 KHz), one as a source and the other as a receiver. For Tomography testing, acoustic data are collected for many receiver and source combinations at different depths (Figure5-16). For a typical Tomography data set, sound velocity ray paths are generated for tens to thousands of source-receiver location combinations. The term “ray coverage” describes the area through which acoustic wave rays travel from the many source-receiver position combinations.

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60 SourceReceiver SourceReceiver Figure 5-16. Tomography Test Source and Receiver Combinations at Different Depths Tomography is an analytical technique which uses an inversion procedure on the first arrival time data of compressional or shear wave energy that can produce ultrasonic pulse-velocity based images of a 2-D or 3-D concrete zone inside a foundation or of the entire foundation. This type of tomography is termed “velocity tomography” and can be used together with amplitude tomography. The test region is first discretized into many cells with assumed slowness values (inverse of velocity) and then the arrival times along the test paths are calculated. The calculated times are compared to the measured travel times and the errors are redistributed along the individual cells using mathematical models. This process is continued until the measured travel times match the assumed travel times within an assumed tolerance. The end result is a 2-D or 3-D velocity image (or contour) of the internal structure of the foundation, revealing sound (fast) versus defective (slow) areas. Phase II Results This section describes results from all three NDT methods on both mock up walls in the soils laboratory using the Olson equipment, and the data was processed by Olson Engineering, Inc. (Olson 2002).

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61 Impact echo scanning on wall II (ungrouted ducts) First, an Impact Echo scan was performed on the solid concrete wall between the ducts where no internal post-tensioned duct was present to allow calibration of the IE velocity of concrete Wall II. The thickness results of the first scan, typical frequency response from the concrete wall are shown in Figure 5-17. From the calibration, an IE velocity of 11,000 ft/sec (included 0.96factor per Eq (1)) was used in the Impact Echo test. The average wall thickness from Figure 5-17 is 9.5 inches. The top inset window shows the time domain displacement transducer response at 1 ft from the top of the wall. 7330 Hz Figure 5-17. Nominal Wall Thickness and its IE frequency response from IE Scanning of Solid Concrete The bottom inset window shows the linear frequency spectra of the time domain response at 1 ft from the top of the wall. The thickness echo peak is at 7,330 Hz, so by

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62 applying Eq. (1), the echo depth is: D = V IE /(2*f) = 11,000/ (2*7,330) = 0.75 ft = 9 inches. 5920 Hz Figure 5-18. IE Thickness Results and Example Frequency Response from the Empty Steel Duct of Wall II (Duct Center Line Scan) Two Impact Echo scan lines were performed on Wall II along the center lines of empty steel and plastic ducts. The IE thickness results from the empty steel duct are shown in Figure 5-18. An average thickness from the empty steel duct (Wall I) was 11.3 inches. Typical frequency response from the data is also shown in the inset in Figure 5-18. The thickness frequency peak shifted from 7,333 Hz (Figure 5-17) to 5920 Hz. This shift in

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63 the frequency resulted in a larger thickness response of 11.3 inches due to the decreased resonance as a result of the void of the empty steel duct. The IE results from the empty plastic duct and a typical frequency response are shown in Figure 5-19. The resonant frequency peak of this data is 5,250 Hz which is slightly lower than the peak response from the empty steel duct (Figure 5-18). Correspondingly, the IE peak results predicted an even greater average thickness of 12.5 inches for the larger diameter (bigger void) empty plastic duct than the 3 inch steel duct. 5250 Hz Figure 5-19. IE Thickness Results and Example IE frequency response from the Empty Plastic Duct of Wall II (Duct Centerline Scan) Impact echo scanning on wall I scanning of grouted to ungrouted ducts scanning along the ducts After obtaining the base line data for the ungrouted ducts of Wall II, several IE scanning tests were performed on Wall I. In this case, the scan started from near wall bottom (depth of 0 ft). As described in Section 4.0, both ducts in Wall I were divided into 3 sections: the bottom sections with fully grouted ducts, the middle sections with

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64 partially grouted ducts and the top sections with empty ducts, plus grouted cap at the very top. The first IE scan was performed along the center line of the steel duct, starting from near the bottom (3" above the wall bottom) to near the top (~3" below the top wall) of the wall. The IE thickness results and example frequency responses are shown in Figure 5-20, which shows that the peak frequency shifted to a lower value for the partially grouted and empty steel duct. This resulted in larger apparent thickness results from the partially grouted and empty ducts. An average thickness result from a fully grouted duct section is 9.8 inches and an average thickness result from partially grouted to empty ducts is 10.8 inches. In this case, the results from partially filled duct are similar to the results from the empty duct. This is because the grout was inserted into the duct after hardening to simulate a partially grouted duct situation. Consequently, debonding occurred between the duct and the hardened grout and the IE signal was not able to travel through the debonding. Therefore, the results from both cases (empty duct and partially grouted duct) are similar since the partially grouted duct behaves just as an empty duct in IE tests due to debonding. Review of the IE spectra in the inset figures of Figure 5-20 shows the resonant echo peaks corresponding to empty to partial to grouted duct results that support this. The impactechogram, which shows amplitude intensity of frequency data of the IE test result from the steel duct, is presented in Figure 5-21. The plot presents a shift of frequency to a lower frequency (compared to a fully grouted duct to an empty duct).

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65 6500 Hz5833 Hz Fully Grouted DuctEmpty DuctCap with grout Partially Grouted Duct 5833 Hz Figure 5-20. IE Thickness and Frequency Results from a Steel Duct – Wall I

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66 Figure 5-21. Impactechogram of the IE test Results along the Steel Duct An Impact Echo scan was then performed along the centerline of the plastic duct. The IE thickness and example frequency results are shown in Figure 5-22. An average thickness reading from a fully grouted plastic duct is 10.6 inches with an average peak frequency of 5916 Hz. An average thickness of a partially filled plastic duct is 11.4 inches with an average peak frequency of 5416 Hz. For an empty plastic duct, an average thickness is 11.2 inch with an average peak frequency of 5583 Hz. An impactechogram of the IE frequency data from the plastic duct is presented in Figure 5-25. It is noted that for the fully grouted plastic duct section (the top section),

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67 both lower frequency peak (~ 5,400 Hz) and a higher frequency peak (~5,900 Hz) appears in the impactechogram plot. This lower frequency peak corresponds to lower stiffness from plastic ducts inside the wall. However, the higher peak frequency can still be used to indicate that the plastic duct in the top section is fully grouted. 5916 Hz 5416 Hz 5583Hz FullyGrouted DuctEmpty DuctCap with grout Partially Grouted Duct Figure 5-22. IE Thickness and Example Frequency Results from a Plastic Duct

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68 Tables 5-1 and 5-2 show the results of variation of depth of the wall with the type of duct and its corresponding void. This is done by getting the thickness echo peak frequency in Hertz of each section of the wall from the output of scanning IE, and then applying Eq. (1), the echo depth is: D = V IE /(2*f), where V IE is kept constant at 11,000ft/s. Table 5-1. IE Depth Results for Empty Ducts and Solid Concrete. Solid Concrete Empty Steel Empty Plastic Peak Frequency, Hz 7,330 5,920 5,250 Depth, in. 9 11.1 12.6 Table 5-2. IE Depth Results for Fully Grouted, Partially Grouted and Empty Ducts. Fully Grouted Partially Grouted Empty Duct Material Plastic Steel Plastic Steel Plastic Steel Peak Frequency, Hz 5,916 6,500 5,416 5,833 5,583 5,833 Depth, in. 11.2 10.2 12.2 11.3 11.8 11.3 An explanation of the differences in the wall thickness for each type of void is explained in figures 5-23 and 5-24. Note that the red lines designate the waves emitted by the IE pulse; the green color represents concrete, where the black lines represent the surface of the ducts. For the fully grouted ducts, the wave passes straight through, and the echo depth should be approximately the same as the thickness of concrete. For the empty duct, the echo depth should be t-d+r/2 which is slightly greater than the diameter of the duct.

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69 Where t is the thickness of the wall D is the diameter of the duct R is the radius of the duct. For the partially grouted duct, the problem that is created is the orientation of the void. If the void is on the top as shown in figure 5-23 or if the void is oriented as shown in figure 5-24, the results of each depth will vary due to multiple reflections. Although partially grouted will appear based on scanning IE to be more like the empty duct, than the fully grouted duct. Fully Grouted Empty Partially Grouted Figure 5-23. Schematic of compression wave penetration through the ducts.

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70 Figure 5-24. Schematic of compression wave penetration through partially grouted ducts. High frequency corresponding to fully grouted section Lower frequency corresponding to voids inside the duct Figure 5-25. Impactechogram of Frequency Data from a Plastic Duct

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71 Results from IE scanning when the scanning is off the center line Wall I This section describes the test setup and results when IE scanning was performed off the centerline of the duct. The first scan was performed along the centerline of the steel duct (see Figure 5-16), The second, third and fourth scans were performed 1, 2 and 3 inches off the centerline of the steel duct. The thickness results from all four scans are presented in Figure 5-26. It is interesting to see that the first three scans (on the centerline, 1 inch off the centerline and 2 inches off the centerline) yielded almost identical thickness results. The last scan (3 inches off the centerline of the duct) yielded the nominal thickness of the concrete wall. (The diameter of the steel duct was 3 inches.) Fully Grouted DuctPartiallyGrouted Duct Empty DuctCap with grout Center Line Scan 1” Off Center Line 2” Off Center Line 3” Off Center Line Figure 5-26. IE Thickness Results from IE Scanning off the Center Line of Steel Duct

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72 Impact echo scanning on Wall I Scanning across the ducts Several IE scans were performed transversely (horizontally) across both steel and plastic ducts. The first scan was performed at the bottom of the wall where both ducts were fully grouted. The results from the first scan are presented in Figure 5-27 and the wall nominal thickness was 9.7 inches. The thickness from fully grouted steel duct section was 11.1 inches and the thickness from the fully grouted plastic duct was 12.5 inches. The second scan was performed at the middle of the wall where both ducts were partially grouted and the results of the test are shown in Figure 5-28. In the partially grouted case, an average thickness of the partially grouted steel duct was 11.8 inches and an average thickness of the partially grouted plastic duct was 12.9 inches. Finally, the last scan was performed toward the top of the wall where both ducts were left empty and the thickness results are shown in Figure 5-29. In the empty case, the average thickness of the empty steel duct was 11.4 inches and the average thickness of the empty plastic duct was 12.3 inches. Center Line of Plastic DuctCenter line of steel duct wall Figure 5-27. IE Thickness Results from IE Scanning across Steel and Plastic Ducts – Fully Grouted Ducts

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73 Scanning across Steel and Plastic Ducts – Partially Grouted Ducts (Debonded) Scanning across Steel and Plastic Ducts – Empty Ducts Figure 5-28. IE Thickness Results from IE of Plastic DuctCenter line of steel duct Center Line Figure 5-29. IE Thickness Results from IE Center line of steel duct Center Line of Plastic Duct

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74 Spectral Analysis of Surface Waves (SASW) Test Results Several SASW tests were performed across the ducts with a receiver receiver spacing of 20 cm. The surface wave velocity vs. wavelength results from empty, partially grouted and fully grouted steel duct are shown in Figure 5-30. Review of this figure shows that the surface wave velocities at shallow depths (0 0.4 ft or 0 4.8 inches) from all three cases are similar. At deeper depths, it is apparent that the surface wave velocity from the fully grouted duct is slightly higher than the velocity obtained from partially grouted duct. The velocity from the partially grouted duct is also slightly higher that the velocity from the empty, ungrouted duct. Next, the SASW tests were performed across the plastic duct with the same receiverreceiver spacing of 20 cm. The surface wave velocity results from empty, partially grouted and fully grouted steel duct are shown in Figure 5-31. In this case, the Figure 5-30. Surface Wave Velocity Dispersion Curve Results from Steel Duct Empty Duct Partially Grouted Duct Fully Grouted Duct

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75 surface wave velocity from an empty plastic duct is slightly higher than velocity frompartially grouted plastic duct. The velocity from the fully grouted duct seems to be thlowest among the three. the e Three UTI tests were performed with UPV transducers (54 Kilo Hertz). The first ity The second test was performed across . Figure 5-31. Surface Wave Velocity dispersion Curve Results from Plastic Duct Ultrasonic tomography imaging (UTI) results Empty Duct Partially Grouted Duct Fully Grouted Duct test was performed across the fully grouted ducts (plastic and steel) and the veloc tomogram image result is shown in Figure 5-32. the partially grouted ducts and the tomography image result is shown in Figure 5-33. The last test was performed across the empty ducts and the result is shown in Figure 5-34

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76 The image results from all three cases showed locations of the top plastic and bottom steel ducts. However, the images did not show the details inside the ducts. This is likely due to the 3 inch long ultrasonic waves going around rather than through the ducts. A further complication may be due to the acoustic impedance (velocity times density) contrast between concrete, steel and plastic, which can result in most of the energy being reflected back from the ducts. Consequently, only a very weak signal may emerge from a duct. Fully Grouted Plastic Duct Fully Grouted Steel Duct Figure 5-32. Velocity Tomogram Image from Fully Grouted Steel and Plastic Ducts Partially Grouted Plastic Duct Partially Grouted Steel Duct Figure 5-33. Velocity Tomogram Image from Partially Grouted (Debonded) Steel and Plastic Ducts

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77 Empty Plastic Duct Empty Steel Duct Figure 5-34. Velocity Tomogram Image from Empty Steel and Plastic Ducts Table 5-3. UPVT Velocities in ft/ms for Fully Grouted, Partially Grouted and Empty Ducts. Fully Grouted Partially Grouted Empty Plastic 13.7 12.8 12.8 Metal 11.5 11.4 11.5 Table 5-3, shows that the velocities of different types of grouted ducts are almost the same; therefore, UPVT was not useful in testing the wall sample.

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78 PHASE III Research Investigation Scope This portion of the research focuses on Impact Echo (IE) with a scanning technology to expedite the field procedure. The Impact Echo Scanning technique requires only one-sided access. The results of this investigation are to provide data on the potential use of the methods in the field. The tests were performed using an Olson Freedom Data PC system and the data was processed by Olson Engineering, Inc. (Olson 2003). Summary of Findings Laboratory non destructive evaluation (NDE). Several IE scans were performed along and across the steel and plastic ducts over a period of 24 days. The purpose of this was to observe the effects of the curing grout within the ducts. Also, the IE scans were performed off the centerline of the duct to see duct diameter effects. Each day a calibration scan was also recorded of a sound wall section (no ducts). Results from IE scanning. At Day 1, the grout inside the ducts produced IE Scan results similar to the void section of duct in both the plastic and steel ducts. At day 4 and the first indication of a difference between true void and grouted section of the ducts could be seen. At day 24, scanning along the steel duct showed a change in thickness measured at approximately 2.1 ft, shifting from 11.6 in to 12.3 in. Scanning along the plastic duct showed a change in thickness measured at approximately 1.6 ft, shifting from 12.4 in to 13.0 in.

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79 Background During this portion of the research, only Impact Echo (IE) Scanning was used to evaluate the internal grout condition of steel and plastic ducts. The IE Scanning system is shown in Figure 5-35 below. The results from IE Scanning tests during the first phase of the research proved to be most promising among the technologies of IE Scanning, Ultrasonic Pulse Velocity Tomography (UPVT) and Spectral Analysis of Surface Waves. (SASW). IE Scanning Unit Data AcquisitionSystem Figure 5-35. Data Acquisition System with IE Scanning Device Wall Specimen II Only one mockup wall (Wall II), with one plastic duct (3 “ID.) and one steel duct (3" ID.), was used in this investigation. Wall II had both steel and plastic ducts inside which were half filled with grout. A schematic picture of the internal conditions of grout is shown in figure 5-36, and a picture of the walls is shown in Figure 5-37. The walls are 3 ft wide, almost 4 ft high and about 9 inches thick.

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80 Figure 5-36. Reinforced Concrete Dimensions and Duct Location Steel Duct Plastic Duct Wall II Wall I Figure 5-37. Concrete Walls with Steel and Plastic Ducts

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81 Lab Investigations and Test Results This section describes the lab investigation and the test results from IE Scanning on both the mock up wall. Each duct was half filled from the bottom of the duct. Please note that the vertical IE Scan results are shown inverted. Note that 0-ft is at the top of the scan, but actually represents the beginning point of the scan, or the bottom of the wall. Scans were performed starting from the bottom (~3" above the bottom of the wall) to the top of the wall (~3" below the top of the wall). Impact echo scanning calibration on wall II First, an Impact Echo scan was performed at a location on the concrete wall with no duct inside to calibrate for the IE velocity of the concrete wall. The thickness results of the first scan, with a typical frequency response from the concrete wall are shown in Figure 5-38. From the calibration, an IE velocity of 12,000 ft/sec was use in the Impact Echo test. The average wall thickness from Figure 5-38 is just under 10 inches. A value of 11,000 ft/sec was used during Phase II research, which yields slightly lower thickness. At 24 days, the calibration test is roughly identical to the calibration test at day 1, as shown in Figure 5-39 below. This indicates the velocity of the several month old wall was basically constant during the test period.

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82 Figure 5-38. Calibration Scan from Sunday, 12/29/02 Figure 5-39. Calibration Scan from Tuesday, 1/12/03

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83 Impact echo scanning across the ducts IE scans were run across both steel and plastic ducts. The scans were performed at the bottom half of the wall where both ducts were grouted. The results from the first scan (day 1) is presented in Figure 5-40. From Figure 5-40, the wall nominal thickness was 10 inches. The thickness from fully grouted steel duct was 12.4 inches and the thickness from the fully grouted plastic duct was 13.0 inches. Figure 5-40. Horizontal Scan from Sunday, 12/29/02 – Day 1 At 24 days, the horizontal test across the grouted ducts is similar to the horizontal test at day 1, as shown in Figure 5-41 below. The thickness from fully grouted steel duct now measures 11.6 inches, down from 12.4 inches. The thickness from the fully grouted plastic duct measures 12.4 inches, down from 13.0 inches.

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84 Figure 5-41. Horizontal Scan from Tuesday, 1/21/03 – Day 24 Impact echo scanning along the ducts Several IE scan tests were performed on Wall II along each duct. The IE scan below was performed along the center line of the steel duct, starting from the bottom (~3" above the bottom wall) to the top of the wall (~3" below the top wall). The thickness results and an example frequency response are shown in Figure 5-42. From the frequency and thickness results in Figure 5-42, it is seen that the peak frequency shifted to a lower value for the duct as compared to the calibration scan shown in Figure 5-38. This resulted in higher thickness value, 12.4 inches, from the nominally 10 inch thick wall. There is, however, no indication that the duct is grouted in the bottom half of the duct at day 1.

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85 Figure 5-42. Scan along Steel duct from Sunday, 12/29/02 – Day 1 At 24 days, the vertical test along the steel duct does show an indication of the grout in the bottom half of the duct, as shown in Figure 5-43. At approximately 2 feet, there is a break in the plot, indicating the beginning of the un-grouted section. The thickness from the un-grouted section of duct now measures 12.3 inches, as compared to 11.6 inches for the grouted section. Figure 5-43. Scan along Steel duct from Tuesday, 1/21/03 – Day 24

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86 An Impact Echo scan was then performed along the center line of the plastic duct. The thickness and example frequency results are shown in Figure 5-44. An average thickness reading from the plastic duct is 13.4 inches with an average peak frequency of 5350 Hz. This example also shows the frequency and thickness shift as compared to typical values for the concrete wall by itself. There is, however, no indication that the duct is grouted in the bottom half of the duct. Figure 5-44. Scan along Plastic duct from Sunday, 12/29/02 – Day 1 At 24 days, the vertical test along the plastic duct does show an indication of the grout in the bottom half of the ducts, as shown in Figure 5-45 below. At approximately 1.6 feet, there is a break in the plot, indicating the beginning of the grouted section. The thickness from the un-grouted section of duct now measures 13.0 inches, as compared to 12.5 inches for the grouted section.

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87 Figure 5-45. Scan along Plastic duct from Tuesday, 1/21/03 – Day 24 IE scanning off the center line Further testing was performed to see the effects of IE scanning when performed off the center line of the duct. Results from testing performed on 12/29/02 off the centerline of the steel and plastic ducts are shown in Figures. 5-46 and 5-47, respectively. Testing was performed 3 inches off the centerline of the ducts. From Figures 5-46 and 5 47, there are no clear indications of grouted versus un-grouted ducts from these tests on day 1.

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88 Figure 5-46. Off Centerline of Steel Duct from 12/29/02 – Day 1 Figure 5-47. Off Centerline of Plastic Duct from 12/29/02 – Day 1 Results from testing performed on 1/21/03 off the centerline of the steel and plastic ducts are shown in Figures 5-48 and 5-49, respectively. At the steel duct, a

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89 change in thickness is measured at approximately 2.1 ft, shifting from 11.6 in to 12.3 in. At the plastic duct, a change in thickness is measured at approximately 1.6 ft, shifting from 12.4 in to 13.0 in. The thickness measurements above and below each shift are consistent. Figure 5-48. Off Centerline of Steel Duct from 1/12/02 – Day 24

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90 Figure 5-49. Off Centerline of Plastic Duct from 1/21/03 – Day 24

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CHAPTER 6 CONCLUSIONS Results from IE Scans The results from IE tests showed the most promise for assessing grout conditions of all three tests. The IE thickness results and a shift in the IE peak frequency were used successfully to identify internal conditions of a steel duct. For a plastic duct, it was more difficult to identify grout conditions due to partial debonding conditions between the plastic duct and concrete wall. In this investigation, internal conditions of grouted ducts were successfully evaluated using the IE thickness results together with an impactechogram for steel or metal ducts. Results from SASW tests The SASW tests showed good promise for steel ducts. The surface wave velocity results from the fully grouted steel duct showed the highest velocity while the velocity results from the empty steel duct showed lowest velocity. However, the test results from the plastic duct did not yield similar results. The velocity results from the empty plastic duct appeared to be the highest and those from the fully grouted plastic duct appeared to be the lowest. Results from Pulse Velocity UPVT The image results from the Ultrasonic Pulse Velocity Tomography Imaging tests showed locations of the ducts in all three cases. Unfortunately, the image results did not 91

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92 show grout condition details inside the ducts. This is because the frequency of the transducers used in this investigation was 54 kHz which is standard for concrete. This range of frequency yielded a wavelength longer than the inside diameter of the ducts. Further tests should be done with higher frequency/shorter wavelength transducers. Impactechogram Impactechogram is a two dimensional intensity plot of amplitude-normalized IE frequency data. The normalized amplitudes are contoured in colors or a gray-scale. The plot provides more details in what is inside the concrete wall. The impactechogram was particularly useful for the internal grout evaluation of the fully grouted plastic duct where multiple fundamental frequencies occurred. Table 6-1. Summary of NDT Evaluation Advantages Disadvantages IE -Good for steel Easy to use Bad with plastic Bad with partially grouted SASW Good for steel Bad for plastic UPVT Detailed inside image Slow and laborious Interpretation Difficulty Wavelength matched with duct size

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CHAPTER 7 RECOMMENDATIONS Research recommendations include study of the effects of various size defects ranging from the cross-section to or less of the cross-section on IE scanning. We also recommend studying the application of Impactechograms, which display the frequency amplitudes of the IE scans. We further recommend further studies be conducted on partially grouted ducts. Voids in post-tensioned ducts are typically found at the top of the drape, and then only the top half or less of the duct is missing grout. The ability to identify this type of defect in the field is critical to the life span of any structure utilizing post-tensioning to mitigate the risk of long-term strand corrosion. The image results from UPVT images showed locations of both ducts clearly in all three cases. Unfortunately, the images did not show details inside the ducts. We suggest UPVT imaging tests be performed in the next investigation with higher frequency (shorter wavelength) UPV transducers (for example 150 KHz). The SASW results from steel ducts showed a potential use of the method. Unfortunately, the SASW test results from plastic ducts did not predict the internal grout conditions correctly. It is suggested that SASW tests be repeated on the plastic and metal ducts with several receiver test spacings of 10, 15 and 20 centimeters, for 3” I.D. ducts. 93

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APPENDIX A SAMPLE SURVEY Date: November 30, 2001 Alabama Department of Transportation Paul Bowlin, Transportation Director Alabama Department of Transportation 1409 Coliseum Blvd. Montgomery, AL 36130 (334) 242-6311 (334) 262-8041 Fax (334) 242-6319 Donald W. Vaughn, Administrative Engineer (334) 242-6318 Ray D. Bass, Chief Engineer Web Site: http://www.dot.state.al.us Dear Mr. Bowlin A team at the University of Florida’s School of Building Construction is currently involved in a research project aimed at identifying an accurate, convenient, and rapid non-destructive method of detecting defects in bonded post-tensioned ducts. It would be beneficial to our research if you would take a few moments to complete the attached survey. The survey is designed to inform us of the standard procedures that are incorporated by your organization. Your professional knowledge will help us in our future efforts, and we greatly appreciate your time and support. Please complete the enclosed questionnaire and mail your response by 31 Dec. 2001. A self-addressed envelope is provided for the convenient return of this information. Results of the survey will be provided to you upon completion of the project if you so desire. Sincerely, Dr. Larry C. Muszynski Mr. Elie Andary Assistant Professor Graduate Research Assistant 94

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95 Name_____________________________________ Date_________________ Position_________________________________________________________ Agency_________________________________________________________ Phone No._______________________________________________________ E-mail Address___________________________________________________ Agency’s WWW Address: http://____________________________________ The following survey contains five items and should take no more than 10 minutes to complete. Once again, thank you for your participation. Please check the following box if you would like the results of the survey sent to you. 1. Do you use post-tensioning systems in bridge construction in your state and what type? Unbonded yes no Bonded yes no 2. What type of duct material is generally used in your systems? Smooth plastic corrugated plastic smooth metal corrugated metal 3. If you are using bonded post-tensioning systems, what class of grout do you typically use? Class A Class B Class C Class D Other 4. Have you ever experienced failure of bonded post-tensioning tendons? Yes No if yes what was/were the cause(s)__________________________ _____________________________________________________________________ 5. Do you use Non-destructive inspection and/or testing methods to assess the integrity of the grout in your bonded post-tensioning systems? Yes No If yes, what type(s)_____________________________________________________ ________________________________________________________________________ ________________________________________________________________________ Thank You!

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APPENDIX B Raw Data from State Departments of Transportation Survey post-tensioning systems duct material Bonded Post-tensioning Grout class Non-destructive inspection Tendon's Failure DOT Name Symbol Respond Results Unbonded Bonded SP CP SM CM A B C D Yes No Yes No Alabama AL Alaska AK x x Arizona AZ x x x x x x x Arkansas AR x California CA x x x x x x x Colorado CO x x x x x x x x Connecticut CT x x x x x x x Delaware DE x Florida FL Georgia GA x x x x x x x Hawaii HI x x x x x x x Idaho ID x x x x x x x Illinois IL x x x x x x x x Indiana IN Iowa IA x x Kansas KS x x x x x x x Kentucky KY x x Louisiana LA x x x x x x x x Maine ME Maryland MD Massachusetts MA x x x x Michigan MI x x x x x x x Minnesota MN Mississippi MS x x x x x x x x Missouri MO Montana MT x x Nebraska NE Nevada NV New Hampshire NH x New Jersey NJ North Carolina NC District of Columbia DC New Mexico NM New York NY x x x x x x x x x x North Dakota ND x x x Ohio OH Oklahoma OK Oregon OR Pennsylvania PA x Rigid plastic x x x x Puerto Rico PR x Rhode Island RI South Carolina SC x x x x x x x x South Dakota SD Tennessee TN x x x x x x Texas TX x x x x x x x x x x x Utah UT x x x x x x x Vermont VT x Virginia VA Washington WA x x x x x x West Virginia WV x x x x x x x Wisconsin WI x x x Wyoming WY x x x x x x 96

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215 APPENDIX C Technical Data Guide MASTERFLOW'1205 High-performance grout for highly stressed steel Cementitious Grouts How to Apply MASTERFLOW 1205 Preparation Clean cables/strands of all oxidation, dirt, oil, or any loose materials. Ducts should be clean and free of an y defects. Description MASTERFLOW 1205 is specially formulated to produce a pumpable, nonbleeding, high-strength fluid product with extended working time for grouting. It provides corrosion protection for highly stressed steel cables, anchorage, and rods. MASTERFLOWO 1205 is formulated with a specially graded aggregate, which mitigates chloride migration while still allowing the product to be easily pumped long distance through small openings. Check proposed method of mixing and pumping to ensure continuous placement once pumping starts. It is recommended to have a source of high pressure water with connections for flushing grout hoses or partially grouted cable ducts in case the pumping must be interrupted. Test the pump and grout lines with water or pressurized oil-free air to confirm they are capable of providing and withstanding the required pressure, and to see that all connections are tight, without leaks. Loss of water from slow or nonmoving grout can result in a blocked line. Plug, ball or gate valves should be provided at the pump outlet, at the inlet ends of vertical cable ducts, and at both ends of the horizontal ducts. Also, a valued by-pass hose or pipe from the pump discharge line back to its hopper is strongly recommended. This will ensure grout recirculation from pump to hopper can be maintained during connection changes and other pumping delays. The inside diameter of the pipe, hose and valves, through which MASTERFLOW 1205 is to be pumped, should be at least 3/4 inches (19 mm) inside diameter to 2 inches (51 mm) inside diameter, consistent throughout the system. Avoid elbows if possible. The pump lines and grout line, if needed, may be flushed with high pH lime saturated water to lubricate and cool the ducts. This water will be displaced by the oncoming grout and discharged at the outlet end prior to obtaining the air free mixed grout. Collect the lime saturated water and use as mix water if needed. Collect the transitional grout and discard. Temperature The recommended temperature range of the grout as mixed should be 40F to 90F l4C to 32C). The duct temperatures should also be within the same temperature range. Special precautions should be followed for hot or cold weather. Higher temperatures increase the amount of mixing water needed for a given fluidity and limit working time. Lower temperatures induce bleeding, retard set and impede early strength gain, but permit reducing mixing water content for a given fluidity and increase ultimate strength. When duct temperatures are above 90F (32C), employ techniques to produce lower mixed grout temperature. Cool bags of MASTERFLOW• 1205 by storing in a shaded area or a cool place. Use cold potable water to attain the mixed grout at proper temperature. Be careful that you do not drop the grout temperature below 50F (4C). Ducts can also be cooled by circulating cold water. Lime (Ca OH,) can be added to the circulating water to increase pH to 12.4 to help passivate the steel and reduce the potential for steel oxidation prior to grouting. Features/Benefits Nonshrink materials Enhances flow and protects stress tendons, bolts, or bars from the threat of corrosion Can be pumped and/or recirculated for relatively long periods of time-Can be used at temperatures ranging from 40F to 90F (4C to 32C) Hardens without settlement shrinkage within the grout duct Ensures maximum bond and long-term protection against ingress of water and chlorides Meets all the compressive strength and nonshrink requirements of CRD C 621 and ASTM C 1107, at a fluid consistency Does not contain components that are detrimental to high strength steel; does not form hydrogen gas, carbon dioxide, or oxygen as an early expansion mechanism Meets requirements of PTI guide specifications Easy to pump or pour groutHardens without bleeding or settlement shrinkage and formation of voids Where to Use MASTERFLOW 1205 • Pumping into areas around post-tensioned cables and rods to encapsulate the steel, protecting it against corrosion and providing maximum anchorage 1 Placing around end sections of unanchored cables and rods, providing anchorage for subsequent tensioning • Filling voids in restricted spaces between wall panels, beams, and columns where grout will be in contact with highly stressed steel • Grouting cable anchor plates or other types of plates where grout will be in contact with highly stressed anchorages Important: read this first ChemRex' does not warrant the performance of this product unless the instructions of this document and other related ChemRex• documents are adhered to in all respects Pre job conference and Job service Conferences prior to the installation of the product should be held as early as practical. Such conferences are important to review the following recommendations (for a given grouting project) to ensure the placement of highest quality and lowest in-place cost. 3 03600 GROUTS Construction ChemicalsAmericos 97

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98 When duct temperatures are 40F (4C), the temperature of the mixed grout should be increased by mixing in warm potable water. Ducts can be heated by circulating warm water throughout ducts. Lime (Ca OH,) may be added to the mixing water to increase pH and lubricate duct. Do not exceed 90F (32C) temperatures when warming both the mixed grout and the duct. Mixing MASTERFLOW 1205 is a ready-to-use product requiring only the addition of potable water. Normal mixing water content is determined by the ASTM C 939 Grout Efflux Time of 20 to 30 seconds immediately after mixing, and attaining '0' bleeding in the modified ASTM C 940 Wick Induced Bleeding Test, using the specified mixer for mixing the grout at the job. Charge mixing vessel with 80% of the required water and add MASTERFLOW 1205 with mixer running. Mix a minimum of 3 minutes or until product has reached a uniform consistency. Add additional water as needed to attain correct efflux and mix an additional 2 minutes. Consult your ChemRex representative for special mixing instructions. Do not use water in an amount or at a temperature that will produce a flow of less than 20 seconds on the flow cone (ASTM C 939), or that will cause mixed grout to bleed or segregate. Jobsite conditions such as the size and complexity of the space to be grouted, pumping line diameters, height, mixing and pumping methods, and temperatures are factors that determine the actual amount of water needed. Have one or more mixers available with the capacity to allow mixing and pumping to proceed simultaneously and continuously. Place water in the mixer first, then steadily add the grout with mixer operating. Mix until the grout is homogeneous and free of lumps, which should be approximately 3 to 5 minutes, making sure all of the dry material is scraped from the mixer sides. Convey the mixed grout into the pump surge hopper and pass through a screen with 0.125 to 0.188 in. (3 mm to 5 mm) openings to catch possible lumps and then start pumping grout, after verifying grout efflux, into the duct. Note: Do not mix more grout than can be placed through a pump in 30 to 45 minutes, depending on temperature. Application Place MASTERFLOW 1205 in accordance with section C5.6.3 Grouting Operations as stated in the 'Guide Specification for Grouting of Post-Tension Structures' prepared by the PTI Committee on Grouting Specifications. Curing Cure all exposed grout areas by wet curing for 24 hours with clean, wet rags (do not use burlap), followed by the application of an ASTM C 309 compliant curing compound. In cold weather, keep grout temperature above 40F (4C) until final set. Thereafter, keep temperature above freezing until a compressive strength of 1500 psi (10 MPa) is attained prior to the first freeze. For Best Performance The walls of the space being grouted should be between 40F and 100F (4C and 38C) and should be saturated with lime water for optimum results. For use at temperatures above the range, consult ChemRex• Technical Service. DO NOT use mixing water in an amount or at a temperature that will produce a flow of less than 20 seconds (CRD C 611 or ASTM C 939) or cause the mixed grout to bleed or segregate when tested by the Modified Wick Induced Bleeding Test (ASTM C 940). ChemRex* is not responsible for stress corrosion caused by ingredients in the flushout, saturation or mixing water, or for contaminants either in the space being grouted or from other materials used in the system. The product contains Portland cement. Portland cement, in combination with water, may cause skin irritation, rash, and alkali burn. Do not wear contact lenses when working with this product. Remove soiled clothing and wash before reuse. Make certain the most current version of this data guide is being used; call Customer Service (1-800-433-9517) to verify the most current version. Proper application is the responsibility of the user. Field visits by ChemRex personnel are for the purpose of making technical recommendations only and are not for supervising or providing quality control on the jobsite. Technical Data Compliances Meets all compressive strength and settlement shrinkage requirements of CRD C 621 and ASTM C 1107 at a fluid consistency. Complies with Post Tensioned Institute recommendations for a prepackaged post tensioned steel duct grout. Typical Performance Data 0 70F (21"C) Flow (ASTM C 939) 20 25 sends Final set (ASTM C 953) <10 hours Volume change (ASTM C 1090) 1 day 28 days Prehardened expansion height <0.2% change @ 3 hours (ASTM C 940) Compressive strength (ASTM C 942) 1 day 3 days 7 days 28 days Chloride permeability <2,500 coulombs (ASTM C 1202) Modified PTI 30 Volts Acid soluble chloride content <0.08% by weight (ASTM C 1157) of cement )2,000 Psi (13.8 MPa) )4,000 PSI (27.6 MPa) )5.500 Psi (37.9 MPa) )8,000 PSI (55.2 MPa) > 0.0% >0.0% and <0.2% Gelman Pressure Bleed 10 minutes @ 30 psi 0 vertical rise of 6 ft. (1.6 m) maximum pressure Wick induced bleeding % bleed 0 3 hrs. (ASTM C 940. modified per PTD FHWA acce erated )1.600 hrs. corrosion test Reasonable variations from the results shown above can be expected. Field and laboratory tests should be controlled on the basis of the desired plating consistency rather than strictl y on water content.

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99 Waste Disposal Method This product when discarded or disposed of is not listed as a hazardous waste in federal regulations. Dispose of in a landfill in accordance with local regulations. For additional information on personal protective equipment, first aid, and emergency procedures, refer to the product Material Safety Data Sheet (MSDS) on the job site or contact the company at the address or phone numbers given below. Proposition 65 This product contains materials listed by the state of California as known to cause cancer, birth defects, or reproductive harm. VOC Content This product contains 0 g/L or 0 Ibs./gallon. For medical emergencies only, call ChemTrec (1/800/424-93001. Order Information Packaging MASTERFLOW 1205 • 55 lb. (25 kg) bags • 2,500 lb. (1,134 kg) bulk bags also available by special order Shelf Life • Shelf life is 6 months in original, unopened bags'stored under normal conditions. Coverage • One 55 Ib. l25 kg) bag yields approximately 0.55 ft.' (0.016 m) Caution MASTERFLOW' 1205 Risks Eye irritant. Skin irritant. Causes burns. Lung irritant. Precautions KEEP OUT OF THE REACH OF CHILDREN. Avoid contact with eyes. Wear suitable protective eyewear. Avoid prolonged or repeated contact with skin. Wear suitable gloves. Wear suitable protective clothing. Do not breathe dust. In case of insufficient ventilation, wear suitable respiratory equipment. Wash soiled clothing before reuse. First Aid Wash exposed skin with soap and water. Flush eyes with large quantities of water. If breathing is difficult, move person to fresh air.

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100 Limited Warranty Notice Every reasonable effort is made to apply ChemRex• exacting standards both in the manufacture of our products and in the information which we issue concerning these products and their use. We warrant our products to be of good quality and will replace or, at our election refund the purchase price of any products proved defective. Satisfactory results depend not only upon quality products, but also upon many factors beyond our control. Therefore, except for such replacement or refund, CHEMREX MAKES NO WARRANTY OR GUARANTEE, EXPRESS OR IMPLIED, INCLUDING WARRANTIES OF FITNESS FOR A PARTICULAR PURPOSE OR MERCHANZ4BILITY, RESPECTING ITS PRODUCTS, and CHEMREX* shall have no other liability with respect thereto. Any claim regarding product defect must be received in writing within one (1) year from the date of shipment. No claim will be considered without such written notice or after the specified time interval. User shall determine the suitability of the products for the intended use and assume all risks and liability in connection therewith. Any authorized change in the printed recommendations concerning the use of our products must bear the signature of the ChemRek Technical Manager. MBT mark used under license from MBT Holding AG Corporate office: 889 Valley Park Drive: Shakopee, MN 55379 Customer Service: 1/800/433-9517 Technical Services: 1/800/ChemRex (1/800/243-6739) Web Site: www.chemrex.com Form No. 1019403 For professional use only. 7M 1/02 2002 ChemRex Not for sale to or use by the general public. Replaces 1/01 Printed on recycled paper including 10% post-consumer fiber

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MATERIAL SAFETY DATA SHEET ChemRex, Inc. 24-Hr Emergency Commercial Construction Products Division CHEMTREC (800) 424-9300 889 Valley Park Drive Shakopee, MN 55379 Prepared by: Regulatory Affairs Department (612) 496-6000 Page: 1 of 4 Revision Date: 03/29/00 Reason for revision: Manufacturer name change This document is prepared pursuant to the OSHA Hazard Communication Standard (29 CFR 1910.1200). Where a proprietary ingredient is shown, the identity may be made available as provided in this standard. All components of this product are included in the EPA Toxic Substances Control Act (TSCA) Chemical Substance Inventory. 1. PRODUCT NAME: MASTERFLOW 1205 GROUT (Formerly: GS 1205) Chemical Family : Hydraulic Cement Compounds EXPOSURE LIMITS* 2. HAZARDOUS INGREDIENTS: CASNO TLV STEL PEL CONTENT Portland cement 65997-15-1 10 mg/m3 None None 55-65% Silica, Crystalline Quartz" 14808-60-7 3 mg/m3*** None **** 1-7% Calcium Oxide 1305-78-8 2 mg/m3 None 5 mg/m3 1-7% Silicon Dioxide, Amorphous 7631-86-9 3 mg/m3***** None None 1-7% *) Refer to Section 7 for available LD/LC(50) Health Hazard Data. **) Contains less than 0.1% w/w 53 micron or smaller Crystalline Quartz. (***) 0.1 mg/m3 respirable quartz (****) 10 mg/m3 divided by %Si02+2 (respirable quartz) (*****) Particulates NOC Respirable fraction. 3. PHYSICAL DATA: Boiling Point (oC): N/Ap Water/Oil Distribution Percent Volatile: 0 Coefficient: N/Ap Freezing Point (oC): N/Ap Solubility in Water: Slight Vapor Pressure mmHg @20 (oC): N/Ap Density: 93 Lb/Ft3 Vapor Density: N/Ap pH: N/Ap Odor Threshold: (ppm) N/Ap Evaporation Rate: N/Ap Appearance: Grayish granular powder Odor: Odorless N/Av = Not Available N/Ap = Not Applicable ca. = Approximate 4. FIRE AND EXPLOSION HAZARD DATA: HMIS Hazard Rating No. 0 (Minimal) APPENDIX D Material Safety Data Sheet 101

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102 MASTERFLOW 1205 GROUT Page 2 of 4 4. FIRE AND EXPLOSION HAZARD DATA: (cont'd) Auto-Ignition Temperature: Not Applicable Limits Of Flammability: LEL: Not Applicable UEL: Not Applicable Extinguishing Media: This material is non-flammable. Use extinguishing agent suitable for type of surrounding fire. Special Fire & Unusual Hazards: None known. 5. REACTIVITY DATA: HMIS Hazard Rating No. 0 (Minimal) Stability: Stable. Not sensitive to mechanical impact. Incompatibility: Strong mineral acids. Hydrofluoric acid slowly dissolves silicon dioxides (Silicon Tetrafluoride, a toxic substance, is formed.). Hazardous Decomposition Products: Nbne known. Hazardous Polymerization: Will not occur. 6. ENVIRONMENTAL AND DISPOSAL INFORMATION: Action to Take for Spills/Leaks : No special procedures are required for clean-up of spills or leaks of this material. Sweep up and return for reuse or discard. Waste Disposal Method : Does not contain hazardous chemicals as defined in 40 CFR 260. Dispose in a landfill in accordance with local, state, and federal regulations. 7. HEALTH HAZARD DATA: HMIS Hazard Rating No. 2 (Moderate) PRIMARY ROUTE OF ENTRY : Inhalation Effects Of Overexposure Inhalation : Nuisance dust can cause temporary but reversible respiratory problems. Eves : Abrasive action can cause damage to the outer surface of the eye. In combination with water can cause severe irritation with corneal injury. Skin Contact : Abrasive action can cause slight to moderate imitation. In combination with water dermal exposure can cause severe alkali bums. Skin Absorption : Does not absorb through skin. In eg stion : Not likely source of entry due to physical nature of material.

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103 MASTERFLOW 1205 GROUT Page 3 of 4 7. HEALTH HAZARD DATA: (cont'd) Chronic: Product does not contain carcinogenic materials as defined by OSHA Hazardous Communications Act 1910.1200 . Materials are not known mutagenic, teratogenic, or reproductive health hazards 8. FIRST AID: Inhalation: Remove victim from exposure. If difficulty with breathing, administer oxygen. If breathing has stopped administer artificial respiration, preferably mouth-to-mouth. Seek medical attention. Eves: Flush eyes with water, lifting upper and lower lids occasionally for 15 minutes. Seek medical attention. Skin: Remove contaminated clothing. Wash thoroughly with soap and water. If irritation persists seek medical attention. Wash contaminated clothing before reuse. In es~: Do NOT induce vomiting; give large quantities of water; get immediate medical attention. If vomiting occurs spontaneously, keep head below hips to prevent aspiration of liquids into lungs. Do NOT give anything by mouth to an unconscious person. 9. SPECIAL PROTECTION INFORMATION: Ventilation : Ventilation is recommended. Air movement must be designed to insure turnover at all locations in work area to avoid build up of airborne dust concentrations. Personal Protection Eguinment : Do NOT wear contact lenses when working with this material. Use chemical goggles/safety glasses with side shields and Rubber/Latex gloves. Selection of specific items such as boots and apron will depend on operation. Wear respirator protection whenever airborne concentrations exceed TLV ceilings or TWA, use NIOSH/OSHA approved respirators equipped with an organic vapor cartridge for listed hazard. Confined spaces, rooms, or tanks are areas where concern for TLV's is especially important. Reference OSHA Regulation CFR 29 1910.134 for recommended respiratory protection. 10. ADDITIONAL INFORMATION: Average Shelf Life: Refer to Product Data Sheet. Special Instructions: Store in cool, dry place. REGULATORY INFORMATION: Title III Section 302 : No reportable chemicals. Title III Section 311/312 : Health hazard: Immediate Physical hazard: None

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104 MASTERFLOW 1205 GROUT Pa g e 4 of 4 10. ADDITIONAL INFORMATION: ( cont'd ) REGULATORY INFORMATION: ( cont'd ) Title III Section 313 : State : California No re p ortable chemicals. This product contains a chemical known to the state of California to cause cancer . 14808-60-7 _< 0.1 Class D, Div. 2, Sub A Class D, Div. 2, Sub B Class E Silica , Cr y stalline Q uartz ( Res p irable ) WHMIS Classification : Canadian Domestic Substance List : TRANSPORTATION National Motor Frei g ht Classification ( NMFC ) : 42130 Sub: 2Class:50 Description: CEMENT, HYDRAULIC Emergency Response Guide Page No.: NOT REGULATED DOT Reportable Quantity: NOT REGULATED Marine Pollutant: NL P = Moderate NL= Not Listed PP = Severe ND = Not D ete r m i ned WS = Water Sheen The information herein is given in good faith. No warranty, expressed or implied, is given regarding the accuracy of these data or the results obtained from the use thereof. Consult ChemRex, Inc. for further information.

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LIST OF REFERENCES American Concrete Institute Committee 228, “Nondestructive Test Methods for Evaluation of Concrete in Structures” ACI 228.2R-98 (Section 2.2.4). Aouad, M.F., "Evaluation of Flexible Pavements and Subgrades Using the Spectral Analysis of Surface Waves Method", Dissertation Submitted in Partial Fulfillment of the Doctor of Philosophy Degree, The University of Texas at Austin, 1993. Chang, Y., Wang C., and Hsieh, C., Feasibility of Detecting Embedded Cracks in Concrete Structures by Reflection Seismology. NDT & E International. Vol. 34, 2001. Comparison of Pulse-Echo-Methods for Testing Concrete, http://www.ndt.net/article/concrete/concrete.htm, Vol. 1, No. 10, 1996. (9/19/2001) Florida Department of Transportation District 3,Mid-Bay Bridge Post-Tensioning Evaluation, 2001. Halabe, U., and Franklin, R., Detection of Flaws in Structural Members Using Spectral Analysis of Ultrasonic Signals. Nondestructive Testing and Evaluation. Vol. 15, No. 3, 1999. Karagouz, M., Bilgutay, N., Akgul, T., and Popovics, S., Ultrasonic Testing of Concrete Using Split Spectrum Processing. Materials Evaluation. Vol. 57, No. 11, 1998. Koehler, B., Hentges, G., Mueller W., A Novel Technique for Advanced Ultrasonic Testing of Concrete by Using Signal Conditioning Methods and a Scanning Laser Vibrometer. http://www.ndt.net/article/koehler2/koehler2.htm. Vol. 2, No. 7, 1997 (9/20/2001). Martin, J., Broughton, K.J., Giannopolous, A., Hardy, M.S.A., and Forde, M.C., Ultrasonic Tomography of Grouted Duct Post-tensioned Reinforced Concrete Bridge Beams. NDT & E International. Vol. 34, No. 2, 2001. Nazarian, S., and Stokoe, K.H., II, In Situ Determination of Elastic Moduli of Pavement Systems by SASW Method (Practical Aspects), Report 368-1F, Center For Transportation Research, The University of Texas at Austin, 1985. Nazarian, S., and Stokoe, K.H., II, In Situ Determination of Elastic Moduli of Pavement Systems by SASW Method (Theoretical Aspects), Report 437-2, Center For Transportation Research, The University of Texas at Austin, 1986. 105

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106 Olson Engineering, Inc., Internal Report, Phase II Nondestructive Testing Investigation Internal Grout Concrete Inside Steel and Plastic Post-tensioning Ducts, University of Florida, Olson Engineering Job No. 1211B, November 2002. Olson Engineering, Inc., Internal Report, Phase III Nondestructive Evaluation Research Internal Grout Conditions Inside Steel and Plastic Post-tensioning Ducts, University of Florida, Olson Engineering Job No. 1211B, February 2003. Popovics, J. S., Achenbach, J. D., and Song, W., Application of New Ultrasound and Sound Generation Methods for Testing Concrete Structures. Magazine of Concrete Research. Vol. 51, No. 1, 1999. Rens, K., Transue, D., and Schuller, P., Acoustic Tomographic Imaging of Concrete Infrastructure. Journal of Infrastructure Systems, March 2000. Roesset, J.M., Chang, D.W., and Stokoe, K.H., "Comparison of 2-D and 3-D Models for Analysis of Surface Waves Tests", Proceedings, Fifth International Conference on Soil Dynamics and Earthquake Engineering, Karlsruhe, Germany, 1991, pp. 111-126. Schokker, A., Koester, B., Breen, J., and Kreger, M. Development of High Performance Grouts for Bonded Post-tensioned Structures, Research Report 1405-2, Center For Transportation Research, The University of Texas at Austin, June 1999. Titman,T.J., Applications of Thermography in Non-destructive Testing of Structures. NDT & E International. Vol.34, No. 2, 2001. Wang, X., Chang C., and Fan L., Nondestructive Damage Detection of Bridges: A Status Review. Advances in Structural Engineering. Vol. 4, No. 2, 2001. Watanabe, T., Ohtsu, M., and Tomoda, Y., Impact-Echo Technique for Grouting Performance in Post-Tensioning Duct. J. Soc. Mat. Sci., Japan, Vol. 48, No.8, Aug. 1999. Yeih, W., and Huang, R., Detection of the Corrosion Damage in Reinforced Concrete Members by Ultrasonic Testing. Cement and Concrete Research. Vol. 28, No. 7, 1998.

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BIOGRAPHICAL SKETCH Elie George Andary was born in January 29, 1977, in Tripoli, Lebanon, to Asma N. Francis and George E. Andary. He has an older sister, Nadine, a younger sister, Aline, and a younger Brother, Nazih. He graduated from Bishmizzine High School in June 1995 and started his college career at the Lebanese American University in Byblos, Lebanon. He graduated with a bachelor’s degree of engineering in civil engineering in June of 2000. Although Elie was introduced to civil engineering he furthered his engineering knowledge by interning with some engineering companies. However, in 2001 Elie was influenced by construction management to pursue a Master of Science degree in Building Construction at the University of Florida in August 2003. After graduating from UF, Elie plans on a career in construction management with an interest in project management. The next goal in his professional career is to become a licensed Professional Engineer. 107