Coefficient of thermal and moisture expansion of concrete used in Florida

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Material Information

Title:
Coefficient of thermal and moisture expansion of concrete used in Florida
Physical Description:
xxi, 358 leaves : ill. ; 28 cm.
Language:
English
Creator:
Alungbe, Gabriel D., 1958-
Publication Date:

Subjects

Subjects / Keywords:
Concrete -- Moisture   ( lcsh )
Aggregates (Building materials) -- Moisture   ( lcsh )
Thermal stresses   ( lcsh )
Civil Engineering thesis Ph. D
Dissertations, Academic -- Civil Engineering -- UF
Genre:
bibliography   ( marcgt )
non-fiction   ( marcgt )

Notes

Thesis:
Thesis (Ph. D.)--University of Florida, 1989.
Bibliography:
Includes bibliographical references (leaves 346-356)
General Note:
Typescript.
General Note:
Vita.
Statement of Responsibility:
by Gabriel D. Alungbe.

Record Information

Source Institution:
University of Florida
Rights Management:
All applicable rights reserved by the source institution and holding location.
Resource Identifier:
aleph - 020978396
oclc - 22091263
System ID:
AA00022796:00001

Table of Contents
    Title Page
        Page i
    Dedication
        Page ii
    Acknowledgement
        Page iii
        Page iv
    Table of Contents
        Page v
        Page vi
        Page vii
        Page viii
    List of Tables
        Page ix
        Page x
        Page xi
        Page xii
        Page xiii
        Page xiv
        Page xv
    List of Figures
        Page xvi
        Page xvii
        Page xviii
        Page xix
    Abstract
        Page xx
        Page xxi
    Chapter 1. Introduction
        Page 1
        Page 2
        Page 3
    Chapter 2. Literature review
        Page 4
        Page 5
        Page 6
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        Page 28
        Page 29
    Chapter 3. Development of a laboratory testing procedure for measuring length change of concrete
        Page 30
        Page 31
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        Page 33
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        Page 40
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        Page 44
        Page 45
    Chapter 4. Testing program
        Page 46
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        Page 49
        Page 50
        Page 51
        Page 52
        Page 53
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    Chapter 5. Materials
        Page 57
        Page 58
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        Page 60
        Page 61
        Page 62
        Page 63
        Page 64
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    Chapter 6. Experimental designs of the laboratory study
        Page 67
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        Page 73
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    Chapter 7. Compressive strength of laboratory concrete specimens
        Page 80
        Page 81
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    Chapter 8. Splitting tensile strength of laboratory concrete specimens
        Page 118
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    Chapter 9. Modulus of rupture of laboratory concrete specimens
        Page 141
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    Chapter 10. Static modulus of elasticity of laboratory concrete specimens
        Page 164
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    Chapter 11. Coefficient of linear thermal expansion of laboratory concrete specimens
        Page 189
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    Chapter 12. Coefficient of moisture expansion of laboratory concrete specimens
        Page 215
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    Chapter 13. Results of in-service concrete study
        Page 229
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    Chapter 14. Development of prediction equations for concrete properties
        Page 254
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        Page 273
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        Page 275
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    Chapter 15. Optimization of concrete mix design for concrete pavement
        Page 277
        Page 278
        Page 279
        Page 280
        Page 281
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        Page 283
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    Chapter 16. Conclusions and recommendations
        Page 288
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    Appendix A. Mix proportions of concrete mixes
        Page 299
        Page 300
        Page 301
    Appendix B. Properties of fresh concrete
        Page 302
        Page 303
        Page 304
    Appendix C. Length readings of water-saturated laboratory concrete specimens
        Page 305
        Page 306
        Page 307
        Page 308
        Page 309
        Page 310
    Appendix D. Length readings of oven-dried laboratory concrete specimens
        Page 311
        Page 312
        Page 313
        Page 314
        Page 315
        Page 316
    Appendix E. Length readings of partially-saturated laboratory concrete specimens
        Page 317
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    Appendix F. Length readings of water-saturated in-service concrete specimens
        Page 334
        Page 335
        Page 336
    Appendix G. Length readings of oven-dried in-service concrete specimens
        Page 337
        Page 338
        Page 339
        Page 340
    Appendix H. Length readings of partially-saturated in-service concrete specimens
        Page 341
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        Page 343
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    References
        Page 346
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    Supplementary bibliography
        Page 350
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    Biographical sketch
        Page 357
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        Page 360
        Page 361
Full Text











COEFFICIENT OF THERMAL AND MOISTURE EXPANSION
OF CONCRETE USED IN FLORIDA












By

GPABRIEL D. ALUNGBE




















A DISSERTATION PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT
OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY UNIVERSITY OF FLORIDA 1989





























Dedicated to the loving memory of my father, Mr. Awusa Oshen,

who passed away while I was still a fetus.















ACKNOWLEDGEMENTS



I extend a special acknowledgement to Dr. Mang Tia who served in the capacity of chairman of my supervisory committee. He meticulously guided me and provided copious support through the entire stages of th project. His counsel was unparalleled. Dr. David G. Bloomquist, cochairman of my supervisory committee, provided myriad hours of support and guidance. Special thanks are extended to him. Further gratitude is extended to Dr. Byron E. Ruth, Mr. Torbjorn (Toby) J. Larsen, and Dr. Andrawus 1. Khuri for having given generously of their expertise and time and for serving on my supervisory committee.

This project would not have been possible without the financial support provided by the Florida Department of Transportation (FOOT). They also provided some materials used in this project. I unequivocally say thank you. To Dr. Jamshid Armaghani and Mr. Toby Larsen both of Materials Office (formerly Bureau of Materials and Research) at FOOT Gainesville, who worked incessantly for the approbation of this project, I am very grateful .

I would like to thank all the students and engineering technicians who assisted me in this research, and all my friends, especially Prasit Soongswang, whose assistance contributed to the successful completion of this project.

Mr. Daniel Richardson fabricated some of the equipments used in this research. To him I say thank you very much. A special thank you



iii








is also extended to the incomparable Mrs. Irene R. Scarso who meticulously and skillfully typed the manuscript.

Finally, I would like to thank my mother and grandmother, Mrs.

Victoria E. Ebagu and Ms. Qmiku Odugbo, respectively. Their enduring support and guidance are highly appreciated. And I thank my uncles Messrs. Nathy A. Oshen and Linus E. Okom for their support. To the governments of the Cross River State and Federal Republic of Nigeria who financed my bachelor's and master's studies, my heartfelt thanks are extended. I also acknowledge God for making all this possible.




































iv














TABLE OF CONTENTS


PAGE

ACKNOWLEDGEMENTS ................................ oiii

LIST OF TABLES .................................... so ............... viii

LIST OF FIGURES ............................. o ....... so ........... o ... xv

ABSTRACT .......... oo..* .... o ..... o..*o ... ........ xix

CHAPTER

1 INTRODUCTION ............................ o.oooooo .........

1.1 Background ................................................ 1
1.2 Objectives of the Study .............................. see.

2 LITERATURE REVIEW ................. *o* ... ..... It

2.1 Thermal Properties ........................................ 4
2.2 Test Methods ............................................. 12
2.3 Factors Affecting Coefficient of Thermal Expansion
of Concrete .............................................. 21
2.4 Effects of Thermal Expansion on Pavements ................ 29

3 DEVELOPMENT OF A LABORATORY TESTING PROCEDURE FOR MEASURING
LENGTH CHANGE OF CONCRETE ..................................... 30

3.1 Introduction ............................................. 30
3.2 Test Equipment ............................... ... 1,
3.3 Test Specimens ...........................................
3.4 Test Procedures ..........................................

4 TESTING PROGRAM ................ # ........ so* ....... o..%*..****.46

4.1 Laboratory Testing Program ............................... 46
4.2 Study of In-Service Concrete ............................. 55

5 MATERIALS ......................... *.so ......... *so ..... o ...... 57

5.1 Cements .................................................. 57
5.2 Aggregates ............................................... 57
5.3 Admixtures ............................................... 64
5.4 Epoxy .................................................... 64



v









6 EXPERIMENTAL DESIGNS OF THE LABORATORY STUDY .................. 67

6.1 Introduction ............................................. 67
6.2 Design No. I ............................................. 69
6.3 Design No. 2 ............................................. 70
6.4 Design No. 3 ............................................. 70
6.5 Design No. 4 ............................................. 74
6.6 Design No. 5 ............................................. 74
6.7 Design No. 6 ............................................. 74
6.8 Design No. 7 ............................................. 78

7 COMPRESSIVE STRENGTH OF LABORATORY CONCRETE SPECIMENS ......... 80

7.1 Introduction ............................................. 80
7.2 Experimental Results ..................................... R!"
7.3 Analysis of Results ..........................................
7.4 Summary of Findings ..................................... 108

3 SPLITTING TENSILE STRENGTH OF LABORATORY CONCRETE
SPECIMENS ....................... ......... ** ....... *118

8.1 Introduction ............................................ 118
8.2 Analysis of Results ..................................... 118
8.3 Summary of Findings ..................................... 140

9 MODULUS OF RUPTURE OF LABORATORY CONCRETE SPECIMENS .......... 1 1

9.1 Introduction ............................................ 141
9.2 Analysis of Results ..................................... 141
9.3 Summary of Findings ..................................... 163

10 STATIC MODULUS OF ELASTICITY OF LABORATORY CONCRETE
SPECIMENS ................................................ 0 ... 164

10.1 Introduction ........................................... 164
10.2 Analysis of Results .................................... I
10.3 Summary of Findings .................................... 1

11 COEFFICIENT OF LINEAR THERMAL EXPANSION OF LABORATORY
CONCRETE SPECIMENS ................. ot ..... *** ...... ***..*o ... 189

11.1 Introduction ........................................... 189
11.2 Experimental Results ............................... ..189
11.3 Analysis of Results ................................ ::..189
11.4 Summary of Findings .................................... 214

12 COEFFICIENT OF MOISTURE EXPANSION OF LABORATORY CONCRETE
SPECIMENS ....................................... ... .... e.t.215

12.1 Introduction ........................................... 215
12.2 Calculation of Coefficient of Moisture Expansion ....... 215 12.3 Analysis of Results .................................... 218
12.4 Summary of Findings .................................... 222



vi









13 RESULTS OF IN-SERVICE CONCRETE STUDY ................. ... ....229


13.2 Compressive Strength Test Results ...................... 229
13.3 Splitting Tensile Strength Test Results ................ 232
13.4 Static Modulus of Elasticity Test Results .............. 236
13.5 Results of Linear Thermal Expansion on In-Service

13.6 Results of Moisture 'Expansion of In-Service Concrete ... 243 13.7 Graphical Representation of Means ...................... 246
13.3 Summary of Findings ... ....... .. ... .... ..... .... .. ... ... 246

14 DEVELOPMENT OF PREDICTION EQUATIONS FOR CONCRETE PROPERTIES..254

14.1 Introduction ........................................... 25A
14.2 Relationship Between the Compressive and Splitting
Tensile Strengths. ............... .. ... ......25
14.3 Relationship Between the Compressive Strength and
Modulus of Rupture ..................................... 257
14.4 Relationship Between the Compressive Strength and
Static Modulus of El asticity. ........ .. ...... ....... ....261
14.5 Relationship Between the Splitting Tensile Strength
and Modulus of Rupture ............... *.*o.*.........264
14.6 Prediction of Coefficient of Linear Thermal Expansion
of Concrete .................................14.7 Prediction of Coefficient of Moisture Expansion ........ 273
14.3 Summary of Findings .......... ... *. ... ... .***&27

15 OPTIMIZATION OF CONCRETE MIX DESIGN FOR CONCRETE PAVEMENT .... 277

15.1 Introduction .................. .............. 7
15.2 Effects of Thermal Expansion and Modulus of Elasticity

15.3 Optimizing Concrete Pavement Mix Design ................ 281

16 CONCLUSIONS AND RECOMME14DATIONS .............. *.............288


16.3 Recommendations. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. ... ..... 297
16.4 Recommendations for Further Research ................... 29

APPENDICES

A MIX PROPORTIONS OF CONCRETE MIXES .... ....... ...... . ..300

B PROPERTIES OF FRESH CONCRETE ................... *.*..... ....303

C LENGTH READINGS OF WATER-SATURATED LABORATORY CONCRETE


D LENGTH READINGS OF OVEN-DRIED LABORATORY CONCRETE




vii









E LENGTH READINGS OF PARTIALLY-SATURATED LABORATORY CONCRETE
SPECIMENS .....................GS OFWA.....TER.SAURATEDI

F LENGTH READINGS OF WATER-SATURATED IN-SERVICE CONCRETE
SPECIMENS ..... ............. ........................... 338

G LENGTH READINGS OF OVEN-DRIED IN-SERVICE CONCRETE
SPECIMENS ...................... ... .. ... .......... ... 338
H LENGTH READINGS OF PARTIALLY-SATURATED IN-SERVICE CONCRETE
SPECIMENS ............... . . . . . . . . . 4

REFERENCES .................... *...... ......... .. . ... ..... 0346

SUPPLEMENTARY BIBLIOGRAPHY ..........................................35Q

BIOGRAPHICAL SKETCH ............ ............. 357






































viii














LIST OF TABLES


TABLE PAGE

2.1 Change in Moisture Content and Corresponding Change in Length as Reported by Matsumoto ............................... 16

2.2 Properties of Concrete Mixes Used by Saemann and Washa ........ I?

2.3 Reported Coefficients of Linear Thermal Expansion of Various Rocks ................................................. 23

2.4 Reported Coefficients of Linear Thermal Expansion of a Few More Important Rock Minerals .......

3.1 Typical Length Readings for Four Different Environmental
Conditions .................................................... 44

4.1 Mix Combinations for the Laboratory Study ..................... Q.;

4.2 Tests to be Performed on Each Batch of Concrete ............... 49

5.1 Results of Physical Tests on Cement Used ...................... 58

5.2 Results of Chemical Analyses on Cement Used ................... 59

5.3 Physical Properties of Coarse Aggregates ...................... 60

6.1 Factors, Levels, and Interactions for the Partial Factorial
Experiment .....................................

6.2 Design for Test on Effects of Aggregate Type, W/C Ratio at
Variable Cement Content, and Curing Duration (Design No. 1) ... 71

6.3 Design for Test on Effects of Aggregate Type and Curing
Duration at W/C of 0.53 and Cement Content of 508 lb/cy
(Design No. 2) ................................................ 72

6.4 Design for Test on Effects of Aggregate Type and Curing
Duration at W/C of 0.45 and Cement Content of 564 lb/cy
(Design No. 3) ................................................ 73

6.5 Design for Test on Effects of Aggregate Type and Curing
Duration at W/C of 0.33 and Cement Content of 752 lb/cy
(Design No. 4) ................................................ 75




ix









6.6 Design for Test on Effects of Cement Content and Curing
Duration Given W/C of 0.53 and Brooksville Limestone
(Design No. 5) ................................................ 76

6.7 Design for Test on Effects of Cement Content and Curing
Duration Given W/C of 0.45 and Brooksville Limestone
(Design No. 6) ................................................ 77

6.8 Design for Test on Effects of W/C Ratio and Curing Duration
Given Brooksville Limestone and Cement Content of 658 lb/cy
(Design No. 7) ................................................ 79

7.1 Results of Compressive Strength Test on Hardened Concrete.....81

7.2 Expected Mean Square Algorithm for Design No. I ...............

7.3 Expected Mean Square Algorithm for Design Nos. 2 4.00*0*00.*90 7.4 Expected Mean Square Algorithm for Design Nos. 5 and 6 ........ 91 7.5 Expected Mean Square Algorithm for Design No. 7 ............... 92

7.6 Results of ANOVA on Data From Compressive Strength Test in
Design No. I .........

7.7 Grouping of Aggregate Type by Means of Compressive Strength
of Concrete From Duncan's Test (Design No. 1) ................. 96

7.8 Grouping of Water-Cement Ratio by Means of Compressive
Strength of Concrete From Duncan's Test (Design No. 1) ........ 97

7.9 Grouping of Curing Duration by Means of Compressive Strength
of Concrete From Duncan's Test (Design No. 1) ................. 98

7.10 Results of ANOVA on Data From Compressive Strength Test in
Design No. 2 ................................................. 16"

7.11 Grouping of Aggregate Type by Means of Compressive Strength
of Concrete From Duncan's Test (Design No. 2) ................ 101

7.12 Results of ANOVA on Data From Compressive Strength Test in
Design No. 3 ................................................. 102

7.13 Grouping of Aggregate Type by Means of Compressive Strength
of Concrete From Duncan's Test (Design No. 3) ................ 104

7.14 Results of ANOVA on Data From Compressive Strength Test in
Design No. 4 .......................

7.15 Grouping of Aggregate Type by Means of Compressive Strength
of Concrete From Duncan's Test (Design No. 4) ................ 106





x








7.16 Results of ANOVA on Data From Compressive Strength Test in
Design No. 5 ................................................. 197

7.17 Results of ANOVA on Data From Compressive Strength Test in
Design No. 6 ................................................. 109

7.18 Results of ANOVA on Data From Compressive Strength Test in
Design No. 7 ................................................. 110

3.1 Results of Splitting Tensile Strength Test on Hardened
Concrete ..................................................... 120

8.2 Results of ANOVA on Data From Splitting Tensile Strength
Test in Design No. I ......................................... 122

8.3 Grouping of Aggregate Type by Means of Splitting Tensile
Strength of Concrete From Duncan's Test (Design No. 1),,,,,,,123

8.4 Grouping of Water-Cement Ratio by Means of Splitting Tensile
Strength of Concrete From Duncan's Test (Design No. 1),,,,,.,124

8.5 Results of ANOVA on Data From Splitting Tensile Strength
Test in Design No. 2 ...............

3.6 Results of ANOVA on Data From Splitting Tensile Strength
Test in Design No. 3 ......................................... 127

3.7 Grouping of Aggregate Type by Means of Splitting Tensile
Strength of Concrete From Duncan's Test (Design No. 3).......128

8.8 Results of ANOVA on Data From Splitting Tensile Strength
Test in Design No. 4 ......................................... 129

3.9 Results of ANOVA on Data From Splitting Tensile Strength
Test in Design No. 5 .................

3.10 Results of ANOVA on Data From Splitting Tensile Strength
Test in Design No. 6 ...................

3.11 Results of ANOVA on Data From Splitting Tensile Strength
Test in Design No. 7 ...............

9.1 Results of Moduli of Rupture Test on Hardened Concrete ....... 142

9.2 Results of ANOVA on Data From Modulus of Rupture Test in
Design No. 1 ................................................. 145

9.3 Grouping of Aggregate Type by Means of Modulus of Rupture
of Concrete From Duncan's Test (Design No. 1) ................ 146

9.4 Grouping of Water-Cement Ratio by Means of Modulus of Rupture
of Concrete From Duncan's Test (Design No. 1) ................ 147




xi








9.5 Results of ANOVA on Data From Modulus of Rupture Test in

9. Desults Nof AN2 onDtaFomMduu.f.utueTeti

9.7 Results of ANOVA on Data From Modulus of Rupture Test in



9.8 Grouping of Aggregate Type by Means of Modulus of Rupture
of Concrete From Duncan's Test (Design No. 4) .......... o....152

9.9 Results of ANOVA on Data From Modulus of Rupture Test in

9.0 Desults Nof.NV on Data....... F om. Modulus.... of Ruptur Tes5i

9.11 Results of ANOVA on Data From Modulus of Rupture Test in

101 Desults Nof Moulus of.. Elsict Test on Hardene C~**o9 *oncrete.165

910. Results of ANOVA on Data From Modulus of Elaticit Test i
inDesign No. 7.... ..............................17


10.3 Rosuping of Aggregn at Typrbymeao Modulus of Elasticity s

of Concrete From Duncan's Test (Design No. 1) ............... 168

10.4 Grouping of Water-Cement Ratio by Means of Modulus of Elasticity of Concrete From Duncan's Test (Design No. 1) ........ 169 10.5 Results of ANOVA on Data 'From Modulus of Elasticity Test
in Design No. 2 ........ o o.o .....................17

10.6 Grouping of Aggregate Type by Means of Modulus of Elasticity
of Concrete From Duncan's Test (Design No. 2).,............. 172

10.7 Results of ANOVA on Data From Modulus of Elasticity Test
in Design No. 3 3...... ............... o...... ................. 173

10.8 Grouping of Aggregate Type by Means of Modulus of Elasticity
of Concrete From Duncan's Test (Design No. 3) ............o..174

10.9 Results of ANOVA on Data From Modulus of Elasticity Test
in Design No. 4 .........................16

10.10 Grouping of Aggregate Type by Means of Modulus of Elasticity
of Concrete From Duncan's Test (Design No. 4) ...... o........ 177

10.11 Results of ANOVA on Data From Modulus of Elasticity Test





xii









10.12 Results of ANOVA on Data From Modulus of Elasticity Test


10.13 Results of ANOVA on Data From Modulus of Elasticity Test
in Design No. 7 .................................8

11.1 Results of Coefficient of Linear Thermal Expansion Test
on Water-Saturated Concrete Specimens...... .. . .... .. ...190

11.2 Results of Coefficient of Linear Thermal Expansion Test
on Oven-Dried Concrete Specimens. .............. *9**...... *1

11.3 Result of PROC MEANS on Paired Comparison of Single Sample


11.4 Mean, Standard Error of the Mean, and 95% Comfidence Inteval
of Coefficient of Thermal Linear Expansion Results .......... 196 11.5 Results of ANOVA on Data From Coefficient of Linear Thermal
Expansion Test on Water-Saturated Concrete Specimen in


11.6 Grouping of Aggregate Type by Means of Coefficient of Linear
Thermal Expansion of Water-Saturated Concrete From Duncan's
Test (Design No. 1). ......................

11.7 Results of ANOVA on Data From Coefficient of Linear Thermal
Expansion Test on Water-Saturated Concrete Specimen in


11.8 Results of ANOVA on Data From Coefficient of Linear Thermal
Expansion Test on Water-Saturated Concrete Specimen in


11.9 Results of ANOVA on Data From Coefficient of Linear Thermal
Expansion Test on Oven-Dried Concrete Specimens in Design


11.10 Grouping of Aggregate Type by Means of Coefficient of Linear
Thermal Expansion of Oven-Dried Concrete From Duncan's Test


11.11 Results of ANOVA on Data From Coefficient of Linear Thermal
Expansion Test on Oven-Dried Concrete Specimens in Design


11.12 Results of ANOVA on Data From Coefficient of Linear Thermal
Expansion Test on Oven-Dried Concrete Specimens in Design


12.1 Results of Moisture Expansion of Concrete Specimens ......... 216 12.2 Results of ANOVA on Data From Moisture Expansion of Concrete
Specimens in Design No. 3 ...... ..... o...... ....


xiii








12.3 Grouping of Aggregate Type by Means of Coefficient of Moisture
Expansion From Duncan's Test (Design No. 1) ................. 220

12.4 Results of ANOVA on Data From Moisture Expansion of Concrete
in Design No. 5 ............................................. 221

12.5 Results of ANOVA on Data Front Moisture Expansion of Concrete
in Design No. 6 ....................

12.6 Results of ANOVA on Data From Moisture Expansion of Concrete
in Design No. 7 ....................

13.1 Sites of In-Service Concrete Pavement Study ................. 230

13.2 Compressive Strength of In-Service Pavement Concrete ........ 231 13.3 Mean Splitting Tensile Strength of In-Service Pavement
Concrete ...........

13.4 Modulus of Elasticity of In-Service Pavement Concrete ....... 237 13.5 Comparison of Measured and Estimated Static Moduli of
Elasticity of Concrete ............

13.6 Results of Coefficient of Linear Thermal Expansion Test on
Water-Saturated In-Service Concrete ......................... 239

13.7 Results of Coefficient of Linear Thermal Expansion Test on
Oven-Dried In-Service Concrete .............................. 241

13.3 Results of T Test on the Difference Between the Coefficient
of Thermal Expansion at Water-Saturated and Oven-Dried
Conditions .................................................. 244

13.9 Results of Moisture Expansion Test on In-Service Concrete ... 245 14.1 Regression Coefficients for Relation Between Compressive and
Splitting Tensile Strength at 28-Day Moist Curing ........... 256

14.2 Regression Coefficients for Relation Between Compressive and
Modulus of Rupture at 28-Day Moist Curing ................... 260

14.3 Regression Coefficients for Relation Between Compression
Strength and Static Modulus of Elasticity at 28-Day Moist
Curing ..........

14.4 Regression Coefficients for Relation Between the Splitting
Tensile Strength and Modulus of Rupture at 23-Day Moist
Curing ...........

14.5 Coefficient of Linear Thermal Expansion of Water-Saturated
Laboratory Concrete Per Strength Class ...................... 270




xiv








14.6 Coefficient of Linear Thermal Expansion of Oven-Dried Laboratory Concrete Per Strength Class ............................ 271

14.7 Combined Water-Saturated and Oven-Dried Coefficient of Linear
Thermal Expansion of Laboratory Concrete Specimens Per
Strength Class .................. ............272

14.8 Coefficient of Moisture Expansion of Laboratory Concrete Per
Strength Class .............................................. 274

14.9 Coefficient of Moisture Expansion of In-Service Concrete .... 275

15.1 Computed Maximum Longitudinal Stress Using FEACONS IV
Program .........

15.2 Computed Maximum Load-Induced Stresses and Stress Ratios
Using Mean 28-Day Values of Modulus of Rupture, Modulus of
Elasticity, and Water-Saturated Coefficient of Thermal
Expansion of Laboratory Concrete ............................ 286

16.1 Range of Coefficient of Linear Thermal Expansion of WaterSaturated Laboratory Concrete ............................... 292

16.2 Range of Coefficient of Linear Thermal Expansion of OvenDried Laboratory Concrete ................................... 293

16.3 Range of Coefficient of Linear Thermal Expansion of Laboratory Concrete at Water-Saturated and Oven-Dried Conditions..294

16.4 Range of Coefficient of Moisture Expansion of Laboratory
Concrete .................................................... 295

16.5 Range of Coefficient of Moisture Expansion of In-Service
Concrete .................................................... 296





















xv














LIST OF FIGURES


FIGURE PAGE

2.1 Uniform Expansion of Concrete ................................. 6

2.2 Linear Expansion of Solid ...........

3.1 Length Comparator .... o.oo ..........

3o2 Water Tank. ...........

30 Forced Draft Oven .....

3.4 Specimen Mold ...................

3.5 Concrete Specimen with Embedded Thermocouples ................ 39

5.1 Gradation Chart for Brooksville Limestone #89 Coarse
Aggregate Used in Batches 1-12 [301 .......................... 61

5.2 Gradation Chart for Calera Coarse Aggregate [281 ............. 62

5.3 Gradation Chart for the River Gravel Coarse Aggregate [28] ... 63

5.4 Gradation Chart for Goldhead Sand Used in Batches 1-19 [281 .............

5.5 Gradation Chart for Goldhead Sand Used in Batches 20-24 ...... 66

7.1 Influence of Water/Cement Ratio and Moist Curing Duration on
Concrete Strength Using Brooksville Limestone... o ........... 111

7.2 Influence of Water/Cement Ratio and Moist Curing Duration on
Concrete Strength Using Dense Limestone ..................... 112

7.3 Influence of Water/Cement Ratio and Moist Curing Duration on
Concrete Strength Using River Gravel ........................ 113

7.4 Influence of Aggregate Type and Moist Curing Duration on
Concrete Strength at W/C = 0.33 ............................. 114

7.5 Influence of Aggregate Type and Moist Curing Duration on
Concrete Strength at W/C = 0.45 ............

7.6 Influence of Aggregate Type and Moist Curing Duration on
Concrete Strength at W/C = 0.53 .....


xvi









3.1 Influence of Water/Cement Ratio and Moist Curing Duration on Splitting Tensile Strength of Concrete Using Brooksville
Limestone ................................................... 134

8.2 Influence of Water/Cement Ratio and Moist Curing Duration on Splitting Tensile Strength of Concrete Using Dense
Limestone ................................................... 135

8.3 Influence of Water/Cement Ratio and Moist Curing Duration
on Splitting Tensile Strength of Concrete Using River
Gravel ...............................

8.4 Influence of Aggregate Type and Moist Curing Duration on
Splitting Tensile Strength of Concrete at W/C = 0.33 ........ 137

8.5 Influence of Aggregate Type and Moist Curing Duration on
Splitting Tensile Strength of Concrete at W/C = 0.45 ........ 138

8.6 Influence of Aggregate Type and Moist Curing Duration on
Splitting Tensile Strength of Concrete at W/C = 0.53 ........ 139

9.1 Influence of Water/Cement Ratio and Moist Curing Duration
on Modulus of Rupture of Concrete Using Brooksville
Limestone .......................

9.2 Influence of Water/Cement Ratio and Moist Curing Duration
on Modulus of Rupture of Concrete Using Dense Limestone ..... 156

9.3 Influence of Water/Cement Ratio and Moist Curing Duration
on Modulus of Rupture of Concrete Using River Gravel ........ 159

9.4 Influence of Aggregate Type and Moist Curing Duration on
Modulus of Rupture of Concrete at W/C = 0*339......160

9.5 Influence of Aggregate Type and Moist Curing Duration on
Modulus of Rupture of Concrete at W/C = 0.45 .......... 00.9.0,1

9.6 Influence of Aggregate Type and Moist Curing Duration on
Modulus of Rupture of Concrete at W/C = 0.53 ................ 162

10.1 Influence of Water/Cement Ratio and Moist Curing Duration
on Modulus of Elasticity of Concrete Using Brooksville
Limestone ................................................... 182

10.2 Influence of Water/Cement Ratio and Moist Curing Duration on
Modulus of Elasticity of Concrete Using Dense Limestone ..... 183

10.3 Influence of Water/Cement Ratio and Moist Curing Duration on
Modulus of Elasticity of Concrete Using River Gravel ........ 184

10.4 Influence of Aggregate Type and Moist Curing Duration on
Modulus of Elasticity of Concrete at W/C = 0.33 ........ *****185




xvii








10.5 Influence of Aggregate Type and Moist Curing Duration on
Modulus of Elasticity of Concrete at W/C = 0.45 ....... ******186

10.6 Influence of Aggregate Type and Moist Curing Duration on
Modulus of Elasticity of Concrete at W/C = 0.53 ............. 187

11.1 Influence of Aggregate Type and Moist Curing Duration on
Coefficient of Expansion of Water-Saturated Concrete at
W/C = 0.33 .................................................. 203

11.2 Influence of Aggregate Type and Moist Curing Duration on
Coefficient of Expansion of Water-Saturated Concrete at
W/C = 0.45 .................................................. 204

11.3 Influence of Aggregate Type and Moist Curing Duration on
Coefficient of Expansion of Water-Saturated Concrete at
W/C = 0.53 .................................................. 205

11.4 Influence of Aggregate Type and Moist Curing Duration on
Coefficient of Expansion of Oven-Dried Concrete at W/C


11.5 Influence of Aggregate Type and Moist Curing Duration on
Coefficient of Expansion of Oven-Dried Concrete at W/C


11.6 Influence of Aggregate Type and Moist-Curing Duration on
Coefficient of Expansion of Oven-Dried Concrete at W/C



12.1 Influence of Aggregate Type and Moist-Curing Duration
on the Coefficient of Moisture Expansion of Concrete at
W/C = 0.33 .................................................. 22""

12.2 Influence of Aggregate Type and Moist-Curing Duration
on the Coefficient of Moisture Expansion of Concrete at
W/C = 0.45 .................................................. 226

12.3 Influence of Aggregate Type and Moist-Curing Duration
on the Coefficient of Moisture Expansion of Concrete at
W/C = 0.53 .................................................. 227

13.1 Mean Compressive Strength of In-Service Concrete
Pavement .......................

13.2 Mean Splitting Tensile Strength of In-Service Concrete
Pavement ...................................... ......248

13.3 Mean Modulus of Elasticity of In-Service Concrete
Pavement ........... *******o ...

13.4 Mean Water-Saturated Coefficient of Linear Thermal Expansion
of In-Service Concrete


xviii








13.5 Mean Oven-Dried Coefficient of Linear Thermal Expansion of
In-Service Concrete Pavement ....9................. ... ........ .251

13.6 Mean Coefficient of Moisture Expansion of In-Service
Concrete Pavement ........................................... 252

14.1 Plot of Splitting Tensile Strength Versus Compressive


14.2 Plot of Flexural Strength Versus Compressive Strength.....262

14.3 Relationship Between Elastic Modulus and Compressive


14.4 Relationship Between Splitting Tensile Strength and
Flexural Strength ......... ......99

15.1 Curling of Concrete Pavement Due to Temperature Differential [39] ................................27

15.2 Effect of Concrete Modulus on Maxinum Stresses Caused by a
22-Kip Axle Load and a Temperature Differential of +200F
[40] .............99.. ................. 8

15.3 Computed Maximum Longitudinal Stress Using FEACONS IV


15.4 Combinations of Modulus of Elasticity and Coefficient of
Thermal Expansion of Concrete to Produce Fixed Maximum


























xix














Abstract of Dissertation Presented to the Graduate School of the University of Florida in Partial Fulfillment of the
Requirements for the Degree of Doctor of Philosophy


COEFFICIENT OF THERMAL AND MOISTURE EXPANSION OF CONCRETE USED IN FLORIDA


By


Gabriel D. Alungbe


December 1939


Chairman: Dr. Mang Tia
Cochairman: Dr. David Bloomquist Major Department: Civil Engineering


A research study was conducted using laboratory-batched and inservice concrete specimens to determine the coefficient of linear thernal and moisture expansion of concrete used in Florida at temperatures ranging from 77 to 140'F (25 to 60'C).

Twenty-four concrete mixtures were prepared with three types of aggregates, namely Brooksville limestone, dense limestone, and river gravel. The former two are porous Florida aggregates while the latter is a nonporous aggregate obtained from Alabama. A type II Portland cement was used at a content of 508 Ib/cy (W/C = 0.53), 564 lb/cy (W/C =

0.45), and 752 Ib/cy (W/C = 0.33) for all the three types of aggregates and an additional 564 lb/cy (W/C = 0.53), 658 lb/cy (W/C = 0.45), and 658 ib/cy (W/C = 0.38) for Brooksville limestone. The laboratorybatched concrete specimens were moist-cured and tested at 28 and 90


xx








days. The in-service concrete core samples obtained from eleven project sites in Florida were prepared and tested as received.

Compressive strength, splitting tensile strength, modulus of rupture, and modulus of elasticity tests were performed on at least three specimens per batch per curing age of the laboratory concrete. The tests were also performed on concrete core samples from a few existing concrete pavements in Florida.

About two hundred 3" x 3" x 11 1/4" laboratory and 3" x 3" x 9" inservice concrete prisms were tested for thermal and moisture coefficient of expansion at water-saturated, partially-saturated, and oven-dried conditions. The coefficient of thermal expansion was affected by the aggregate types, curing age, and moisture conditions at measurement. The concretes made with Brooksville aggregate had the lowest coefficiel-,-of thermal expansion and those made with river gravel had the highest. The concrete made with dense limestone had ai intermediate coefficient of thermal expansion. The water-saturated laboratory concrete had lower coefficients of thermal expansion than the oven-dried concrete. However, the water-saturated in-service concrete had higher coefficients of thermal expansion than the oven-dried in-service concrete. The coeff'. cient of thermal expansion of oven-dried concrete specimens decreased with moist-cured age. No significant difference was observed in watersaturated concrete specimens. The coefficient of moisture expansion decreased with age.

Parameters of concrete mixes which affect the performance of concrete pavements were analyzed. A method for evaluation of concrete Inixtures for pavement construction was developed and presented.





xxi














CHAPTER I
INTRODUCTION


1.1 Background

In the past few years, great progress has been made in the analysis

and evaluation of concrete pavement response and performance through V cooperative efforts of the FDOT Materials Office and the University of Florida. Through field testing and analysis using the recently developed finite element program, FEACONS III, it has been determined that the two critical stress conditions occur when (1) a load is applied at the edge of a slab at midday when the slab is curled upward at the center, and (2) a load is applied near the slab corner at midnight or early morning when the slab is curled upward at the joints and edges. The critical stress conditions could be worsened by the presence of inplane stresses caused by overall thermal changes and constraints at the joints and edges. While the analytical tools for determining the critical stresses in a pavement system have been developed, the accuracy the computer results would depend on the accuracy of the input parameters. One area of uncertainty in the input parameters is the coefficient of linear thermal expansion of the concrete.

The coefficient of thermal expansion of concrete is listed in the literature as varying from 4 to 8 millionths per 'F (7.2 to 14.4 millionths per 'C), and is influenced primarily by the character of the aggregate and secondarily by the characteristics of the cement paste.





1




2


Data on Florida concrete are lacking. In the absence of actual data, a value of 6 millionths per 'F is usually assumed. This could result in an error of 30% in the coefficient of thermal expansion and errors of more than 100% in the computed stresses.

The effects of length change of concrete due to moisture variation are similar to those due to temperature variation. If there existed a moisture gradient within a concrete slab, the slab could warp in a similar manner as the slab would curl due to a temperature gradient. Data on the expansion and shrinkage due to moisture changes of Florida concrete are also lacking.

In view of the aforementioned reasons, this research project was started in order to obtain the needed data to be used in modelling and analysis of concrete pavement response and performance. In the course of this investigation, a need also arose in the determination of the coefficient of linear thermal expansion of structural concretes (Classes II, III & IV) used in Florida. The scope of the study was thus extended to cover the Florida Class II, III and IV concrete in addition to the pavement concrete (Class I).



1.2 Objectives of the Study

The main objectives of the study are

(1) To determine the coefficient of linear thermal expansion of

Florida Class I, II, III and IV concrete.

(2) To determine the linear shrinkage and expansion due to moisture

changes of Florida Class 1, 11, 111 and IV concrete.

(3) To determine the effects of mix parameters (such as aggregate

type, water-cement ratio, and cement content) and curing time





3



on the coefficient of thermal expansion, and the shrinkage and

expansion due to moisture changes of concrete.

(4) To determine the desirable concrete mixes to be used in concrete pavement construction.















CHAPTER 2
LITERATURE REVIEW


This chapter presents basic information on linear thermal expansion, definition of other thermal properties, a review of test methods previously used to determine linear thermal expansion of concrete, and the factors affecting the coefficient of linear thermal expansion of concrete.



2.1 Thermal Properties

The thermal properties of concrete which are of interest are coe4ficient of linear (and volumetric) expansion, thermal conductivity, thermal diffusitivity, and specific heat [1].

2.1.1 Linear Thermal Expansion

Almost all solids expand as the temperature rises and contract as the temperature falls. Concrete is an example of a solid that expandor contracts due to the change in temperature. The change in length ot a solid in response to the change in temperature is termed linear thermal expansion or contraction.

It is imperative to note that only uni-directional (or linear) expansion is considered even though we are fully aware of the area and volume expansion of solids due to change in temperature. The terms coefficient of linear thermal expansion and coefficient of thermal expansion are used interchangeably in this report.





4





5


According to Browne [2], the expansion of concrete due to increase

in temperature is uniform over the range from 32 to 140 OF (0 to 60 OC). Mitchell [3:2051 noted that the coefficient of thermal expansion is essentially constant over the range from 15 to 70 OF (-9.46 to 21.1 OC) in dry concrete" whereas a moist concrete "frequently shows a significant increase in thermal coefficients with increasing temperature." The length of a concrete specimen as a linear function of the temperature is illustrated in Figure 2.1.

Let us consider a rectangular piece of concrete having a length, L, at temperature, T, (see Figure 2.2). If the temperature is increased from T, to T2, the concrete will expand from L, to L2Linear expansion is the name given to the change in length. The length change can be expressed as

AL = L2 Ll
= aL 1 (T 2 T 1)

= aLl AT Eq. 2.1

where

AL = change in the length

L, = original length at T,

L2 = final length at T2

T, = original temperature

T2 = final temperature

AT = change in temperature

a = coefficient of linear thermal expansion

It can be seen from Equation 2.1 that the changing length is proportional to both the original length, L, and the change in temperature,





6


















E
N
G
T H Ll AT







T TZ,

TEMPERATURE




Figure 2.1 Uniform Expansion of Concrete





7






























AL

LZ





Figure 2.2 Linear Expansion of So6d





8


AT. The constant of proportionality is the coefficient of linear thermal expansion.

A positive change in length will increase the final length and conversely a negative change will result in the final length being shorter than the original. That is, the change in length can be additive or subtractive. Most engineering materials such as concrete can have a substantial change in length.

The coefficient of linear thermal expansion of concrete, denoted

by a, is the change in the unit length per degree change in temperature. It is expressed in terms of millionths per degree centigrade (x 10- 6/00 or millionths per degree Fahrenheit (x 10- 6 /*F) or percent.

The coefficient of linear thermal expansion consists of the true thermal expansion and the apparent thermal expansion [3, 41. The true or actual thermal expansion depends on the Kinetic molecular movements. Materials are composed of molecules which are in constant motion caused by forces of intermolecular attraction and repulsion. As the temperature increases, the molecular movement is also increased resulting in an expansion of a material. The expansion caused by molecular movement is constant.

The apparent thermal expansion is caused by "adsorptive mass attraction forces and capillary stresses" [5:67]. It is also termed 11swelling pressure" [4:493]. This type of expansion occurs in the cement paste region of the concrete. About 25% to 40% of the total volume of concrete is made up of cement paste [6]. The cement paste is hygroscopic. In the presence of free (evaporable) water, adsorptive and capillary forces are developed. The magnitude of the forces depends on





9


the change in temperature. As the temperature increases, the surface tension of the water and the capillary tension are reduced. Swelling pressure, which Dettling [5:17] defined as the "outer pressure needed to prevent swelling when a non-water-saturated gel has access to free water," is lost enabling the gel to withdraw water from the capillaries until equilibrium is once more attained. The cement paste swells when the cement gel gains water and shrinks when water is lost. Therefore, as the temperature rises at constant water content, the solid phase swells (apparent thermal expansion) in addition to the actual or true thermal expansion [7]. Moisture content, capillary structure of hardened cement paste, and quantity and expansion properties of cement gels are some factors that affect the magnitude of the apparent thermal expansion. According to Meyers [81, the apparent thermal coefficient of neat hardened cement paste is at minimum when completely water-saturated, a condition when all pores and capillaries are filled with water (100% saturated) and when all the evaporable water is removed, i.e., "bone dry" (0% evaporable water). Powers and Brownyard [71 attributed the condition to the existence of equality between vapor pressure of capillary water and saturation pressure of water at the existing temperature. A maximum value for the apparent thermal expansion of hardened cement paste and capillary forces is reached at a moisture content of about 70% of saturation [8]. Apparently capillary tension increases as water is lost from a water-saturated (100% saturation) specimen and also when moisture content is increased in a dry (0% moisture content) specimen.





10



The coefficient of volumetric thermal expansion is the ratio of the change of volume per unit volume per degree of temperature change. Volume change is expressed as Vt= Vo,(1 + at)

where

Vt = final volume at t temperature change

V0 = initial volume

a = coefficient of volumetric thermal expansion.

The coefficient of volumetric thermal expansion for an isotropic material is equal to three times the coefficient of linear thermal expansion; i.e.,

=3ai

2.1.2 Thermal Conductivity

It is the rate of heat flow, by conduction, through a body of unit thickness and unit area for a unit temperature difference between two surfaces. Thermal conductivity is expressed as


K (t9, tj) aT
Q= da
where

Q = heat conducted, cal gm/crr-sec-deg C

K = specific heat conductivity, calories

ttl= temperature difference, deg C

a = cross sectional area, cm2

d = thickness, cm

T = elapsed time, sec.








2.1.3 Thermal Diffusivity

It is defined as the thermal conductivity of a substance divided by the product of its density and specific heat, that is, a = k
Cp
where

a = thermal diffusivity (diffusion constant), m 2 Ar or ft 2 Ar

k = thermal conductivity

C = specific heat

p = density

It represents the rate at which a body with nonuniform temperature approaches equilibrium. According to Fintel [91, the diffusivity of concrete increases with an increase in aggregate content or decrease in water-cement ratio, an6 it decreases with an increase in temperature of the concrete.

2.1.4 Specific Heat or Thermal Capacity

Specific heat represents the amount of heat required to raise the temperature of a unit mass of homogeneous material by one degree. It is expressed as follows: S = m (t H -t

where 2 1

S = specific heat

H = quantity of heat added

m = weight of material

t 2- ti = temperature change in degrees





12


2.2 Test Methods

The absence of a standard method for determining the coefficient of linear thermal expansion of concrete has resulted in a situation where methods used by researchers are "almost as numerous as the number of laboratories" [3:209].

Berwanger and Sarkar [10] studied the effect of temperature and age

on thermal expansion and modulus of elasticity of concrete in the Civil Engineering Department at the University of Ottawa, Canada. Thirty-live

3 x 4 x 12-inch concrete prisms were cured both saturated and air-dried in the laboratory and tested at 7, 28, 84 days and at one year for coefficient of linear thermal expansion under short-term steady state temperatures ranging from -100 to 150 OF (-73 to 66 OC). Materials used. included Type I Portland cement, fine aggregates having a fineness modulus of 2.7 and contained 35% quartz, 29% carbonates, 23% feldspar, and 13% of amphibole, garnet, magnetite, mica and pyroxene. The coarse aggregate maximum size was 3/4 inch and consisted of 65% limestone, 25% feldspar, 5% quartz, and 3% mica. The water-cement ratios used ranged from 0.43 to 0.71. The strength of the concrete at 28 days varied between 4800 and 6340 psi. Optical extensometer telescope was used to measure the change in length of the concrete prisms. Transducers such as Direct Current Displacement Transformers (DCDT) were used to measure the deformations of some of the specimens and the aluminum deformation correction plates. Thermocouples were embedded in some of the wet- and dry-cured concrete prisms in order to measure the actual temperatures during testing. The following conclusions were arrived at

(1) At above freezing temperatures, the coefficient of linear thermal expansion increased with age for both dry- and wet-cured




13


specimens. However, for a given water-cement ratio, the drycured specimens increased more with age. Coefficient of linear

thermal expansion increased with decreased water-cement ratio.

(2) At below freezing temperatures, it is essentially the same as

for above freezing temperatures although the increase with age

was greater.

In his article entitled "Thermal Movement of Concrete," Browne [21 of Materials Research Laboratory at Taylor Woodrow Construction, United Kingdom, advocated the use of 6-inch diameter cylinders or 6 x 6 x 12inch prisms for the measurement of linear thermal expansion of concrete. The prisms, he stated, should be immersed in water for 28 days from casting and then heat cycled in a water bath. Thermal strains, he said, should be measured by a mechanical, electrical or optical strain measuring device with a known temperature correction factor.

The expansion and contraction of concrete and concrete roads was studied by Goldbeck and Jackson Ell] of former Office of Public Roads and Rural Engineering. The purpose of the laboratory study was to determine the change in length of concrete produced by the drying out and absorption of water. The concrete specimens used measured 8 in x 8 in x 5 ft high. Two one-half inch square steel bars were cast 50 inches apart into the concrete to serve as gage length. Materials used in preparation of specimens composed of normal (Type I) Portland cement, Potomac River sand, and crushed gneiss or gravel. The sand was coarse, and clean. All concrete mixtures were proportioned by weight and hand mixed at dry and wet consistencies. The quantity of water used for the dry mixtures was about 8.5% of the weight of dry materials. Between 10




14



and 12% was used for the wet mixtures. An instrument designed and constructed in their laboratory was used to take readings. It consisted of a micrometer head reading to 0.0001 inch mounted at the end of a steel yoke. The yoke contained two steel rods measuring five-sixteenths of an inch in diameter bolted to two end crosspieces, one holding the micrometer and the other a flat-ended steel pin. Readings were taken with the flat-ended pin held in contact with the lower conical point of the specimen and the micrometer screwed down to make contact with the upper conical point. Two readings were obtained. The readings were then averaged to obtain expansion or contraction along the center line. To detect change in the measuring instrument due to wearer misuse, readings were taken several times on a steel gage bar hung from the specimen. Readings were corrected for any change in temperature. It was observed that contraction took place almost immediately due to drying out of the water after molding. After 1 week of age, the specimen contracted approximately from 0.01 to 0.03 per cent, or from 0.0001 to 0.0003 inch per inch of length. The contraction, he reported, was caused exclusively by change in moisture. The finding from testing specimens kept in water for a period of about six months and allowed to dry in warm, dry air of the laboratory showed that concrete maintained almost constant expansion of approximately 0.0001 inch or 0.01 per cent while moist.

In a study conducted by Matsumoto [121 at the Engineering Experiment Station of the University of Illinois, the effect of moisture content upon the expansion and contraction of plain and reinforced concrete was investigated. The materials used were "universal" Portland cement, well graded sand from Attica, Indiana, as fine aggregate, and also




15


gravel from Attica as coarse aggregate. The specific gravity of the sand and gravel were 2.69 and 2.71, respectively. The concrete was hand mixed. The mix proportions were 1:1:2, 1:2:4, and 1:3:6. A batch of concrete was made for each concrete specimen. The specimens numbered thirty and measured 2 x 3 x 24 inches. Two steel plugs in the specimens formed a 20-inch gage line. Specimens were demolded one day after watching. Initial measurements of the length and weight were recorded and then stored in a damp room covered with double sheets of burlap which were kept wet. The instrument used in length measurement was a Berry Strain gage of 20-inch gage length with a steel bar immersed in water of known temperature as a standard. In an event of temperature change, measurements were corrected accordingly. Changes in weight were regarded as gains or losses in moisture content. The test results are shown in Table 2.1. It was observed that concrete expanded when wet and contracted when placed in dry air. Concrete with a richer mix absorbed more water and consequently expanded more than the lean mix.

Pence [131 of the School of Civil Engineering, Purdue University, studied the coefficient of linear thermal expansion of concrete between 1899 and 1901. The concrete specimen used measured 6 x 6 x 24 inches originally but later specimens were made cylindrical with 4-inche diameter and 36-inche length because of the great length of time required to heat the former. The method employed to determine the coefficient of linear thermal expansion was to subject the concrete specimen to a temperature change, and then to determine the increase in length, from which the coefficient of thermal expansion could be computed. A standard bar of steel or copper with known coefficient of linear thermal







16











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17



expansion and the concrete specimen were both subjected to changes in temperature. The principle of the "optical lever" was used to determine the difference of expansion of the concrete and steel or copper bars. The correction applied to the known coefficient of the metal bar was computed from the difference in length. The coefficient of linear thermal expansion of gravel concrete, broken stone concrete, and limestone bar was reported respectively as 5.4 x 10 6/OF (9.7 x 10 6/OC), 5.5 x 10-6/OF (9.9 X 10-6/OC), and 5.6 x 10-6/OF (10.1 X 10-6/OC).

Saemann and Washa r14] both professors of Mechanics, University of Wisconsin, Madison, conducted tests using mortars and concretes. The test temperatures varied between -70 and 450OF (-56.7 and 232 'C). Three concrete batches were made. The properties of the concrete mixes are presented in Table 2.2. The sand and gravel used were obtained locally in Madison, Wisconsin. The sand was calcareous and siliceous while the gravel was predominantly calcareous. Kenlite, an expanded shale, was obtained from Kentucky Light Aggregates, Inc. Type I Portland cement was used. The concrete specimens measured 2 x 2 x 11 inches and were cast with end studs. The specimens were moist-cured at normal room temperature for 14 days, then stored in air at 70'F (21.1%C) and 50% relative humidity for 13 days, and then held at test temperature for 24 hours prior to testing. During testing, the specimens were wrapped in paper and coated with paraffin to prevent change in moisture. Change in length accompanying a change in temperature from 70 to 00F (21.1 to

-17.8'C) was obtained and the coefficient of linear thermal expansion































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19


computed. A dial gage was used to measure change in length. The coefficient of linear thermal expansion for mixes 1, 2, and 3 were 4.4 x 10-6, 4.4 x 10-6, and 3.9 X 10-6/OF (7.9 X 10-6, 7.9 x 10-6, and 7.0 X 10-6/OC), respectively.

Cruz and Gillen [15] performed tests to determine the thermal expansion of Portland cement paste, mortar, and concrete at high temperatures at the Engineering Development Division of the Portland Cement Association. A blend of four commercially produced Type I Portland cements was used. Elgin, Illinois, sand was used in the two concrete batches investigated. It was composed of 60% carbonates (mostly dolomite) and 40% siliceous material by weight. Two types of coarse aggregate were gravel from Elgin, Illinois, and crushed dolomite rock from Elmhurst, Illinois. T:ie Elgin gravel was made up of 88% carbonates (mostly dolomite) and 12% siliceous material by weight and rock from Elmhurst was about 95% dolomite. The maximum size of coarse aggregate was 3/4 inch. The mix proportions by weight were 1:2.70:2.98 for Elgin concrete and 1:2.70:3.05 for Elgin/dolomite concrete. The W/C ratio by weight was 0.42 and 0.43 for Elgin and Elgin/dolomite concrete, respectively. The cement content of the two mixes was 568 pounds per cubic yard each. Both mixes had an air content of 4.5%. Three prisms measuring 5 x 6 x 6 inches were used per mix. The prisms were cast and cured for 7 days in a 100% relative humidity fog room at 23*C (73.4'F), dried for 20 days in an atmosphere of 50% relative humidity and 23%, and tested at an age of 28 to 30 days. Cores of 0.5-inch diameter and 3inch length were cut from the prisms and used for the test. The equipment used was a commercially manufactured dilatometer. It consisted of





20


a cylindrical electric furnace with the capability to heat specimens to 1600 *F (871*C). Length changes were measured by the Linear Variable Differential Transformer (LVDT). The temperature of the specimen was measured by a thermocouple. All the measurements were continuously recorded on an X-Y plotter. It was observed that Portland cement paste contracted while mortars and concretes expanded with increasing temperature. The average coefficient of linear thermal expansion for Elgin sand and gravel concrete was 7 x 10-6/OF (12.6 x 10-6/OC) and 7.9 x 10-6/OF (14.2 X 1rf6IOC) for dolomite rock.

In addition, optical lever has been used by Willis and De Reus [16] in determining the coefficient of thermal expansion of small concrete specimens. Extensometer frames have been used by the U.S. Bureau of Reclamation and described by Mitchell [17]. Optical interferometer method was used by Parsons and Johnson [18] of the National Bureau of Standards, Washington, D.C., to determine the thermal expansion of 137 specimens of aggregates at a temperature range of -4 to 140*F (-20 to 60 'C).

Bonnell and Harper [19] measured the coefficient of thermal expansion of different British aggregates and of concretes prepared from them with different cements, over the temperature range of 32 to 104*F (0 to 40%C). Six cylindrical test specimens were made from each mix. They were cured in one of the two curing conditions namely (1) air at 65% relative humidity (air storage) or (2) water. The change in length of the specimens was measured using an apparatus described by Bonnell and Watson [20]. Bonnell and Harper arrived at the following conclusions:

(1) Siliceous aggregates have the highest coefficients of thermal

expansion; limestones have the lowest coefficients while

igneous rocks have intermediate coefficients. The value for the




21


coefficient of thermal expansion for aggregates were found to

range f rom 2.1 to 6.5 x 10-6 per *F (3.8 to 11.7 x 10-6 per 'C) .

(2) The coefficient of thermal expansion of concrete depends

largely on the type of aggregate used in the mix. Concrete

made with siliceous aggregates have the highest thermal expansion, those with limestone have the lowest, and those with

igneous aggregates intermediate. The coefficient of concretes

ranges from 3.4 to 7.3 x 10-6 per *F (6.1 to 13.1 x 10-6 per

-C).

(3) The richer mixes tend to have slightly higher thermal expansion.

(4) The effect of age on the thermal expansion of concrete is only

minor.

(5) The method of curing and water content have only a small effect

on the thermal expansion.


2.3 Factors Affecting Coefficient of Thermal Expansion of Concrete

The coefficient of linear thermal expansion of concrete has been reported to be affected by the following factors [2, 21, 22]:

1. Type and amount of aggregate

2. Moisture content

3. Type and amount of cement

4. Concrete age

The first two factors are the principal factors affecting the coefficient of linear thermal expansion of concrete [2, 21].





22



2.3.1 Aggregate Type

In general, aggregates occupy about 60 to 80% of hardened concrete volume [2, 23, 6]. The coefficient of linear thermal expansion of concrete is largely dependent on the composition and quantity of the aggregates. Tables 2.3 and 2.4 show the reported average coefficients of linear thermal expansion of various rocks and minerals, respectively, within normal temperature ranges [5]. Quartz has the highest coefficient of linear thermal expansion of any common mineral. The coefficients of various types of rocks are directly related to their quartz content. Rocks such as quartzite, sandstone, and chert which are quartz-rich have the highest coefficients averaging about 6.7 x 19-6 per 'F (12 X 10-6 per OC). Those with little or no quartz, such as limestone and marble have the lowest coefficients averaging approximately

2.8 x 10-6 per OF (5 X 10-6 per OC). Igneous rocks such as granite and basalt which have medium quartz content have intermediate values. The coefficient of linear thermal expansion of composite rocks may be determined from the proportions of the major minerals and their average expansion [1].

The pertinent aggregate thermal characteristics were summarized by Emmanuel and Hulsey [23] as follows:

1. Generally, thermal coefficients of expansion for aggregates are

less than those for cement pastes.

2. Moisture content has little effect on the variability of the

average coefficient for aggregates.

3. Siliceous rocks have the highest coefficient, carbonate rocks

the lowest, and igneous rocks usually have intermediate values.





23


Table 2.3 Reported Coefficients of Linear Thermal Expansion of Various Rocks [5].


Average coefficient of
linear thermal expansion

Temp. 10-6/OC
range
Type of Rock 0C Limit values Average value

Quartzite, silica shale, ...60 11.0...12.5 11.8
flint, kieselgur, geyserite
Sandstones with siliceous 0...60 10.5...12.0 11.8
binders0...60 10.5...12.0 11.8
binders
Other sandstones 0...60 10.0...12.5 11.0
Quartz sands and gravels 0...60 10.0...12.5 11.0

Clay shale 0...60 9.5...10.5 10.1
Mica shale 0...60 10.0...11.0 10.7
Phyllite
Chlorite- and Talc- shale 0...60 7.0... 8.0 7.5

Granite, Arkosene,
Quartz prophry, liparite 0...60 6.5... 8.5 7.4
Gneiss, Granulites

Syenites, feldspathic porphyry, trachyte
Diorites, porphyrite,
Andesite, phonolite 0...60 5.5... 8.0 6.5
Gabbros, diabase,
Basalt
Peridotites, pikrite,
Limburgit
Dense, crystalline, porous a)3.5... 6.0 4.5
or odlitic limestones, 0...30 b) to 11.0
lime sinter c)

a) pure Galcite a)4.0... 6.5 5.0
b) with Aragonite 30...60 b) to 11.5
c) with Admixtures c)

Marbles 0...30 4.0... 7.0 4.5
Marbles 30...60 6.0...10.0 6.5

Dolomites, Magnesites 0...60 7.0...10.0 8.5





24





Table 2.4 Reported Coefficients of Linear Thermal Expansion of
a Few More Important Rock Minerals [5].



Average coefficient
Type of Mineral on linear expansion
i0- 6/0C

Silica Group
Quartz, Chalcedony 11.5 to 12
Opal 6 to 7

Feldspar Group
Potassium feldspars
Orthoclase ) 6.5 to 7.5
Microline )
Sodium calcium feldspars
Albite (sodium feldspar) 5 to 6
Oligoclase ) Andesite )
Labrador ) 4 to 3
Bytownite
Anorthite (calcium feldspar) 2.5 to 3

Feldspathoids (ca. 4.5 to 7.5) 1)

Mica Group ca. 8 to 12

Augite and hornblende group ca. 6.5 to 7.5

Olvine group 6 to 9) 1)

Carbonates
Calcite 4.5 to 5
Aragonite 20.5


1) The values cannot be regarded as free from uncertainty, as they
have not been checked by measurements.




25


4. Similar types of rocks from different sources have coefficients

that correspond to their mineral compositions.

5. Limestone aggregates within a normal atmospheric temperature

range have an average coefficient of approximately 2.5 x

10-6/OF (4.5 X 10-6/OC).

2.3.2 Moisture Content

The moisture content or the degree of saturation has been reported as one of the principal factors affecting the coefficient of linear thermal expansion of concrete. Neville [4, 241 reported that the effect of the moisture content on the coefficient of linear thermal expansion applies only to the paste component because thermal expansion is affected by (1) true kinetic thermal expansion and (2) swelling pressure. The true kinetic thermal expansion of a specimen is defined mainly by the spatial arrangement of its molecules and by the type of the material, and is not revealed by its chemical composition alone [5]. Swelling pressure is caused by a decrease in the capillary tension of water held by the paste with an increase in temperature [4, 241. The variation of the coefficient of linear thermal expansion of cement paste is much greater than that of concrete [17].

Dry (0% saturation) concrete at a temperature range of 15 to 70*F (-9.4 to 21.1 *0 has an essentially constant coefficient of linear thermal expansion while moist or nearly saturated concrete shows a significant increase in coefficient with increase in temperature [3]. The coefficient of thermal expansion of partially saturated concrete is generally 1.1 X 10-6/OF (2 x 10-6/OC) greater than when saturated [2]. Browne [21 attributed the high partially saturated value




26



to the increasing absorption by the gel of the capillary-held water with increasing temperature.

Settling [5] is of the view that for rocks, the variation of degree of saturation has no effect on the value of the coefficient of linear thermal expansion of rocks but has some effects on that of concrete.

Settling [51 regarded linear thermal expansion of concrete as a very complex physical process. The total linear thermal expansion is made up of (1) the actual linear thermal expansion and (2) the apparent linear thermal expansion [5]. The actual linear thermal expansion is the true linear thermal expansion caused by Brownian molecular movements produced by a change in temperature. Its value is constant. The apparent linear thermal expansion is a swelling pressure caused by "adsorptive mass attraction forces and capillary stresses" [5:67]. The swelling and shrinkage occur in the cement gels region because of internal moisture movements caused by a change in the capillary forces produced by variation in temperature [51. A completely dry or fully water saturated specimen has no apparent linear thermal expansion. Hence maximum apparent thermal expansion occurs when the specimen is partially saturated. The value of apparent thermal expansion is variable since it depends on age and degree of saturation. Aging of cement gels with time will reduce apparent thermal expansion.

Orchard [251 pointed out that the coefficient of linear thermal expansion is not affected by drying wet-cured concrete specimens.

2.3.3 Type and Amount of Cement

The type of cement does not greatly affect the coefficient of linear thermal expansion of concrete, as reported by Orchard E25]. During the early age of concrete, Meyers [261 observed that the value of the




27



coefficient is dependent on the quantity of tricalcium silicate (C3S) in the cement. He observed that cement with a high amount of tricalcium silicate compound had a high coefficient and those with low tricalcium silicate had a low volume change with temperature variation. With time, cements with a low amount of tricalcium silicate appeared to have a coefficient in the same range as those with high tricalcium silicate [261.

The coefficient of linear thermal expansion was reported to increase with an increase in the cement content of the concrete mix [261.

2.3.4 Concrete Age

Aging of saturated specimens tends to reduce the coefficient of

linear thermal expansion because of increased crystallization of the gel structure [2]. Neville [4, 241 attributed the increase in the amount of crystalline material in hardened paste to a reduction in the potential swelling pressure.

Orchard [251 pointed out that the time of wet-curing (i.e. in

water) has little effect on the coefficient of thermal expansion, while the time of dry-curing (i.e. in air) has little effect up to 3 months and tends to reduce the coefficient of thermal expansion slightly between 3 months and 1 year.

Matsumoto [12] found that the coefficient of expansion of mortar and concrete for different proportions and ages is practically the same as far as the same materials are used in all mixtures.

2.3.5 Other Factors

2.3.5.1 Curing condition. The coefficient of linear thermal expansion of concrete was reported to be slightly higher when cured





28


under dry conditions than wet conditions. Orchard [251 warned that the evidence was a little conflicting.

2.3.5.2 Heating/Cooling According to Dettling [51, the coefficient of linear thermal expansion is higher during cooling than during heating. He reasoned that increased expansion during cooling is possible only when there is no plastic deformations and loosening of structure.

Mitchell [17] and other investigators reported that the value of

the coefficient for aggregate obtained by going from low to high temperature is frequently slightly higher than starting from high to low temperature

2.3.5.3 Air voids. The coefficient of linear thermal expansion. of concrete was reported not to be affected by the presence of air voids [5, 241.

2.3.5.4 Size of test specimens. The determination of the coefficient of linear thermal expansion involves the measurement of very small changes in length. The accuracy and precision of the determination were reported to be greater for the longer specimens [271.

2.3.5.5 Type of storage liquid. The type of liquid used to store test specimens can affect the value of coefficient of linear thermal expansion. Meyers [26] noted that storage of test specimens at constant temperature in kerosene or glycerol does not cause the specimens to expand or contract as storage in water does. He reasoned that kerosene or glycerol does not become an integral part of the cement gel structure as water does.




29


2.3.5.6 -Freezing temperature. Settling [51 warned against the use of temperature range that includes 32 *F (O*C) to determine the coefficient of linear thermal expansion because freezing of pore water will cause volume change rendering the results inaccurate.


2.4 Effects of Thermal Expansion on Pavements

The property of concrete to contract and expand due to temperature and moisture variation is of tremendous importance to the engineers who design concrete structures. This dimensional instability influences the ability of concrete structures to provide maintenance-free service condition. Expansion and contraction affect concrete pavements in two ways. First, the existence of temperature and moisture differential between the top and bottom surfaces of the concrete pavement causes it to curl and warp, respectively E28]. Warping is counteracted by the weight of the slab [29]. Secondly, the expansion and contraction due to uniform temperature change in the entire cross section of the concrete pavement will result in the development of forces of friction between the pavement and the subgrade [29]. In addition to tensile stresses caused by wheel loads, a temperature drop also causes tensile stresses in concrete pavements. Conversely, a rise in temperature will produce compressive stresses. According to Bergstrom [29], the presence of compressive stresses in the boundary surface of pavement and subgrade can lead to blow-up unless the expansion joints are spaced not far apart.














CHAPTER 3
DEVELOPMENT OF A LABORATORY TESTING PROCEDURE FOR MEASURING LENGTH CHANGE OF CONCRETE This chapter describes the development of laboratory testing procedure used to measure the change in length of concrete specimens in this research project.



3.1 Introduction

There are many different methods for measuring the thermal expansion of solids. The methods may be classified as mechanical, electrical, optical, and X-ray. Examples of a mechanical method are dial gages and micrometer screws. Transducers, gages, tape transmitters are examples of electrical methods. Optical method examples are mirror arrangement, measurement microscope, and interference. The choice of the method to use depends on several factors including

1. Degree of accuracy and sensitivity

2. Automated or manual procedure

3. Properties of the material

4. Quantity of the material to be measured

5. Temperature range of the measurement

6. Type of information needed

7. Economy

All the methods used to measure change in length can be categorized as either relative or absolute [301. A method is termed relative when the expansion of the material being determined is measured relative to



30




31



the expansion of another material. When the expansion of the material being investigated is measured directly, the method is known as absolute.

A dial gage was selected to be used in the investigation. The selection of the dial gage method was influenced largely by the expediency, availability of equipment, size and quantity of the test specimens, and suitable experimental procedure. The method was found to be adequate for the investigation after preliminary experiments using the dial gage*


3.2 Test Equipment

The equipment used to conduct change in length measurements comprises essentially of a length comparator, water tank, and forced draft oven.

3.2.1 Length Comparator

The length comparator (see Figure 3.1) used was manufactured by the Humboldt Manufacturing Company, Norridge, Chicago, Illinois. It consists of a sensitive dial micrometer mounted on a sturdy upright support that is attached to a solid triangular base. The dial micrometer is graduated to read to 0.0001 inch. The range of the scale is 0.4000 inch. The dial has one large and two small count hands with needle pointers. The scale may be rotated to set for zero at any indication of the large needle pointer where it can then be locked by a set screw. The two smaller count hands with needle pointers on the face of the large dial show the number of revolutions of the larger pointer. One of the count hands shows the reading in 0.010 inch and the other hand shows it in 0.100 inch.





32
















































Figure 3.1 Length Comparator





33


There are two anvils fitted with collars and shaped to meet the

measuring studs cast into the ends of the test concrete bars. As supplied by the manufacturer, one of the anvils is movable whereas the other is stationary. The movable anvil is attached to the end of the indicator spindle while the stationary anvil is attached to the base with a threaded fastener through the base and a hex lock nut. The original threaded fastener was replaced with a longer one to facilitate adjustment to various heights. This was necessary because the specimens obtained from in-service concrete pavements are approximately 9 inches while the laboratory specimens are 11.25 inches long.

3.2.2 Water Tank

A water tank which was to be used to saturate and condition the concrete specimens to specified test temperatures was constructed for this study.

The water tank is rectangular in shape measuring 4 feet long by 2 feet wide by 1 foot high (see Figure 3.2). It was fabricated in the laboratory from 0.125 inch steel.

The tank was fitted with a heating element, thermometer, thermostat, and a pump. The eating element is used to heat the water to the desired temperature. The water temperature is read from the thermometer while the thermostat is used to control the water temperature. The pump circulates the water in the tank. This is necessary to keep the temperature of the water uniform all over the tank.

The interior of the tank was cleaned and smoothened with sandpaper. It was sprayed with sevPral coats of rust retardant and painted white. Two small hollow rectangular pieces of rods were glued to the





34 41
































Figure 3.2 Water Tank





35


bottom of the tank for the specimens to be placed on. This helps to circulate the heated water to all surfaces of the specimens.

The exterior of the tank was insulated using Tuff-R Insulating

Sheathing manufactured by the Celotex Corporation. It is a semi-rigid polyisocyanurate foam board insulation with a reinforced aluminum foil facer on one side and a solid aluminum foil facer on the other side. The nominal board thickness is 0.75 inch. The R-value, resistance to heat flow, at 75*F (23.9 'C) mean temperature aged over five years is

5.4.

3.2.3 Forced Draft Oven

A standard laboratory oven with approximately 2 cubic feet capacity was modified in the laboratory to enable flow of warm air through the oven. The modification was done by the provision of a large inlet port on one side of the oven and a small exit port on the top of the oven. A flexible aluminum duct was used to connect the two ports. A 375 cfm air booster was installed over the inlet port on the outside of the oven and connected to the duct line (see Figure 3.3.). A thermostat and sensor were also installed to control the temperature of the oven. A small hole was made on the side of the oven so that a thermometer could be inserted to check the temperature inside the oven.

3.2.4 Specimen Molds

A one compartment mold with inside dimension of 3 inches wide by 11.25 inches long was used to cast the test specimens. A total of ten molds were used per batch. The thickness of the steel mold is 0.5 inch. Two 0.375 inch thick, 3 inches square steel end plates with a hole at their centers were used to hold the contact points in place. Figure 3.4 shows a picture of the mold.






36























































4 # LL-





37














































Figure 3.4 Specimen Mold





38



3.3 Test Specimens

Specimens used were either concrete bars batched in the laboratory or bars sawed from cores obtained from selected in-service concrete pavements. Coring of samples was done by the Florida Department of Transportation district crew and coordinated by the Materials Office, Gainesville. The core samples were delivered to the Civil Engineering Department for further preparation to the desired shape. The identified and rough dressed cylindrical cores measured approximately 6 inches idiameter by 9 inches long. The samples were machined in the laboratory to rectangular cross sections measuring approximately 3 inches wide by 3 inches thick by 9 inches long. Steel saw blades were used to cut the core samples to the desired dimension.

A hole was drilled on each of the two ends in the long direction. One end of the contact point was dipped in epoxy and firmly inserted into the hole. It was then left to harden. The amount of epoxy used is so small that it should not affect the result.

The laboratory specimens measured 3 inches wide by 3 inches thick by 11.25 inches long. The specimens were obtained from concrete batches with each batch varying from others in terms of W/C ratio, type of coarse aggregate used, and cement content. Figure 3.5 shows a picture of a concrete specimen with embedded thermocouples.



3.4 Test Procedures

3.4.1 Measurement of Lengt Change

Prior to measuring length changes of the specimens, a high and low reading for the standard invar reference bar was obtained. Another high





39
















































L





40



and low reference bar reading was taken at the conclusion of measurements at a particular temperature. This was done because the room temperature might not be constant at the location of the apparatus. This measurement is necessary in order to adjust for the change in length of the reference bar. The following formula was used to correct length readings of the reference bar, if necessary, taken at temperatures other than an arbitrary standard temperature: Lstd temp. Lx (Tx Std.temp.) Gca Eq. 3.1

where

Lstdtemp. corrected length reading of the reference bar,

Lx = length reading of the reference bar taken at temperature 9

G = gage length, and

a = coefficient of linear thermal expansion of the reference bar material.

The coefficient of linear thermal expansion of invar is 1.6 x 10-6/OF (0.9 x 10%6/OC) [31] and stainless steel value range from 5.5 to

9.6 X 10-6/OF (9.9 to 17.3 x 10-6/OC) [32]. The reference bar for the laboratory specimens is an invar rod while that of field specimens is

stainless steel.

The correction factor for a V0F (2.8'C) variation in temperature is

0.000093 and 0.00026 for invar and stainless steel, respectively.

Specimens were initially conditioned to the desired temperature either in the oven or water tank for about 24 hours. The reason for this length of time is to make sure that the specimens actually attain





41



the desired temperature. As the project progressed, specimen temperature was measured with thermocouples embedded at the surface and middepth (Figure 3.5). It was apparent from thermocouple readings that the desired temperature can be attained within 3 hours. Therefore, conditioning of specimens for 24 hours was abandoned. Readings were taken after at least 6 hours of conditioning.

A specimen was brought to the instrument with the dial indicator retracted. It was carefully positioned in the lower anvil and the indicator released very slowly and carefully to make contact with the upper anvil. The specimen was then rotated slowly while measurement of the length was read aloud by one person and recorded by another on each of the four sides. The use of two people to read and record the change in length of the specimens was necessary to prevent the specimens from cooling before readings were completed. At later readings, the use of a second person was abandoned as a cassette recorder was used instead. The mean of the four readings was used as the length reading for that cycle. It was found, as discussed in the next section, that using two cycles of reading was sufficient for the precision required for this study. Consequently, two cycles of readings were used. The direction of the rotation of the specimen in the length comparator for cycle 1 was opposite to that used for cycle 2. Two opposite directions were used to reduce the effects of the direction of rotation on the results. The specimens were placed in the length comparator with the same end pointed up each time a length measurement was made.

3.4.2 Determination of Degree of Saturation of Test Specimens.

The volume of permeable pore space or voids in the test specimen was determined in accordance with ASTM C 642-82 with minor modification





42



to procedure 5.3. Since we are interested in knowing the moisture content of the specimen at the time of the test, the specimen was not allowed to "cool by natural loss of heat for not less than 14 hours to a final temperature of 68 to 770F (20 to 250C)" as required under the aforementioned procedure. Therefore, the saturated weight after boiling was obtained by weighing the surface-dried specimen after obtaining the change in length reading at 140'F (600C).

The degree of saturation of watersaturated specimen was determinc as follows:

Wt. of oven-dried specimen in air = A

Wt. of surface-dry specimen in air after immersion =B

Wt. of surface-dry specimen in air after immersion & boiling = C

Wt. of specimen in water after immersion & boiling Since

Voids (C C Ag x 0
Vw
Degree of saturation V ~ x 100



Ywv


Therefore,

Degree of Saturation C -A x 100

where

Y = unit weight of water,
V v = volume of voids

=volume of specimen x Voids(%)





43



3.4.2.1 Calculation of coefficient of linear thermal expansion The coefficient of linear thermal expansion, a of each of the samples was computed from the following equation: (L 2 Lj)/Lj Eq. 3.1
a = (T 2 T 1)


where

coefficient of linear thermal expansion,

L, = original length,

L2 = final length,

T, = original temperature, and

T2 = final temperature

3.4.3 Evaluation of the Test Method

A preliminary study was conducted to determine the effectiveness of the test procedure. First, the variability of the length readings from cycle to cycle was determined for various environmental conditions. Then, the number of cycles of readings was determined based on the variability of the data.

Table 3.1 displays the typical readings for four different conditions, namely (1) oven-dry at room temperature, (2) oven-dry at 140 OF,

(3) saturated at room temperature, and (4) saturated at 140 OF. It can be noted that the variability of readings from cycle to cycle (as seen from the standard deviation, Sx) is higher when readings are taken at 140 OF. For all the conditions, the standard deviations are equal or less than 0.0001 inch, which is the sensitivity of the length comparator. This indicates that the method used for the measurement of the





44






Table 3.1 Typical Length Readings for Four Different Environmental Conditions.





OVEN-DRY OVEN-DRY SATURATED SATURATED
CYCLE SIDE 82.4 OF* 140 OF 81.5 OF 140 OF
(28 0C) (60 'C) (27.5 0C) (60 0C

A 0.21112** 0.19659 0.22194 0.18490
B 0.21110 0.19662 0.22194 0.18490
1 C 0.21109 0.19662 0.22193 0.18439
D 0.21109 0.19658 0.22192 0.18488

AVG. 0.2111000 0.1966000 0.2219330 0.1848925

A 0.21100 0.19654 0.22194 0.18509
B 0.21110 0.19656 0.22194 0.18500
2 C 0.21104 0.19656 0.22192 0.18503
D 0.21110 0.19655 0.22192 0.18504

AVG. 0.21106 0.1965530 0.2219300 0.1850400

MEAN 0.2110800 0.1965765 0.2219315 0.1849663
STD). DEV. 0.0000283 0.0000332 0.0000021 0.0001I1
STD. 0EV. of Mean 0.0000200 0.0000235 0.0000015 0.000073j
(if 2 cycles
are used)

NOTE: *Temperature of specimen at time of test.
**Length readings are relative and in units of inches.




45



length is fairly effective and its precision is limited only by the precision of the length comparator. Although it may be sufficient to use only one cycle of measurement, it is decided to use two cycles of measurement so that (1) the mean length measurement would be more reliable, and (2) the variability of the readings could be checked. Table 3.1 also displays the standard deviations of the mean length readings for two cycles. It can be seen that the standard deviations of the means are much less than 0.0001 inch.

The coefficient of linear thermal expansion, a of each of the samples was computed from the following equation:



a = (L 2 Lj)/LI Eq. 3.2
(T 2 TJT


where

coefficient of linear thermal expansion,

L, = original length,

L2 = final length,

T, = original temperature, and

T2 = final temperature

The relationship for the coefficient of linear thermal expansion expressed in degree Fahrenheit and Centigrade is


a/ OC = 1. 8 d OF Eq. 3.3














CHAPTER 4
TESTING PROGRAM


This chapter presents the design of the experiment and the testing procedures used in the testing of laboratory and field specimens in this research study.



4.1 Laboratory Testing Program

4.1.1 Design of the Experiment

By the design of an experiment, we simply mean the plan of an experiment [33]. Experiments are planned or designed solely to provide the experimenter with maximum amount of information relevant to the problem being investigated at minimum cost. Also, analysis of data collected from designed experiment by statistical methods will yield valid and objective conclusions [331.

One of the main objectives of the laboratory study is to determine the effects of mix parameters (such as aggregate type, water-cement ratio, and cement content) and curing time on the coefficient of linear thermal expansion, and the shrinkage and expansion due to moisture changes of Florida Class 1, 11, 111, & IV concrete.

To achieve this objective, an incomplete factorial experiment incorporating the following variables was used in the study:

1. Three aggregate types--Brooksville limestone, a river gravel,

and a dense limestone (Calera aggregate).





46





47



2. Cement contents--508, 564, 658, and 752 lbs. per cubic yard.

3. Water/cement ratios--0.53, 0.45, 0.38, and 0.33.

4. Curing times--28 days and 3 months.

The concrete mixes for this study are displayed in Table 4.1. Two replicate batches per mix were made in order to have a reasonable statistical base. This amounts to a total of 24 batches. The order of making and testing the 24 batches was completely randomized.

A target slump of 3 inches was aimed for and was achieved by adding appropriate amounts of superplasticizer to the mixes. The exact proportioning of mix ingredients was determined from the trial batches. Initial designs of the trial batches were made using the COMIX computer program [34].

The tests peffornmed on the hardened concrete specimens at the various curing conditions were (1) flexural strength test using simple beam with third-point loading to determine the modulus of rupture which is the maximum stress at rupture, (2) compression test to determine the compressive strength and static modulus of elasticity, (3) length change due to temperature and moisture test, and (4) splitting tensile test to determine the splitting tensile strength (see Table 4.2).

The following tests was conducted on the fresh concrete for each batch of concrete:

1. Slump test

2. Air content test 3. Unit weight test.





48








Table 4.1 Mix Combinations for the Laboratory Study.




Aggregate Concrete Cement Content (lb. per cu. yd.)
Type Class 508 564 658 752

I
Brooksville wIc = .53 X X
II
Limestone w/c = .45 X X
III

w/c = .38 X

IV
w/c = .33 X

River I
Gravel w/c .53 X
II
w/c = .45 x

IV
w/c = .33 X

Dense I
Limestone w/c = 0.53 X
II
w/c =.45 X

IV
w/c = .33 X


Note: X Two replicate batches per cell





49















Table 4.2 Tests Performed on Each Batch of Concrete.






TEST

Flexural Compression Length Change Splitting Tensile
Curing Strength due to temperature Test (4" x 8"
(ASTM C78) (ASTM C469) and moisture cylinders'

28 days
Moist Room X X X X

3 months
Moist Room X X X X


Note: X Three replicate samples per cell.





50



4.1.2 Fabrication of Concrete Specimens

4.1.2.1 Mixing of concrete. The concrete batches were mixed in a stationary nontilting rotary type mixer with a maximum capacity of 25 cubic feet. The concretes was prepared in 13 cubic feet batches. The coarse aggregate and some mixing water was added into the mixer prior to starting rotation. A solution of air entrainment admixture was added to the mixing water. While the mixer was running, fine aggregate, cement, and about 80% of required water were added. After all the ingredient were in the mixer, the concrete was mixed for 3 minutes followed by a 3minute rest. The remaining water was added to the mixer followed by a 2-minute final mixing. A slump test was run to determine whether or not a target slump of 3 inches has been reached. If the slump was too low, a water reducing admixture, Mighty RD-1, was added to the mixture followed by another 2-minute mixing. Another slimp test was performed and the process as elucidated above repeated until the target slump was achieved. The amount of water reducing agent added to the concrete mix was small and so should not have any significant effect on the coefficient of linear thermal expansion.

4.1.2.2 Casting of concrete Specimens. After mixing was compile. the concrete was discharged into a large hopper through a rectangular opening on the side of the mixer. Concrete was extracted as needed from the hopper for fresh concrete tests, and for casting of beams, cylinders, and test specimens. The following tests were performed on the fresh concrete: slump test (ASTM C143-78), air content test (ASTM C17378), and unit weight test (ASTM C138-81) [351. The concrete mixture was then placed in 6" x 12" plastic cylinder molds, 4" x 8" plastic cylinder









molds, 6" x 6" x 30" steel beam molds, and 3" x 3" x 11-1/4" steel specimen molds. The molds were placed on two 20" x 20" syntron vibratory tables and vibrated while being filled with concrete mixture. Six 6" x 6" x 30" beam specimens, six 6" x 12" cylindrical specimens, six 4" x 8" cylindrical specimens, and ten 3" x 3" x 11-1/4" test specimens were cast for each batch of concrete. They were cured under a plastic sheet cover for about 20 to 24 hours before being demolded and cured in the moist room.

4.1.2.3 Curing of concrete specimens. The concrete specimens wer-, cured under two conditions, namely, 28-day and 90-day moist curing.

The moist room conforms with the ASTM requirements that the relative humidity be greater than 98% and the temperature be at 13 30F (22.8 1.6 0C).

4.1.3 Testing of Fresh Concrete

The tests performed on the fresh concrete are slump, air content, and unit weight.

4.1.3.1 Slump test. The slump test was performed in accordance with ASTM C143-78. Slump test is used to measure the consistency of concrete. The Florida Department of Transportation specified a slump~ range of 0 3.5 inches for vibrated placing of Class 1, 11, 111, and IV concrete. For non-vibrated placing, FOOT specified a slump range of 0

6 inches, 3 5 inches, and 7 9 inches for Class I, 11, and III concrete, respectively. No slump range is specified for non-vibrated Class IV concrete.

4.1.3.2 Air content test. Air content test was performed according to ASTM C173-78. The FOOT specifications require that all paving and




52



structural concrete should contain from 3 to 6 % of entrained air.

4.1.3.3 Unit weight test. The unit weight test was performed as

prescribed in ASTM C138-81. The test result is used to verify the computed density of the concrete mixes and for quality control.

4.1.4 Testing of Concrete Specimens

The tests performed on the hardened concrete specimens are flexural strength, compressive strength, splitting tensile strength, and length change due to temperature and moisture. The latter test has been described in Chapter 3. The description of the other tests follows.

4.1.4.1 Flexural strength test The test was performed in accordance with the ASTM C78-84 [351. Three 6" x 6" x 30" beam specimens were used per batch per curing condition.

If failure occurs within the middle third of the beam span length, the modulus of rupture was calculated as follows:



fr = Pt (4.1)
bd2
where

fr = flexural strength or modulus of rupture, psi,

P = maximum applied load, lbf,

= span length, inches,

b = average width of specimen, inches, d = average depth of specimen, inches.

The formula for calculating the modulus of rupture when failure occurs outside of the middle third of the span length by not greater than 5% of the span length is as follows:



fr = Pa (4.2)
bd2





53



where

a average distance between line of fracture and the nearest support measured on the tension surface of the beam, inches.

Test results were discarded if failure occurred outside the middle third of the span length by more than 5% of the span length.

The tensile strength of concrete is overestimated by 50 to 100 percent because the flexure formula assumes a linear stress-strain relationship in the concrete beam entire cross section [36]. Mehta [36] pointed out that flexural strength test is preferred for quality control of concrete used for highway and airport pavements where the concrete is loaded in bending.

4.1.4.2 Compressive strength test. Compressive strength tests were performed according to ASTM Standard Test Method C39-83b for Compressive Strength of Cylindrical Concrete Specimens. Three 6" x 12" cylindrical specimens per batch per curing condition were used for this test.

The moduli of elasticity of the concrete specimens were also determined at the conclusion of 28 and 90 days moist curing. A compressometer was used to measure the deformation of the cylindrical specimen as it was loaded in compression. The ASTM Standard Method C469-83 for Static Modulus of Elasticity and Poisson's Ratio of Concrete in Compression was followed during this test. The deformation at 40 percent of the average ultimate compressive strength of two concrete specimens was used to calculate the modulus of elasticity.

Modulus of elasticity was computed as follows:



E = Stress (4.3)
Tt Tral n





54





where

E = Modulus of elasticity, psi

Stress = Load/Area


= 'Load (lb) psi
T 7T


Strain = Actual deflection (in.)
Height of specimen (in.)


112 x Measured deflection (in.)
6 (in.)


Measured deflection (in.) in./in.
12


Essentially, modulus of elasticity is the measure of resistance of the concrete specimen to deformation. It is used to determine the stresses induced by strains caused by environti ental effects, to calculate the design stresses under a known load in simple elements, and to compute moments and deflections in complex structures [361.

Three methods are used to compute static modulus of elasticity

hence given rise to three moduli known as chord modulus, secant modulus, and tangent modulus.

The chord modulus is the slope of a line drawn from a point after correction for concavity to a point corresponding to 40 percent of the ultimate load. Mehta [36] recommends shifting the base line by 50 micro-strain (50 u in./in.) to correct for the slight concavity at the beginning of the stress-strain curve. This method yields a lower modulus [371.





55



The secant modulus is the slope of a line drawn from the origin to a point on the curve corresponding to a 40 percent stress of the failure load. This method was used to compute modulus of elasticity.

The secant modulus of elasticity is used in design [371.

The tangent modulus is the slope of a line drawn tangent to the stress-strain curve at any point on the curve.

4.1.4.3 Splitting tensile strength test. The splitting tensile strength tests were performed in accordance with ASTM Standard Method C496-71 for Splitting Tensile Strength of Cylindrical Concrete Specimens. Three 4" x 8" cylindrical specimens were used for this test.

The splitting tensile strength of the specimen was calculated as follows:


f = 2P (4.4)
t Tr Xd

where

ft = splitting tensile strength, psi

P = maximum applied load, lbf z = length of cylinder, inches

d = diameter of cylinder, inches



4.2 Study of In-Service Concrete Concrete samples from existing concrete pavements and structures in Florida were obtained to study the thermal and hygroscopic properties of the in-service concrete. Ten pavement (Class I concrete), one Class II, one Class III and one Class IV concrete projects were selected for this study. Ten core samples (6 inches diameter) were obtained from each of these thirteen projects. Of these ten samples, two were evaluated in





56



the splitting tensile strength test, two were evaluated for their elastic moduli and compressive strengths and the other six were sawed into 3-inch square prisms. Holes were drilled at the two ends of the prismatic samples and contact points were inserted into the holes and glued to the sample with epoxy. These prismatic bars were conditioned to various temperature and moisture conditions and the length changes were measured at these conditions using the procedure described in Chapter 3. The following temperature and moisture levels were used:

1. 77, 86, 104, 122, and 140 'F (25, 30, 40, 50, and 60'C) at ovet.

dry condition.

2. 77, 86, 104, 122, and 140 'F (25, 30, 40, 50, and 600C) at

saturated condition.

3. 77'F (25'C) at three different partially saturated conditions.

The conditioning procedure is similar to the laboratory specimen.














CHAPTER 5
MATERIALS


This chapter presents the properties of the Portland cements,

aggregates, and admixtures used in the preparation of laboratory test specimens of this project.


5.1 Cements

The cement used was a Type II Portland cement manufactured by General Portland, Inc., Tampa, Florida. The results of physical and chemical analyses on the cement was supplied by the manufacturer and are listed in Tables 5.1 and 5.2.



5.2 Aggregates

Three types of coarse aggregate were used. They are a porous limestone (Brooksville aggregate), a dense limestone (Calera aggregate) and a river gravel. One maximum aggregate size of 3/8 inch (#89) was used. Tests on these aggregates were performed for another research study by Tia et al. [38]. Test results from that study were used. The physical properties of the coarse aggregates are displayed in Table 5.3. The gradation charts for the Brooksville, river gravel, and Calera aggregates are shown in Figures 5.1 through 5.3, respectively.








57





53












Table 5.1 Results of Physical Tests on Cement Used [381.





TYPE Il
CEMENT

Fineness by 2/
Blaine air permeability test, cm /g3970 Soundness (autoclave expansion), % -0.01

Time of setting (Gilmore): Initial, hrs:mins 2:45
Final, hrs:mins 4:25

Compressive Strength: 1 Day, psi 1990
3 Days, psi 3040
7 Days, psi 4190

Air Entrainment, %9.1





59










Table 5.2 Results of Chemical Analyses on Cement Used [38].






CEMENT
TYPE II

Silicon Dioxide (Si02), % 21.6
Aluminum Oxide (A1203), % 4.5
Ferric Oxide (Fe203), % 4.1
Magnesium Oxide (MgO), % 0.6
Sulfur Trioxide (S03), % 2.9
Loss on Ignition, % 0.9
Insoluble Residue, % 0.17
Alkalis (%Na20+O.658K20), % 0.36
Tricalcium Silicate, % 54
Dicalcium Silicate, % 21
Tricalcium Aluminate, % 4.8
Tetracalcium Alumino Ferrite, % 12.6





60















Table 5.3 Physical Properties of Coarse Aggregates.






Coarse Aggregate River
Brooksville Calera Gray
Property #89 #89 #89

Bulk Specific Gravity 2.50 2.70 2.59
(SSD) (2.29)*

Absorption (%) 2.95 0.4 1.46
(5.34)*
Unit Weight (lb/ft3) 92.0 96.82 100.38
(86.42)*

* Batches 9-12








61











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64



The fine aggregate used for all mixtures was a fine sand from Goldhead, Florida. The gradation of this sand is depicted in Figures 5.4 and 5.5. The physical properties of this sand are as follows:

Bulk specific gravity (SSO) 2.52 for batches 1-19

2.43 for batches 20-24

Absorption 0.70% for batches 1-19

0.44% for batches 20-24

Fineness modulus 2.26 for batches 1-19

2.11 for batches 20-24



5.3 Admixtures

An admixture, Mighty RD-i, was used to adjust the slump of the fresh concrete to a target slump of 3 inches. This admixture meets

the requirements of ASIM C494 Type G and Type D, and is classified as a water-reducer and retarder.

A Darex air entrdiiiing admixture was used.



5.4 Epoxy

A Sikadur 32, Hi-Mod, 2-component (A & B), solvent-free moistureinsensitive structural epoxy adhesive was used to secure contact points to the field and some laboratory specimens.








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CHAPTER 6
EXPERIMENTAL DESIGNS OF THE LABORATORY STUDY


6.1 Introduction

One of the principal objectives of this study as stated in Chapter 2 is to determine the effects of mix parameters (aggregate type, watercement ratio, and cement content) and curing time on the coefficient linear thermal expansion of concrete. In addition, the effects of mix parameters and curing time on the compressive strength, splitting tensile strength, modulus of rupture and modulus of elasticity will be studied.

The mix parameters (main factors) and their interactions are displayed in Table 6.1.

Table 4.1 summarizes the mix combinations for the laboratory stuaj. Since the study involves more than one factor, a factorial experiment was used. A factorial experiment is referred to as complete if combination of all levels of each factor with all levels of every other factor exists. However, certain impractical factor level combinations (treatment combinations) were excluded from the study resulting in an incomplete factorial experiment. Statistical analysis and interpretation problems are created when some combinations are missing. In this study, a complete factorial experiment was precluded because of the specification requirement that a certain class of concrete must be made with a certain amount of cement and water-cement ratio. Treatment combinations





57





68







T able 6.1 Factors, Levels, and Interactions for the Partial
Factorial Experiment.




Main Factors Levels
1 2 3 4


Aggregate Type (A) BL RG DL

Cement Content -lb/cy 508 564 558 752
(C)

Curing Duration -days 28 90
(0)

Water-Cement Ratio 0.53 0.45 0.38 0.33
(E)





Two-Factor Interactions -Three-Factor Interactions
A xC A x C x
A x D A x C x E
A x E x xDx E
C x D C xE
D xE Four-Factor Interactions
A xC x Dx E


NOTE:
BL =Brooksville Limestone
RG = River Gravel
DL = Dense Limestone





69



beyond the code stipulated limits would produce a concrete mix unsuitable for construction use.

In order that we can effectively analyze the significance of the main effects and interactions, the partial factorial design as shown in Table 4.1 is treated as seven (7) small complete factorial experiments. These seven experimental designs are described in this chapter.



6.2 Design No. 1 The purpose of this design was to study the effects of aggregate

type, water-cement ratio, and curing duration on the dependent variables which are compressive strength, splitting tensile strength, modulus of rupture, modulus of elasticity, and the coefficient of linear thermal expansion of the laboratory study. This design disregards the difference in the cement content of the batches. The main factors and their levels under study are



Factor A: Aggregate type

Level 1. Brooksville limestone

Level 2. River gravel

Level 3. Dense limestone Factor D: Curing duration

Level 1. 28-day Level 2. 90-day

Factor E: Water-Cement ratio

Level 1. 0.53 Level 2. 0.45 Level 3. 0.33





70


Table 6.2 displays the experimental design. Each batch is replicated twice.



6.3 Design No. 2

At a fixed cement content of 508 lb. per cubic yard and watercement ratio of 0.53, the effects of aggregate type (3 levels) and curing duration (2 levels) on dependent variables such as compressive strength, splitting tensile strength, modulus of rupture, modulus of elasticity, and coefficient of linear thermal expansion are studied. The main factors and their levels are



Factor A: Aggregate type

Level 1. Brooksville limestone

Level 2. River gravel

Level 3. Dense limestone Factor D: Curing duration

Level 1. 28-day Level 2. 90-day


The experimental design is shown in Table 6.3. There are two replicate batches for each mix design.



6.4 Design No. 3

In this of experiment, the main factors are the same as in Design No. 2 with the exception that the fixed cement content and water-cement ratio are 564 lb/cu.yd. and 0.45, respectively. The design is presented in Table 6.4.





71










Table 6.2 Design for Test on Effects of Aggregate Type,
W/C Ratio at Variable Cement Content, and Curing
Duration (Design No. 1).



Ceme W/C 0.53 0.45 0.33
i' 508 Ib/cy 564 Ib/cy 752 ib/cy
rat28-day 90-day 28-day 90-day 28-day 90-day
Aggregate 8dy 9-a 8dy 9-a 8dy 9-a

Brooksville Limestone X X X X X X

River Gravel X X X X X X

Dense Limestone X X X X X X



X = Two replicate batches per cell.





72















Table 6.3 Design for test on effects of aggregate type and
curing duration at W/C of 0.53 and cement content
of 508 Ib/cy (Design No. 2).


Curing Duration 28- 90Aggregate Type Day Day

Brooksville x
Limestone

River Gravel Dense
Limestone


Note: X = Two replicate batches per cell.





73













Table 6.4 Design for test on effects of aggregate type and
curing duration at W/C of 0.45 and cement content
of 564 Ib/cy (Design No. 3).



Curing Duration 28- 90Aggregate Type Day Day

Brooksville
Limestone

River Gravel

Dense X X
Limestone


Note: X = Two replicate batches per cell.





74


6.5 Design No. 4 Design No. 4 is similar to Design No. 2 except that the fixed cement content and water-cement ratio are respectively, 752 lb/cu.yd. and

0.33. Table 6.5 shows the experimental design.



6.6 Design No. 5 In this design, the effects of the cement content and curing duration on the compressive strength, splitting tensile strength, modulus of rupture, modulus of elasticity, and coefficient of linear thermal expansion was studied at fixed water-cement ratio and aggregate type. The design is presented in Table 6.6. The factors and their levels are


Factor C: Cement content

Level 1. 508 lb/cu.yd.

Level 2. 564 lb/cu.yd. Factor D: Curing duration

Level 1. 28-day Level 2. 90-day



Each mix design was duplicated twice.



6.7 Design No. 6 This design is similar to that of No. 5 except for the difference that the water-cement ratio is fixed at 0.45. The design is given in Table 6.7.





75














Table 6.5 Design for test on effects of aggregate type and
curing duration at W/C of 0.33 and cement conte,
of 752 Ib/cy (Design No. 4).



Curing Duration 28- 90Aggregate Type Day Day

Brooksville x x
Limestone

River Gravel Dense
Limestone


Note: X = Two replicate batches per cell.






76














Table 6.6 Design for test on effects of cement content and
curing duration given W/G of 0.53 and Brooksville
limestone (Design No. 5).




Cement Curing 28- 90Content Duration Day Day
(ib/cy)

508 X X

564 X X




Note: X = Two replicate batches per cell.





77













Table 6.7 Design for test on effects of cement content and
curing duration given W/C of 0.45 and Brooksville
limestone (Design No. 6).


Cement Curing 28- 90Content Duration Day Day
(lb/cy)

564 X X

658 X X



Note: X = Two replicate batches per cell.




78


6.8 Design No. 7 Design No. 7 dealt with the effects of water-cement ratio and curing duration of Brooksville limestone at cement content of 658 lb/cu.yd. on the compressive strength, splitting tensile strength, modulus of ruptue, modulus of elasticity, and coefficient of linear thermal expansion. Table 6.8 displays the design. The main factors and their levels are

Factor D: Curing duration

Level 1. 28-day Level 2. 90-day

Factor E: Water-cement ratio

Level 1. 0.45 Level 2. 0.38


There are two replicate batches per mix design.





79
















Table 6.8 Design for Test on Effects of W/C Ratio and Curing
Duration Given Brooksville Limestone and Cement
Content of 658 ib/cy (Design No. 7).


Curing 28- 90W/C Duration Day Day

0.45 X X

0.38 X X




Note: X = Two replicate batches per cell.