Jan 15, 2015 - Freezing-Thawing and Wetting-Drying Conditions. Doctor of Philosophy ... AGGREGATE ON PROPERTIES OF PAVEMENT CONCRETE EXPOSED TO ...... Four different binder systems were used, and included the following: ..... that of normal weight aggregates typically ranges between 75 and 110 lb/ft. 3.
Graduate School Form 30 Updated 1/15/2015
PURDUE UNIVERSITY GRADUATE SCHOOL Thesis/Dissertation Acceptance
This is to certify that the thesis/dissertation prepared By Kho Pin Verian Entitled Influence of Air-Cooled Blast Furnace Slag (ACBFS) Coarse Aggregate on Properties of Pavement Concrete Exposed to Freezing-Thawing and Wetting-Drying Conditions
For the degree of Doctor of Philosophy
Is approved by the final examining committee: Jan Olek Chair
W. Jason Weiss John E. Haddock Terry W. West
To the best of my knowledge and as understood by the student in the Thesis/Dissertation Agreement, Publication Delay, and Certification Disclaimer (Graduate School Form 32), this thesis/dissertation adheres to the provisions of Purdue University’s “Policy of Integrity in Research” and the use of copyright material.
Approved by Major Professor(s): Jan Olek
Approved by: Rao S. Govindaraju Head of the Departmental Graduate Program
11/2/2015 Date
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INFLUENCE OF AIR-COOLED BLAST FURNACE SLAG (ACBFS) COARSE AGGREGATE ON PROPERTIES OF PAVEMENT CONCRETE EXPOSED TO FREEZING-THAWING AND WETTING-DRYING CONDITIONS
A Dissertation Submitted to the Faculty of Purdue University by Kho Pin Verian
In Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy
December 2015 Purdue University West Lafayette, Indiana
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And we know that in all things, God works for the good of those who love Him, who have been called according to His purpose. (Romans 8:28)
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ACKNOWLEDGEMENTS
My deep gratitude goes first to Professor Jan Olek, who patiently guided me through my graduate education and who shared the knowledge and wisdom of more than six years of the time I have spent at Purdue University. His personal generosity and humility became a role model for my personal life, which contributes to my growth in character as a person. His unwavering enthusiasm towards work has been a noble example for me and the other students. His kindness and lovely character have helped make my time at Purdue valuable. My appreciation also extends to Professor Jason Weiss, Professor John E. Haddock and Professor Terry West for serving as my advisory committee. Their valuable suggestions, guidance and help have further improved the quality of this study. I am personally grateful for having such outstanding professors in my committee. I gratefully acknowledge the financial support provided by Purdue University through the Joint Transportation Research Program (project SPR 3310). I would like to thank Jennifer R. Ricksy, Susan Bales, Dorothy J. Miller, Debra S. Burrow, Alan Holtman and Sharon Nemeth. I would like to extend my acknowledgements to Tommy Nantung, who served as the principal administrator of my research project. In addition, my appreciation goes to Solidia Technologies not only for the internship opportunities, but also for providing financial support during my last semester at Purdue. I would like to thank Parth Panchmatia, a friend who has helped me for going through many challenges at Purdue. To my friends and colleagues: Ali Behnood, Charles Chiu, Taehwan Kim, Chaitanya Paleti, Ina Ruggerio, Jitendra Jain, Eric Smith, Raikhan Tokpatayeva, Warda Ashraf, HyunGu Jeong, Juan Tabares and Belayneh Desta. Thank you for the sharing thoughts and insightful discussions. Thank you for making our office an enjoyable place to stay and work.
iv I would like to extend my appreciation to Kyle Johnson, Raymond Faber, Nick Callahan, Caleb Butler, Rama Chintapalli, Nancy Whiting and Frederick Chung. Thank you to Matt, Leonia and Erik Scott, George and Beverly Moore, Aaron Birk, Michael Barton, Faith Church and Christ Community Church bible study groups. Thank you for the love, prayer, support and guidance, especially for laughter and the time we spent together. In addition, I would like to thank Dr. Cecilia Lauw Giok Swan, my former advisor at Indonesia who encouraged me to pursue my higher education at Purdue University. To Santa Regina, thank you for the prayer and encouragement. Special thanks to mother who always keeps me in her prayers, and I will always be grateful to my father, sisters and brothers back at Indonesia for their love and support. Finally, I want to thank God for His faithfulness and grace. His love endures forever. I am grateful that my journey at Purdue was not an easy one, but it is worthwhile.
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TABLE OF CONTENTS
Page LIST OF TABLES .............................................................................................................. x LIST OF FIGURES .......................................................................................................... xv LIST OF ABBREVIATIONS ....................................................................................... xxxii ABSTRACT................................................................................................................. xxxiii CHAPTER 1. INTRODUCTION ....................................................................................... 1 1.1
Background .............................................................................................................. 2
1.2
Research Objectives and General Hypothesis ......................................................... 4
1.3
Scope of the Research .............................................................................................. 5
1.4
Organization of the Thesis ....................................................................................... 6
CHAPTER 2. LITERATURE REVIEW ............................................................................ 8 2.1
Introduction .............................................................................................................. 8
2.2.1
Properties of Air-Cooled Blast Furnace Slag ................................................... 8
2.2.2
Influence of Chemical Properties of Air-Cooled Blast Furnace Slag on Concrete ............................................................................................. 10
2.2.3
Influence of Mechanical Properties of Air-Cooled Blast Furnace Slag on Concrete ............................................................................................. 12
2.3
Slag Cement/Ground Granulated Blast Furnace Slag (GGBFS) ........................... 13
2.3.1
Hydration Products of Slag Cement ............................................................... 13
2.3.2
Properties of Concrete Containing Slag Cement ............................................ 14
2.4
2.3.2.1
Fresh Concrete Properties ...................................................................... 14
2.3.2.2
Strength Development ............................................................................ 14
2.3.2.3
Durability ............................................................................................... 15
Fly Ash ................................................................................................................... 16
vi Page 2.4.1
Pozzolanic Reaction of Fly Ash ..................................................................... 16
2.4.2
Properties of Concrete Containing Fly Ash .................................................... 16
2.5
The Effects of Deicers on Concrete Pavement ...................................................... 17
2.5.1
Physical Deterioration .................................................................................... 17
2.5.1.1
Hydraulic Pressure Theory ..................................................................... 18
2.5.1.2
Osmotic Pressure Theory ....................................................................... 18
2.5.1.3
Thermal Shock ........................................................................................ 18
2.5.1.4
Layer-by-layer Deterioration.................................................................. 18
2.5.1.5
Growth of the Salt Crystals .................................................................... 19
2.5.1.6
Super Cooling......................................................................................... 19
2.5.2
Chemical Deterioration................................................................................... 20
2.5.2.1
Effects of Calcium Chloride (CaCl2) on Concrete Properties ................ 20
2.5.2.2
Effects of Magnesium Chloride (MgCl2) on Concrete Properties ......... 21
2.5.2.3
Effects of Sodium Chloride (NaCl) on Concrete Properties .................. 21
CHAPTER 3. MATERIALS, MIXTURE COMPOSITIONS AND TEST PROCEDURES ...................................................................................................... 23 3.1
Concrete Making Materials ................................................................................... 23
3.1.1
Cement ............................................................................................................ 23
3.1.2
Fly Ash ........................................................................................................... 24
3.1.3
Slag Cement .................................................................................................... 25
3.1.4
Aggregates ...................................................................................................... 26
3.1.5
Deicing Materials ........................................................................................... 26
3.1.5.1
Sodium Chloride (NaCl) ........................................................................ 26
3.1.5.2
Magnesium Chloride (MgCl2)................................................................ 27
3.1.5.3
Calcium Chloride (CaCl2) ...................................................................... 27
3.2
Selection of Exposure Conditions.......................................................................... 27
3.3
Mixture Compositions ........................................................................................... 29
3.4
Mixing Procedure .................................................................................................. 31
3.5
Test Matrix ............................................................................................................. 33
vii Page 3.5.1
Aggregate Tests .............................................................................................. 34
3.5.1.1
Sieve Analysis ........................................................................................ 34
3.5.1.2
Specific Gravity, Absorption and Moisture Content.............................. 34
3.5.1.3
Los Angeles (L.A) Abrasion Test .......................................................... 35
3.5.1.4
Desorption .............................................................................................. 35
3.5.1.5
Leaching Behavior of Coarse Aggregate ............................................... 36
3.5.2
Fresh Concrete Testing ................................................................................... 37
3.5.2.1
Slump ..................................................................................................... 37
3.5.2.2
Determination of Air Content ................................................................ 37
3.5.2.3
Unit Weight ............................................................................................ 37
3.5.3
Hardened Concrete Testing ........................................................................... 37
3.5.3.1
Compressive Strength ............................................................................ 38
3.5.3.2
Flexural Strength .................................................................................... 38
3.5.3.3
Dynamic Modulus of Elasticity.............................................................. 39
3.5.3.4
Mass Changes of Specimen.................................................................... 40
3.5.3.5
Length Changes ...................................................................................... 40
3.5.3.6
Physical Changes in the Test Specimens ............................................... 41
3.5.3.7
Chloride Penetration Depth .................................................................... 41
3.5.3.8
Scanning Electron Microscopy .............................................................. 41
3.5.3.9
Determination of Leachable Ions ........................................................... 41
3.5.4
Pore Solution Analysis of Concrete Paste with Different Binder System ...... 42
CHAPTER 4. EXPERIMENTAL RESULTS AND ANALYSIS .................................... 43 4.1
Aggregate Test Results .......................................................................................... 43
4.1.1
Sieve Analysis, Absorption and Specific Gravity .......................................... 43
4.1.2
Los Angeles (L.A) Abrasion Test Results ...................................................... 45
4.1.3
Desorption Test Results .................................................................................. 46
4.1.4
Determination of Ions Leached from Coarse Aggregates and pH Measurements ................................................................................... 48
4.2
Concrete Test Results ............................................................................................ 51
viii Page 4.2.1
Fresh Concrete Test Results ........................................................................... 51
4.2.1.1
Slump Test Results ................................................................................. 51
4.2.1.2
Air Content and Unit Weight ................................................................. 53
4.2.2
Hardened Concrete Test Results..................................................................... 55
4.2.2.1
Compressive Strength Results................................................................ 55
4.2.2.2
Flexural Strength Results ....................................................................... 73
4.2.2.3
Relative Dynamic Modulus of Elasticity (RDME) ................................ 74
4.2.2.4
Changes in Relative Mass ...................................................................... 80
4.2.2.5
Length Change ....................................................................................... 85
4.2.3
Changes in the Physical Appearance of Specimens ....................................... 90
4.2.4
Chloride Ion Penetration Depth .................................................................... 102
4.2.5
Scanning Electron Microscopy (SEM) ......................................................... 107
4.2.6
Determination of Ions Leached from Different Concretes and the pH Measurements ................................................................................... 116
4.2.7
Pore Solution Analysis Results..................................................................... 118
CHAPTER 5. DISCUSSION AND SUMMARY .......................................................... 122 5.1
The Effect of Air-Cooled Blast Furnace Slag (ACBFS) Coarse Aggregate on Concrete Properties ....................................................................... 122
5.2
The Effect of Fly Ash as Partial Cement Replacement on Concrete Properties ............................................................................................................. 124
5.3
The Effect of Slag Cement as Partial Cement Replacement on Concrete Properties ............................................................................................................. 124
5.4
The Effect of Ternary Binder System (Fly Ash + Slag Cement + OPC) on Concrete Properties ......................................................................................... 125
5.5
The Effect of NaCl Deicer on Concrete Properties ............................................. 126
5.6
The Effect of MgCl2 Deicer on Concrete Properties ........................................... 126
5.7
The Effect of CaCl2 Deicer on Concrete Properties ............................................ 127
ix Page CHAPTER 6. CONCLUSIONS AND GENERAL RECOMMENDATION................. 128 6.1
Conclusions .......................................................................................................... 128
6.2
General Recommendation.................................................................................... 130
LIST OF REFERENCES ................................................................................................ 131 APPENDICES APPENDIX A – MATERIALS CERTIFICATE ........................................................... 139 APPENDIX B – TEST RESULTS ................................................................................. 142 APPENDIX C – SEM RESULTS .................................................................................. 184 VITA ............................................................................................................................... 204 PUBLICATIONS ............................................................................................................ 205
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LIST OF TABLES
Table
Page
Table 2-1. Typical composition of ACBFS [14]. ............................................................... 9 Table 3-1. Chemical composition of Type I portland cement. ......................................... 24 Table 3-2. Chemical and physical data of class C fly ash. ............................................... 25 Table 3-3. Chemical and physical data of slag cement (SC) used in the study. ............... 25 Table 3-4. Summary of exposure conditions used in previous deicing/anti-icing studies [12]..................................................................................................... 28 Table 3-5. Material proportions and w/cm for each mixture. ........................................... 30 Table 3-6. Test matrix used in the study. .......................................................................... 33 Table 3-7. proportions of pastes used in pore analysis study. .......................................... 42 Table 4-1. Specific gravity and absorption of aggregates used in the study..................... 44 Table 4-2. Specific gravity and absorption data for dolomite and ACBFS coarse aggregates used in statistical analysis................................................. 44 Table 4-3. Summary of Tukey pairwise comparison results of specific gravity and absorption of ACBFS and dolomite coarse aggregates. ......................... 45 Table 4-4. L.A. abrasion test results. ................................................................................ 45 Table 4-5. Summary of Tukey pair wise comparison results of percent mass loss of ACBFS and dolomite coarse aggregate from L.A abrasion test. ....... 46 Table 4-6. Slumps, w/cm and the dosage of water reducer data....................................... 51 Table 4-7. Air content, unit weight, w/cm and the dosage of air entraining agent in concrete mixtures. ............................................................................ 53 Table 4-8. Tukey pair wise comparison test results of 28-day compressive strength. ..... 57 Table 4-9. Tukey pair wise comparison test results of the compressive strength of control 2 (C2) specimens. .......................................................................... 58
xi Table
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Table 4-10. Compressive strength of concrete specimens after the completion of exposure regime. ....................................................................................... 65 Table 4-11. Factors (parameters) and their levels studied in factorial design. ................. 66 Table 4-12. The least square (LS) means values for percent difference in the compressive of FT and WD specimens exposed to deicers when compared to the compressive strength of control set 1 (C1) specimens........ 66 Table 4-13. The results of the analysis of variance (ANOVA) for the differences in compressive strength of FT and WD specimens exposed to deicers when compared to the compressive strength of control set 1 (C1) specimens.......................................................................... 67 Table 4-14. The results of Tukey’s multiple comparison analysis on the effects of the type of binder system on the change in compressive strength of FT and WD concretes exposed to deicers when compared to the compressive strength of control set 1 (C1) specimens. ....................... 68 Table 4-15. The results of Tukey’s multiple comparison analysis on the effects of the type of deicer on the change in compressive strength of FT and WD concretes exposed to deicers when compared to the compressive strength of control set 1 (C1) specimens. ................................. 68 Table 4-16. The least square (LS) means values for percent difference in the compressive strength of FT and WD specimens exposed to deicers when compared to the compressive strength of control set 2 (C2) specimens. ...................................................................................................... 70 Table 4-17. The results of the analysis of variance (ANOVA) for the differences in compressive strength of FT and WD specimens exposed to deicers after exposure and control set 2 specimens (C2). ........... 71 Table 4-18. The results of Tukey’s multiple comparison analysis on the effects of the type of binder system on the change in compressive strength of concrete after exposure period when compared to control set 2 (C2) specimens.......................................................................... 72
xii Table
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Table 4-19. The results of Tukey’s multiple comparison analysis on the effects of the type of deicers on the change in compressive strength of FT and WD concretes exposed to deicers when compared to control set 2 specimens (C2). ..................................................................................... 72 Table 4-20. Changes in the final RDME values with respect to the initial values. .......... 76 Table 4-21. The least square (LS) means values for the differences (before and after exposure) in RDME values of FT and WD specimens exposed to deicers. ......................................................................................... 77 Table 4-22. The results of the analysis of variance (ANOVA) for the differences (before and after exposure) in RDME values of FT and WD specimens exposed to deicers. ....................................................................... 78 Table 4-23. The results of Tukey’s multiple comparison analysis on the effects of the type of binder system on the change in RDME values of concrete after exposure period when compared the initial RDME values. ... 79 Table 4-24. The results of Tukey’s multiple comparison analysis on the effects of the type of deicers on the change in RDME values of concrete after exposure period when compared the initial RDME values. ... 79 Table 4-25. The changes in the final mass values with respect to the initial values. ....... 81 Table 4-26. The least square (LS) means values for the mass changes of FT and WD specimens exposed to deicers after exposure with respect to the initial mass values. ............................................................................... 82 Table 4-27. The results of the analysis of variance (ANOVA) for the mass changes of FT and WD specimens exposed to deicers after exposure with respect to the initial value. ..................................................... 83 Table 4-28. The results of Tukey’s multiple comparison analysis on the effects of the type of binder system on the change in mass values of concrete after exposure period when compared the initial value. ............. 84
xiii Table
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Table 4-29. The results of Tukey’s multiple comparison analysis on the effects of the type of deicers on the change in mass values of concrete after exposure period when compared the initial value. ................. 84 Table 4-30. The changes in the final length values with respect to the initial length values. ................................................................................................. 86 Table 4-31. The least square (LS) means values for the length changes of FT and WD specimens exposed to deicers after exposure with respect to the initial length values. ................................................................ 87 Table 4-32. The results of the analysis of variance (ANOVA) for the length changes of FT and WD specimens exposed to deicers after exposure with respect to the initial length values. ......................................... 88 Table 4-33. The results of Tukey’s multiple comparison analysis on the effects of the type of binder system on the change in length values of concrete specimen after exposure period when compared the initial length values. ................................................................................. 89 Table 4-34. The results of Tukey’s multiple comparison analysis on the effects of the type of deicers on the change in length values of concrete specimen after exposure period when compared the initial length values. ....................................................................................... 89 Table 4-35. The average chloride penetration depth for all concrete mixtures used in this study and exposed to different deicers under FT and WD conditions. ..................................................................................... 103 Table 4-36. The results of the analysis of variance (ANOVA) for the chloride ions penetration depth of FT and WD specimens exposed to deicers. ..................................................................................................... 104 Table 4-37. The least squares (LS) mean values for the chloride ions penetration depth of FT and WD specimens exposed to deicers. ................................... 105
xiv Table
Page
Table 4-38. The results (p-values) of Tukey’s multiple comparison analysis of the effects of the type of binder system on the chloride ions penetration depth values of concrete specimens. ......................................... 106 Table 4-39. The results (p-values) of Tukey’s multiple comparison analysis of the effects of the type of deicer on the chloride ions penetration depth values of concrete specimen. ............................................................. 106 Table 4-40. Concentration of elements and ions in the pore solution extracted from paste specimens with different binders. .............................................. 118
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LIST OF FIGURES
Figure
Page
Figure 2-1. Relationship between absorption, bulk specific gravity, and ACBFS particle size (Edw. C. Levy Company 2010) [14]. .......................................... 9 Figure 3-1. An example of mixture’s labeling scheme. .................................................... 30 Figure 4-1. Aggregate gradation curves............................................................................ 43 Figure 4-2. (A) Desorption curves of 24-hour saturated ACBFS and dolomite coarse aggregates and (B) the normalized desorption curves by the 24-hour water absorption. .............................................................................. 47 Figure 4-3. Ionic species content and the pH values of the leachates of ACBFS and dolomite: (A) Cl- and SO42- and (B) Na+, K+ and the total of Na+ + K+. ........................................................................................... 48 Figure 4-4. The amount of ions leached from ACBFS coarse aggregate to the synthesized pore solution: (A) Sulfate, (B) Sodium and (C) Potassium. ...... 50 Figure 4-5. Slump variations for mixtures with ACBFS and dolomite aggregates. ......... 52 Figure 4-6. Air content and unit weight of fresh concrete mixtures. ................................ 54 Figure 4-7. The average compressive strengths of control set 1 (C1) and control set 2 (C2) concretes. .......................................................................... 56 Figure 4-8. Compressive strengths of specimens from different concrete mixtures after the completion of exposure to deicers while undergoing: (A) freezing-thawing (FT) testing, and (B) wetting -drying (WD) testing...................................................................................... 59 Figure 4-9. Percent change in compressive strength of test specimens after: (A) exposure to freezing-thawing (FT) cycles, and (B) exposure to wetting-drying (WD) cycles with respect to 28-day compressive strength of control mixture (C1). ................................................................... 61
xvi Figure
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Figure 4-10. Percent change in compressive strength of test specimens after: (A) exposure to freezing-thawing (FT) cycles, and (B) exposure to wetting-drying (WD) cycles with respect to control C2. ............................... 63 Figure 4-11. Flexural strength of concrete after 7 and 56 days of moist curing. .............. 73 Figure 4-12. Physical changes in the appearance of the representative sample of M1-1PC-ACBFS (Plain – ACBFS) concrete specimens exposed to CaCl2 after (from left to right) 35, 59 and 102 FT cycles. This specimen failed after 111 FT cycles. ..................................................... 90 Figure 4-13. Physical changes in the appearance of the representative sample of M5-1PC-NA (Plain – Dolomite) concrete specimens exposed to CaCl2 after (from left to right) 42, 65, 118 and 139 FT cycles. This specimen failed after 151 FT cycles. ..................................................... 91 Figure 4-14. Physical changes in the appearance of the representative sample of M1-1PC-ACBFS (Plain – ACBFS) concrete specimens exposed to CaCl2 after (from left to right) 176, 205 and 281 WD cycles. .................. 92 Figure 4-15. Physical changes in the appearance of the representative sample of M5-1PC-NA (Plain – Dolomite) concrete specimens exposed to CaCl2 after (from left to right) 176, 205 and 281 WD cycles........................ 93 Figure 4-16. Physical changes in the appearance of the representative sample of M5-1PC-NA (Plain-Dolomite) concrete specimens exposed to MgCl2 after (from left to right) 42, 65, 139 and 350 FT cycles. ................... 94 Figure 4-17. Physical changes in the appearance of the representative sample of M5-1PC-NA (Plain-Dolomite) concrete specimens exposed to NaCl after (from left to right) 42, 65, 139 and 350 FT cycles. ...................... 94 Figure 4-18. Physical changes in the appearance of the representative sample of M5-1PC-NA (Plain - Dolomite) concrete specimens exposed to distilled water (DST) after (from left to right) 42, 65, 139 and 350 FT cycles. ....................................................................................................... 95
xvii Figure
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Figure 4-19. Physical changes in the appearance of the representative sample of M6-.2FA.8PC-NA (Fly ash - Dolomite) concrete specimens exposed to CaCl2 after (from left to right) 42, 65, 139 and 350 FT cycles. ................................................................................................ 96 Figure 4-20. Physical changes in the appearance of the representative sample of M6-.2FA.8PC-NA (Fly ash - Dolomite) concrete specimens exposed to MgCl2 after (from left to right) 42, 65, 139 and 350 FT cycles. ................................................................................................ 96 Figure 4-21. Physical changes in the appearance of the representative sample of M6-.2FA.8PC-NA (Fly ash - Dolomite) concrete specimens exposed to NaCl after (from left to right) 42, 65, 139 and 350 FT cycles. ................................................................................................ 97 Figure 4-22. Physical changes in the appearance of the representative sample of M6-.2FA.8PC-NA (Fly ash - Dolomite) concrete specimens exposed to distilled water (DST) after (from left to right) 42, 65, 139 and 350 FT cycles. .................................................................................. 97 Figure 4-23. Physical changes in the appearance of the representative sample of M7-.25SC.75PC-NA (Slag cement - Dolomite) concrete specimens exposed to CaCl2 after (from left to right) 3, 87 and 172 FT cycles. ................................................................................................ 98 Figure 4-24. Physical changes in the appearance of the representative sample of M7-.25SC.75PC-NA (Slag cement - Dolomite) concrete specimens exposed to MgCl2 after (from left to right) 3, 87 and 172 FT cycles. ................................................................................................ 98 Figure 4-25. Physical changes in the appearance of the representative sample of M7-.25SC.75PC-NA (Slag cement - Dolomite) concrete specimens exposed to NaCl after (from left to right) 3, 87 and 172 FT cycles. ................................................................................................ 99
xviii Figure
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Figure 4-26. Physical changes in the appearance of the representative sample of M7-.25SC.75PC-NA (Slag cement - Dolomite) concrete specimens exposed to distilled water (DST) after (from left to right) 3 and 172 FT cycles. ............................................................................ 99 Figure 4-27. Physical changes in the appearance of the representative sample of M8-.17FA.23SC.6PC-NA (Ternary - Dolomite) concrete specimens exposed to CaCl2 after (from left to right) 3, 87 and 172 FT cycles. .............................................................................................. 100 Figure 4-28. Physical changes in the appearance of the representative sample of M8-.17FA.23SC.6PC-NA (Ternary - Dolomite) concrete specimens exposed to MgCl2 after (from left to right) 3, 87 and 172 FT cycles. .............................................................................................. 100 Figure 4-29. Physical changes in the appearance of the representative sample of M8-.17FA.23SC.6PC-NA (Ternary - Dolomite) concrete specimens exposed to NaCl after (from left to right) 3, 87 and 172 FT cycles. .............................................................................................. 101 Figure 4-30. Physical changes in the appearance of the representative sample of M8-.17FA.23SC.6PC-NA (Ternary - Dolomite) concrete specimens exposed to distilled water (DST) after (from left to right) 3, 87and 172 FT cycles. ..................................................................... 101 Figure 4-31. An example of cross section of specimen with its location within the original beam. ........................................................................................ 102 Figure 4-32. An example of SEM sample and the location from which it was obtained. ............................................................................................... 107 Figure 4-33. Deposits of Friedel’s salt and remnants of unreacted binders (fly ash and slag cement) found in SEM sample extracted from M4 (Ternary-ACBFS) specimen exposed to CaCl2 after 310 FT cycles. .......... 108
xix Figure
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Figure 4-34. Deposits of Friedel’s salt and remnants of unreacted binders (fly ash and slag cement) found in SEM sample extracted from M8 (Ternary-Dolomite) specimen exposed to MgCl2 after 310 FT cycles........ 108 Figure 4-35. SEM - EDX micrographs for specimen from M1 (Plain-ACBFS) mixture – exposed to CaCl2 after 111 FT cycles; (A) & (B) Friedel’s salt, (C) & (D) chloride deposits within the paste. ....................... 109 Figure 4-36. SEM - EDX micrographs of microstructure of specimen removed from the corner of a beam from M5 (Plain – Dolomite) mixture exposed to CaCl2 after 151 FT cycles; (A) & (B) chloride deposits within C-S-H, (C) Friedel’s salt, (D) deposit of CaCl2 within C-S-H. ........ 110 Figure 4-37. SEM-EDX micrographs of brucite, M-S-H, calcium hydroxide and remnants of un-hydrated cement (C3A) found in M7 (Slag cement-Dolomite) specimen exposed to MgCl2 after 310 FT cycles. .............................................................................................. 111 Figure 4-38. SEM-EDX micrographs of M-S-H, CaCl2, CH, calcium carbonate, MgCl2 and remnant of un-hydrated slag cement found in M3 (Slag cement-ACBFS) specimen exposed to MgCl2 after 226 WD cycles. ............................................................................................ 111 Figure 4-39. Void filled with (A) calcium oxychloride-like phase in sample exposed to CaCl2 solution and (B) 1000X magnification image of Mg-O-Cl phase surrounded by calcium hydroxide (CH) in M1 (Plain-ACBFS) specimen exposed to MgCl2 after 347 FT cycles. ............. 112 Figure 4-40. SEM image showing deposits of calcium sulfide (CaS) inside ACBFS particle. ........................................................................................... 112 Figure 4-41. SEM images showing the presence of calcium sulfide in the particles of ACBFS aggregate and Friedel’s salt in the matrix of M3 (Slag cement-ACBFS) specimen exposed to NaCl after 310 FT cycles. .............................................................................................. 113
xx Figure
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Figure 4-42. CaS deposits and empty voids in ACBFS particle from M4 (Ternary-ACBFS) specimen exposed to distilled water (DST) after 310 FT cycles. ..................................................................................... 114 Figure 4-43. SEM-EDX (Energy Dispersive X-Ray) Micrographs of ettringite in (A) concrete containing ACBFS and slag cement (M3-DST-FT)) and (B) concrete containing natural dolomite as coarse aggregates. ........... 115 Figure 4-44. Concentration of ionic species and pH of different concrete leachates: (A) anions (chloride and sulfate), (B) cations (sodium, potassium and total of both ions). ................................................................ 116 Figure 4-45. Variation of the concentration of alkali ions in the pore solution with different age: (A) Sodium ions, (B) Potassium ions. ............. 119 Figure 4-46. Variation in total alkalis concentration with age in different paste mixtures. ............................................................................................. 120 Figure 4-47. Variation in sulfate ion concentration with age for different paste mixtures. ............................................................................................. 121 Appendix Figure
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Figure A-1. Mill certificate for cement used in this study .............................................. 139 Figure A-2. Class C fly ash certificate from the producer .............................................. 140 Figure A-3. Air-cooled blast furnace slag (ACBFS) aggregate certificate from the producer. ....................................................................................... 141 Figure B-1. Relative dynamic modulus of elasticity (RDME) of control specimens (C2) and specimens exposed to different deicers under freezing-thawing (FT) cycles; (A) M1, (B) M2, (C) M3 and (D) M4. ........ 142 Figure B-2. Relative dynamic modulus of elasticity (RDME) of control specimens (C2) and specimens exposed to different deicers under freezing-thawing (FT) cycles; (A) M5, (B) M6, (C) M7 and (D) M8. ........ 143 Figure B-3. Relative dynamic modulus of elasticity (RDME) of control specimens (C2) and specimens exposed to different deicers under wetting-drying (WD) cycles; (A) M1, (B) M2, (C) M3 and (D) M4. ......... 144
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Figure B-4. Relative dynamic modulus of elasticity (RDME) of control specimens (C2) and specimens exposed to different deicers under wetting-drying (WD) cycles; (A) M5, (B) M6, (C) M7 and (D) M8. ......... 145 Figure B-5. Relative mass change of control specimens (C2) and specimens exposed to different deicers under freezing-thawing (FT) cycles; (A) M1, (B) M2, (C) M3 and (D) M4.......................................................... 146 Figure B-6. Relative mass change of control specimens (C2) and specimens exposed to different deicers under freezing-thawing (FT) cycles; (A) M5, (B) M6, (C) M7 and (D) M8.......................................................... 147 Figure B-7. Relative mass change of control specimens (C2) and specimens exposed to different deicers under wetting-drying (WD) cycles; (A) M1, (B) M2, (C) M3 and (D) M4.......................................................... 148 Figure B-8. Relative mass change of control specimens (C2) and specimens exposed to different deicers under wetting-drying (WD) cycles; A) M5, (B) M6, (C) M7 and (D) M8. .......................................................... 149 Figure B-9. The average length changes of specimens subjected different deicers and FT cycles: (A) M1, (B) M2, (C) M3 and (D) M4. .................... 150 Figure B-10. The average length changes of specimens subjected different deicers and FT cycles: (A) M5, (B) M6, (C) M7 and (D) M8. .................... 151 Figure B-11. The average length changes of specimens subjected different deicers and WD cycles: (A) M1, (B) M2, (C) M3 and (D) M4. .................. 152 Figure B-12. The average length changes of specimens subjected different deicers and WD cycles: (A) M5, (B) M6, (C) M7 and (D) M8. .................. 153 Figure B-13. Physical changes in the appearance of M1-1PC-ACBFS (Plain-ACBFS) concrete specimen exposed to CaCl2 after (from left to right) 35, 59 and 102 FT cycles. ............................................. 154 Figure B-14. Physical changes in the appearance of M1-1PC-ACBFS (Plain-ACBFS) concrete specimen exposed to MgCl2 after (from left to right) 35, 59, 102 and 347 FT cycles. ..................................... 154
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Figure B-15. Physical changes in the appearance of M1-1PC-ACBFS (Plain-ACBFS) concrete specimen exposed to NaCl after (from left to right) 35, 59, 102 and 347 FT cycles. ..................................... 154 Figure B-16. Physical changes in the appearance of M1-1PC-ACBFS (Plain-ACBFS) concrete specimen exposed to distilled water (DST) after (from left to right) 35, 59, 102 and 347 FT cycles. .................. 155 Figure B-17. Physical changes in the appearance of M2-.2FA.8PC-ACBFS (Fly ash-ACBFS) concrete specimen exposed to CaCl2 after (from left to right) 35, 59, 102 and 347 FT cycles. ..................................... 155 Figure B-18. Physical changes in the appearance of M2-.2FA.8PC-ACBFS (Fly ash-ACBFS) concrete specimen exposed to MgCl2 after (from left to right) 35, 59, 102 and 347 FT cycles. ..................................... 155 Figure B-19. Physical changes in the appearance of M2-.2FA.8PC-ACBFS (Fly ash-ACBFS) concrete specimen exposed to NaCl after (from left to right) 35, 59, 102 and 347 FT cycles. ..................................... 156 Figure B-20. Physical changes in the appearance of M2-.2FA.8PC-ACBFS (Fly ash-ACBFS) concrete specimen exposed to distilled water (DST) after (from left to right) 35, 59, 102 and 347 FT cycles. .................. 156 Figure B-21. Physical changes in the appearance of M3-.25SC.75PCACBFS (Slag cement-ACBFS) concrete specimen exposed to CaCl2 after (from left to right) 18, 191 and 310 FT cycles.......................... 156 Figure B-22. Physical changes in the appearance of M3-.25SC.75PCACBFS (Slag cement-ACBFS) concrete specimen exposed to MgCl2 after (from left to right) 18, 191 and 310 FT cycles. ....................... 157 Figure B-23. Physical changes in the appearance of M3-.25SC.75PCACBFS (Slag cement-ACBFS) concrete specimen exposed to NaCl after (from left to right) 18, 191 and 310 FT cycles. .......................... 157
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Figure B-24. Physical changes in the appearance of M3-.25SC.75PCACBFS (Slag cement-ACBFS) concrete specimen exposed to distilled water (DST) after (from left to right) 18, 191 and 310 FT cycles. .............................................................................................. 157 Figure B-25. Physical changes in the appearance of M4-.17FA.23SC.6PCACBFS (Ternary-ACBFS) concrete specimen exposed to CaCl2 after (from left to right) 18, 191 and 310 FT cycles. ................................... 158 Figure B-26. Physical changes in the appearance of M4-.17FA.23SC.6PCACBFS (Ternary-ACBFS) concrete specimen exposed to MgCl2 after (from left to right) 18, 191 and 310 FT cycles. ................................... 158 Figure B-27. Physical changes in the appearance of M4-.17FA.23SC.6PCACBFS (Ternary-ACBFS) concrete specimen exposed to NaCl after (from left to right) 18, 191 and 310 FT cycles. ................................... 158 Figure B-28. Physical changes in the appearance of M4-.17FA.23SC.6PCACBFS (Ternary-ACBFS) concrete specimen exposed to distilled water (DST) after (from left to right) 18, 191 and 310 FT cycles. .............. 159 Figure B-29. Physical changes in the appearance of M5-.1PC-NA (PlainDolomite) concrete specimen exposed to CaCl2 after (from left to right) 42, 65, 118 and 139 FT cycles. ...................................................... 159 Figure B-30. Physical changes in the appearance of M5-.1PC-NA (PlainDolomite) concrete specimen exposed to MgCl2 after (from left to right) 42, 65, 139 and 350 FT cycles. ...................................................... 159 Figure B-31. Physical changes in the appearance of M5-.1PC-NA (PlainDolomite) concrete specimen exposed to NaCl after (from left to right) 42, 65, 139 and 350 FT cycles. ...................................................... 160 Figure B-32. Physical changes in the appearance of M5-.1PC-NA (PlainDolomite) concrete specimen exposed to distilled water (DST) after (from left to right) 42, 65, 139 and 350 FT cycles. ............................. 160
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Figure B-33. Physical changes in the appearance of M6-.2FA.8PC-NA (Fly ash-Dolomite) concrete specimen exposed to CaCl2 after (from left to right) 42, 65, 139 and 350 FT cycles. ..................................... 160 Figure B-34. Physical changes in the appearance of M6-.2FA.8PC-NA (Fly ash-Dolomite) concrete specimen exposed to MgCl2 after (from left to right) 42, 65, 139 and 350 FT cycles. ..................................... 161 Figure B-35. Physical changes in the appearance of M6-.2FA.8PC-NA (Fly ash-Dolomite) concrete specimen exposed to NaCl after (from left to right) 42, 65, 139 and 350 FT cycles. ..................................... 161 Figure B-36. Physical changes in the appearance of M6-.2FA.8PC-NA (Fly ash-Dolomite) concrete specimen exposed to distilled water (WD) after (from left to right) 42, 65, 139 and 350 FT cycles. ................... 161 Figure B-37. Physical changes in the appearance of M7-.25SC.75PC-NA (Slag cement - Dolomite) concrete specimen exposed to CaCl2 after (from left to right) 3, 87 and 172 FT cycles. ....................................... 162 Figure B-38. Physical changes in the appearance of M7-.25SC.75PC-NA (Slag cement - Dolomite) concrete specimen exposed to MgCl2 after (from left to right) 3, 87 and 172 FT cycles. ....................................... 162 Figure B-39. Physical changes in the appearance of M7-.25SC.75PC-NA (Slag cement - Dolomite) concrete specimen exposed to NaCl after (from left to right) 3, 87 and 172 FT cycles. ............................................... 162 Figure B-40. Physical changes in the appearance of M7-.25SC.75PC-NA (Slag cement - Dolomite) concrete specimen exposed to distilled water (DST) after (from left to right) 3 and 172 FT cycles. ........................ 163 Figure B-41. Physical changes in the appearance of M8-.17FA.23SC.6PC-NA (Ternary - Dolomite) concrete specimen exposed to CaCl2 after (from left to right) 3, 87 and 172 FT cycles. ............................................... 163
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Figure B-42. Physical changes in the appearance of M8-.17FA.23SC.6PC-NA (Ternary - Dolomite) concrete specimen exposed to MgCl2 after (from left to right) 3, 87 and 172 FT cycles. ............................................... 163 Figure B-43. Physical changes in the appearance of M8-.17FA.23SC.6PC-NA (Ternary - Dolomite) concrete specimen exposed to NaCl after (from left to right) 3, 87 and 172 FT cycles. ............................................... 164 Figure B-44. Physical changes in the appearance of M8-.17FA.23SC.6PC-NA (Ternary - Dolomite) concrete specimen exposed to distilled water (DST) after (from left to right) 3, 87and 172 FT cycles. ................... 164 Figure B-45. Physical changes in the appearance of M1-1PC-ACBFS (Plain-ACBFS) concrete specimen exposed to CaCl2 after (from left to right) 176, 205 and 281 WD cycles. ....................................... 164 Figure B-46. Physical changes in the appearance of M1-1PC-ACBFS (Plain-ACBFS) concrete specimen exposed to MgCl2 after (from left to right) 176, 205 and 281 WD cycles. ....................................... 165 Figure B-47. Physical changes in the appearance of M1-1PC-ACBFS (Plain-ACBFS) concrete specimen exposed to NaCl after (from left to right) 176, 205 and 281 WD cycles. ....................................... 165 Figure B-48. Physical changes in the appearance of M1-1PC-ACBFS (Plain-ACBFS) concrete specimen exposed to distilled water (DST) after (from left to right) 176, 205 and 281 WD cycles. .................... 165 Figure B-49. Physical changes in the appearance of M2-.2FA.8PC-ACBFS (Fly ash-ACBFS) concrete specimen exposed to CaCl2 after (from left to right) 176, 205 and 281 WD cycles. ....................................... 166 Figure B-50. Physical changes in the appearance of M2-.2FA.8PC-ACBFS (Fly ash-ACBFS) concrete specimen exposed to MgCl2 after (from left to right) 176, 205 and 281 WD cycles. ....................................... 166
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Figure B-51. Physical changes in the appearance of M2-.2FA.8PC-ACBFS (Fly ash-ACBFS) concrete specimen exposed to NaCl after (from left to right) 176, 205 and 281 WD cycles. ....................................... 166 Figure B-52. Physical changes in the appearance of M2-.2FA.8PC-ACBFS (Fly ash-ACBFS) concrete specimen exposed to distilled water (DST) after (from left to right) 176, 205 and 281 WD cycles. .................... 167 Figure B-53. Physical changes in the appearance of M3-.25SC.75PC-ACBFS (Slag cement-ACBFS) concrete specimen exposed to CaCl2 after (from left to right) 0, 90 and 226 WD cycles. ............................................. 167 Figure B-54. Physical changes in the appearance of M3-.25SC.75PC-ACBFS (Slag cement-ACBFS) concrete specimen exposed to MgCl2 after (from left to right) 0, 90 and 226 WD cycles. ............................................. 167 Figure B-55. Physical changes in the appearance of M3-.25SC.75PC-ACBFS (Slag cement-ACBFS) concrete specimen exposed to NaCl after (from left to right) 0, 90 and 226 WD cycles. ............................................. 168 Figure B-56. Physical changes in the appearance of M3-.25SC.75PC-ACBFS (Slag cement-ACBFS) concrete specimen exposed to distilled water (DST) after (from left to right) 0, 90 and 226 WD cycles. ................ 168 Figure B-57. Physical changes in the appearance of M4-.17FA.23SC.6PCACBFS (Ternary-ACBFS) concrete specimen exposed to CaCl2 after (from left to right) 0, 90 and 226 WD cycles. ..................................... 168 Figure B-58. Physical changes in the appearance of M4-.17FA.23SC.6PCACBFS (Ternary-ACBFS) concrete specimen exposed to MgCl2 after (from left to right) 0, 90 and 226 WD cycles. ..................................... 169 Figure B-59. Physical changes in the appearance of M4-.17FA.23SC.6PCACBFS (Ternary-ACBFS) concrete specimen exposed to NaCl after (from left to right) 0, 90 and 226 WD cycles. ..................................... 169
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Figure B-60. Physical changes in the appearance of M4-.17FA.23SC.6PCACBFS (Ternary-ACBFS) concrete specimen exposed to distilled water (DST) after (from left to right) 0, 90 and 226 WD cycles. ................ 169 Figure B-61. Physical changes in the appearance of M5-1PC-NA (Plain-Dolomite) concrete specimen exposed to CaCl2 after (from left to right) 176, 205 and 281 WD cycles. ....................................... 170 Figure B-62. Physical changes in the appearance of M5-1PC-NA (Plain-Dolomite) concrete specimen exposed to MgCl2 after (from left to right) 176, 205 and 281 WD cycles. ....................................... 170 Figure B-63. Physical changes in the appearance of M5-1PC-NA (Plain-Dolomite) concrete specimen exposed to NaCl after (from left to right) 176, 205 and 281 WD cycles. ....................................... 170 Figure B-64. Physical changes in the appearance of M5-1PC-NA (Plain-Dolomite) concrete specimen exposed to distilled water (DST) after (from left to right) 176, 205 and 281 WD cycles. .................... 171 Figure B-65. Physical changes in the appearance of M6-.2FA.8PC-NA (Fly ash-Dolomite) concrete specimen exposed to CaCl2 after (from left to right) 176, 205 and 281 WD cycles. ....................................... 171 Figure B-66. Physical changes in the appearance of M6-.2FA.8PC-NA (Fly ash-Dolomite) concrete specimen exposed to MgCl2 after (from left to right) 176, 205 and 281 WD cycles. ....................................... 171 Figure B-67. Physical changes in the appearance of M6-.2FA.8PC-NA (Fly ash-Dolomite) concrete specimen exposed to NaCl after (from left to right) 176, 205 and 281 WD cycles. ....................................... 172 Figure B-68. Physical changes in the appearance of M6-.2FA.8PC-NA (Fly ash-Dolomite) concrete specimen exposed to distilled water (DST) after (from left to right) 176, 205 and 281 WD cycles. .................... 172
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Figure B-69. Physical changes in the appearance of M7-.25SC.75PC-NA (Slag cement-Dolomite) concrete specimen exposed to CaCl2 after (from left to right) 0, 90 and 226 WD cycles. ..................................... 172 Figure B-70. Physical changes in the appearance of M7-.25SC.75PC-NA (Slag cement-Dolomite) concrete specimen exposed to MgCl2 after (from left to right) 0, 90 and 226 WD cycles. ..................................... 173 Figure B-71. Physical changes in the appearance of M7-.25SC.75PC-NA (Slag cement-Dolomite) concrete specimen exposed to NaCl after (from left to right) 0, 90 and 226 WD cycles. ..................................... 173 Figure B-72. Physical changes in the appearance of M7-.25SC.75PC-NA (Slag cement-Dolomite) concrete specimen exposed to distilled water (DST) after (from left to right) 0, 90 and 226 WD cycles. ................ 173 Figure B-73. Physical changes in the appearance of M8-.17FA.23SC.6PCNA (Ternary-Dolomite) concrete specimen exposed to CaCl2 after (from left to right) 0, 90 and 226 WD cycles. ..................................... 174 Figure B-74. Physical changes in the appearance of M8-.17FA.23SC.6PCNA (Ternary-Dolomite) concrete specimen exposed to MgCl2 after (from left to right) 0, 90 and 226 WD cycles. ..................................... 174 Figure B-75. Physical changes in the appearance of M8-.17FA.23SC.6PCNA (Ternary-Dolomite) concrete specimen exposed to NaCl after (from left to right) 0, 90 and 226 WD cycles. ..................................... 174 Figure B-76. Physical changes in the appearance of M8-.17FA.23SC.6PCNA (Ternary-Dolomite) concrete specimen exposed to distilled water (DST) after (from left to right) 0, 90 and 226 WD cycles. ................ 175 Figure B-77. Chloride penetration depths associated with different deicers in M1-1PC-ACBFS (Plain-ACBFS) specimens after: (A) 347 FT cycles and (B) 286 WD cycles. .............................................................. 176
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Figure B-78. Chloride penetration depths associated with different deicers in M2-.2FA.8PC-ACBFS (Fly ash-ACBFS) specimens after: (A) 347 FT cycles and (B) 286 WD cycles. ................................................ 177 Figure B-79. Chloride penetration depths associated with different deicers in M3-.25SC.75PC-ACBFS (Slag cement-ACBFS) specimens after: (A) 310 FT cycles and (B) 226 WD cycles. ....................................... 178 Figure B-80. Chloride penetration depths associated with different deicers in M4-.17FA.23SC.6PC-ACBFS (Ternary-ACBFS) specimens after: (A) 310 FT cycles and (B) 226 WD cycles. ....................................... 179 Figure B-81. Chloride penetration depths associated with different deicers in M1-1PC-NA (Plain-Dolomite) specimens after: (A) 350 FT cycles and (B) 286 WD cycles..................................................................... 180 Figure B-82. Chloride penetration depths associated with different deicers in M6-.2FA.8PC-NA (Fly ash-Dolomite) specimens after: (A) 350 FT cycles and (B) 286 WD cycles. ................................................ 181 Figure B-83. Chloride penetration depths associated with different deicers in M7-.25SC.75PC-NA (Slag cement-Dolomite) specimens after: (A) 310 FT cycles and (B) 226 WD cycles. ................................................ 182 Figure B-84. Chloride penetration depths associated with different deicers in M8-.17FA.23SC.6PC-NA (Ternary-Dolomite) specimens after: (A) 310 FT cycles and (B) 226 WD cycles. ................................................ 183 Figure C-1. SEM - EDX micrographs for M1 (Plain-ACBFS) beam exposed to MgCl2 after 347 FT cycles; (A) Mg-O-Cl, (B) M-S-H, (C) and (D) ettringite. ............................................................................................... 184 Figure C-2. SEM - EDX micrographs for M1 (Plain – Dolomite) beam exposed to MgCl2 after 347 FT cycles; (A) NaCl deposit, (B) Ettingite, (C) Ettringite and Friedel’s salt (D) Chloride in paste. ............................... 185
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Figure C-3. SEM - EDX micrographs for M1 (Plain-NaCl) specimen exposed to distilled water (DST) after 347 FT cycles; (A)&(B) ettringite, (C) Portlandite/Ca(OH)2, (D) C-S-H ........................................................... 186 Figure C-4. SEM - EDX micrographs for M2 (Fly ash-ACBFS) specimen exposed to CaCl2 after 347 FT cycles; (A) CaCl2, (B) Friedel’s salt and ettringite, (C) Ettringite (D) Cl- deposits within the paste. ............ 187 Figure C-5. SEM - EDX micrographs for M2 (Fly ash-ACBFS) specimen exposed to MgCl2 after 347 FT cycles; (A) Cl- and sulfate deposits in the matrix, (B) Brucite layer, (C) Ettringite and Friedel’s salt in void, (D) Mg-O-Cl. ............................................................ 188 Figure C-6. SEM - EDX micrographs for M2 (Fly ash-ACBFS) specimen exposed to NaCl after 347 FT cycles; (A) Cl- deposits in the matrix, (B) Friedel’s salt, (C) Ettringite and (D) NaCl deposit. .............................. 189 Figure C-7. SEM - EDX micrographs for M3 (Slag cement-ACBFS) specimen exposed to CaCl2 after 310 FT cycles.......................................................... 190 Figure C-8. SEM - EDX micrographs for M4 (Ternary-ACBFS) specimen exposed to MgCl2 after 310 FT cycles. ....................................................... 191 Figure C-9. SEM - EDX micrographs for M4 (Ternary-ACBFS) specimen exposed to NaCl after 310 FT cycles; (A) & (B) Friedel’s salt, (C) Sulfate deposit in pore (D) Cl- deposits in the matrix. .......................... 192 Figure C-10. SEM - EDX micrographs for M4 (Ternary-ACBFS) specimen exposed to distilled water (DST) after 310 FT cycles. ................................ 193 Figure C-11. SEM - EDX micrographs for M5 (Plain-Dolomite) specimen exposed to CaCl2 after 151 FT cycles; (A) & (B) Cl- deposits in the matrix, (C) & (D) Friedel’s salt. ............................................................ 194 Figure C-12. SEM - EDX micrographs for M5 (Plain-Dolomite) specimen exposed to MgCl2 after 350 FT cycles; (A) & (B) Chloride enriched M-S-H, (C) & (D) Friedel’s salt. ................................................................. 195
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Figure C-13. SEM - EDX micrographs for M5 (Plain-Dolomite) specimen exposed to NaCl after 350 FT cycles; (A) & (B) Chloride deposits in C-S-H, (C) & (D) Friedel’s salt. .............................................................. 196 Figure C-14. SEM - EDX micrographs for M6 (Fly ash-Dolomite) specimen exposed to MgCl2 after 350 FT cycles; (A) & (B) Chloride enriched M-S-H, (C) Cl- deposits in C-S-H and (D) Friedel’s salt deposit. ............... 197 Figure C-15. SEM - EDX micrographs for M7 (Slag cement-Dolomite) specimen exposed to CaCl2 after 310 FT cycles. ........................................ 198 Figure C-16. SEM - EDX micrographs for M7 (Slag cement-Dolomite) specimen exposed to MgCl2 after 350 FT cycles; (A) & (B) M-S-H, (C) Friedel’s salt and (D) Cl- deposits in C-S-H. ........................... 199 Figure C-17. SEM - EDX micrographs for M8 (Ternary-Dolomite) specimen exposed to CaCl2 after 310 FT cycles.......................................................... 200 Figure C-18. SEM - EDX micrographs for M8 (Ternary-Dolomite) specimen exposed to MgCl2 after 310 FT cycles; (A) & (B) Brucite, (C) M-S-H and (D) Friedel’s salt................................................................. 201 Figure C-19. SEM - EDX micrographs for M8 (Ternary-Dolomite) specimen exposed to NaCl after 310 FT cycles; (A) & (B) Cl- deposits in C-S-H, (C) & (D) Friedel’s salt. .............................................................. 202 Figure C-20. SEM - EDX micrographs for M8 (Ternary-Dolomite) specimen exposed to distilled water (DST) after 310 FT cycles. ................................ 203
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LIST OF ABBREVIATIONS
AASHTO: American Association of State Highway and Transportation Officials ACBFS: Air-Cooled Blast Furnace Slag ANOVA: Analysis of Variance ASTM: American Society for Testing Material CA: Coarse Aggregate CH: Calcium Hydroxide CTE: Coefficient of Thermal Expansion DOT: Department of Transportation FA: Fly Ash FT: Freezing-Thawing IC: Ion Chromatography ICP: Inductively Coupled Plasma INDOT: Indiana Department of Transportation GGBFS: Ground Granulated Blast Furnace Slag NA: Natural Aggregate PC: Portland Cement, OPC: Ordinary Portland Cement QC/QA: Quality Control/Quality Assurance SC: Slag Cement SEM: Scanning Electron Microscopy WD: Wetting-Drying DST: Distilled Water SEM: Scanning Electron Microscopy C-S-H: Calcium Silicate Hydrate M-S-H: Magnesium Silicate Hydrate
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ABSTRACT
Verian, Kho Pin, Ph.D., Purdue University, December 2015. Influence of Air-cooled Blast Furnace Slag (ACBFS) Coarse Aggregate on Properties of Pavement Concrete Exposed to Freezing-Thawing and Wetting-Drying Conditions. Major Professor: Jan Olek. The main purpose of this research was to evaluate the influence of using aircooled blast furnace slag (ACBFS) coarse aggregate as a replacement for natural dolomite coarse aggregate in pavement concrete mixtures. All mixtures containing ACBFS were designed to meet the requirements of Indiana Department of Transportation (INDOT) specifications for pavement concrete. The scope of the study included evaluation and analysis of the effects of ACBFS on concrete properties in the presence of three different types of deicers (CaCl2, MgCl2 and NaCl).
These evaluations were
conducted under simulated temperature cycles that represented exposure to freezingthawing (FT) and wetting-drying (WD) conditions. A total of eight different concrete mixtures were produced in the course of this study. The mixtures were prepared using two types of coarse aggregates, ACBFS and (for comparison with the typical INDOT mixtures) dolomite. Four different binder systems were used, and included the following: (a) plain - 100% portland cement (PC), two types of binary binder systems (b) 20% fly ash (FA) + 80% PC and (c) 25% slag cement (SC) + 75% PC, and a single ternary system (d) 17% FA + 23% SC + 60% PC. Each of the mixture produced was used to prepare several types of specimens for laboratory testing. The test performed on fresh concrete included determination of slump, unit weigh and entrained air content. The mechanical properties of the hardened concrete were assessed by conducting compressive strength and flexural strength tests. The durability of concrete was assessed by periodical measurements of relative dynamic modulus of elasticity (RDME) and monitoring the length changes of the prismatic
xxxiv specimens. The changes in the physical appearance of specimens exposed to either FT or WD conditions were documented at different stages of the exposure cycles. The depth of chloride ion penetration was measured after the completion of exposure period. The combined effects of the deicer/exposure conditions on the microstructure of the concrete were evaluated using scanning electron microscopy (SEM) analysis on the specimens after the completion of the exposure test. The results from this study revealed that ACBFS is a viable option for coarse aggregate in pavement concrete. The usage of fly ash, slag cement and the combination of both as partial replacement of portland cement was found to not only improve concrete’s strength at later age but also to increase concrete durability in the presence of deicers and FT/WD exposure conditions. Among the three types of deicers studied, CaCl2 was found to be the most aggressive in terms of inducing damage to the concrete followed by MgCl2. Thus, it is advised that the use of these deicers on plain concrete pavements should be more strictly monitored and restricted to cases where other deicer cannot provide the required safety of the roadway.
Key words: air-cooled blast furnace slag (ACBFS), coarse aggregate, deicers, freezingthawing (FT), wetting-drying (WD), pavement concrete, durability properties, scanning electron microscopy (SEM), relative dynamic modulus of elasticity (RDME), plain concrete, binary mixtures, ternary mixtures.
1
CHAPTER 1. INTRODUCTION
Concrete, a composite material composed of aggregates, cement and water, is the most widely used man-made material in the world [1]. Concrete can be used in a wide range of application, such as buildings, bridges, dams and roads. Although many different types of concrete have been developed for different applications, they all share some common positive features which include: versatility, strength, durability, availability, fire resistance and comparatively low cost [2]. A report by Cement Sustainability Initiative (CSI), has estimated that roughly more than 25 billion tonnes of concrete were manufactured globally in 2009 and that amount keeps increasing each year [3]. As a result, the demand for concrete’s ingredients elevates proportionally to concrete production. Ordinary portland cement (OPC), is a dominant ingredient of concrete [2] serving as bonding agent once reacted with water through the hydration process. In typical concrete mixture, OPC occupies 10% to 15% of the total volume [4]. That requires manufacturing of high amount of cement in order to fulfill the needs in concrete construction. To meet that high demand, more than 4 billion tones of OPC were produced worldwide in 2013, and this number has increased in the following year [5]. Of concern to the cement industry is the fact that every tonne of OPC produced releases on average a similar amount of CO2 into the atmosphere [2], [6]. Another concern is related to the depletion of fossil fuels, which are used as the major energy source in cement production. Those challenges in cement industry have triggered a strong push toward the innovation in cement production, mainly with respect to reduction, or even elimination, the previously mentioned drawbacks cement production. In this regard, the use of other cementitious materials (i.e. fly ash and slag cement), which are by products of other
2 industry, have been proven to be a viable alternative. The development of other type of binders, as the type which result in lower CO2 emissions, is also being pursued [7]. The challenges related to concrete production are not only associated with the environmental impact of cement production itself, but also with the depletion of sources of natural aggregates. In general, natural aggregates used in concrete consist of crushed stone (or gravel) and sand. These ingredients occupy 70% to 80% of the volume of concrete mixture [4], [8], [9]. Although the natural aggregate sources are vast, they are, nevertheless, finite and facing depletion, especially in urban areas. The prospect of opening of a new aggregate source and the expansion of the existing aggregate quarries are often limited by the environmental regulations and land use policies [9]. Using other materials, such as air-cooled blast furnace slag (ACBFS) and recycled aggregate, as substitutes for natural aggregate, offers potential ways to address these concerns. In recent time, concrete production is also driven by efforts to improve its quality with strong focus on delivery of more durable, efficient and environmentally friendly concrete. In the United States, more than 83 million tonnes of concrete were produced in 2014, an increase from ~77 million tonnes produced during its previous year [5]. Part of this amount was used to construct new and to rehabilitate existing concrete pavements. More than 60% of nearly 45,000 miles of national highway system are constructed of concrete [10]. In addition, more than half of these concrete pavements are exposed to freezing temperatures during winter season [11]. The freeze-thaw and wet-dry cycles commonly occur during this season and they have been found to affect the performance and service life of the pavement [12], [13]. In addition to the weathering effects, the application of deicers to melt the snow and to prevent the formation of an icy layer on the surface of the pavement tends to cause concrete’s deterioration through chemical reaction mechanism [12], [13].
1.1
Background
As already mentioned, efforts to produce more sustainable concrete pavements have led to the use of alternative materials as a substitute for the generally used concrete
3 ingredients, i.e. cement and natural aggregates. It is estimated that the carbon dioxide (CO2) emitted from the cement production represents 5%-7% of the global CO2 emission [6]. Meanwhile, problems related to the availability of natural aggregates also emerge due to the depletion of existing sources, restrictions on developing new quarries and the increase in cost of mining and transportation [9]. In practice, fly ash and slag cement are commonly used as partial replacement of cement in concrete mixtures. In addition, the air-cooled blast furnace slag (ACBFS) has been used as source of coarse aggregate since at least the 1930s [14]. Recently however, some concerns arose regarding the use of ACBFS as coarse aggregate in concrete mixtures. These concerns appear to be related to the physical characteristic and the chemical composition of ACBFS [14]. Specific gravity (SG) and absorption are two aggregate properties which directly influence concrete mixture proportions. These two aggregate’s parameters have further affected the properties of concrete made with that aggregate [9]. The typical value of specific gravity of ACBFS ranges from 2.0 to 2.5. For comparison, the SG of natural coarse aggregate is typically in the range of 2.6 to 2.7 [9], [14]. The previous study by the current author also indicated that aggregate with a low value of specific gravity yields concrete with lower strength [9]. The absorption of ACBFS varies from 1% to 8%, depending on the particle size of the aggregate, and its relatively higher value compared to that of the most natural aggregate for which absorption is in the range of 0.5% to 3% [14]. In terms of chemical composition, the concern with respect to the use of ACBFS aggregates in concrete is related to their higher sulfate content. The sulfate found in the ACBFS aggregate is typically in the form of calcium sulfide (CaS) which forms in this aggregate as a result of the sulfur from the coke fuel reacting with calcium from the aggregate used as flux [14]. Both mechanical and chemical properties of ACBFS have influenced properties when it’s used as coarse aggregate in the concrete mixture. In terms of the application of ACBFS as coarse aggregate in pavement concrete located in the area that experience winter season, concrete performance not only being affected by the type of coarse aggregate it possessed, but also by the weather and the chemical deicers which were applied during the snow season. It has been reported that the application of deicers
4 on pavement concrete has affected the performance of the pavement through mechanical and chemical mechanisms [11]–[13], [15]–[17]. The motivation in pursuing a more eco-friendly concrete to address the concerns related to the environmental issues regarding concrete and cement industries, as well as answering the challenges on the application of ACBFS on pavement concrete exposed to different deicers has been the backbone of this scientific study.
1.2
Research Objectives and General Hypothesis
The previous section highlighted the challenges, which drove the motivation of this study. In order to accomplish the purposes of the study, several objectives are identified for the present study: -
to differentiate the properties of air-cooled blast furnace slag (ACBFS) with respect to natural dolomite
-
to investigate the potential of air-cooled blast furnace slag (ACBFS) as coarse aggregate in pavement concrete application
-
to investigate the impact of slag aggregate on mechanical and durability properties of pavement concrete under exposure to different type of deicers, subjecting the specimens to freezing-thawing (FT) and wetting-drying (WD) conditions
-
to study the impact of class C fly ash (FA), slag cement (SC) and the combination of both (FA+SC) on concrete properties while being subjected to different deicers and both freezing-thawing (FT) and wetting-drying (WD) cycles
-
to investigate the impact of different type of deicers on the mechanical and durability properties of pavement concrete made with ACBFS as coarse aggregate
-
to investigate the effect of deicers on the hydration products in concrete matrix
-
to investigate the effect of freezing-thawing and wetting-drying exposure on concrete durability
5 In addition to the objectives derived in this study, several hypotheses are proposed for the present study. These hypotheses are as follows: -
Disregard the differences in terms of aggregate properties, with respect to natural aggregate, air-cooled blast furnace slag (ACBFS) is a viable option for coarse aggregate in pavement concrete.
-
Air-cooled blast furnace slag may have lower specific gravity, higher absorption and higher sulfate content than that of the natural aggregate.
-
The application of chemical deicers on pavement concrete affects the performance of the concrete through mechanical and chemical mechanisms, which tends to accelerate concrete’s deterioration.
-
The performance of concrete is affected by the surrounding condition (i.e. temperature and moisture).
-
The application of fly ash and slag cement as partial cement replacement improve concrete’s performance.
1.3
Scope of the Research
This study covers the evaluation of the influence of multiple aspects (i.e. aggregate, binder system, deicers and exposure condition) to concrete properties. A total of eight different concrete mixtures were produced in this study following Indiana Department Transportation (INDOT) specification and standard for pavement concrete [18]. The mixtures were prepared using two types of coarse aggregates, ACBFS and dolomite. Four different binder systems were used, included the following: (a) plain – 100% portland cement (PC), two types of binary binder systems (b) 20% fly ash (FA) + 80% PC and (c) 25% slag cement (SC) + 75% PC, and a ternary system (d) 17% FA + 23% SC + 60% PC. More details regarding the scope of the current study is as follows: -
The evaluation and comparison of several properties of ACBFS and dolomite aggregates
-
The evaluation, analysis and comparison of concrete’s properties made with two different types of coarse aggregate with different binder systems (plain, binary
6 and ternary) exposed to several types of chloride-based deicing chemical (NaCl, MgCl2 and CaCl2) while subjected to freezing-thawing (FT) and wetting-drying (WD) conditions. -
The determination and analysis of chloride ingress (i.e. chloride penetration depth) on concrete specimens after being exposed for a test period to deicers while subjected to either freezing-thawing (FT) or wetting-drying (WD) conditions.
-
The observation and analysis of the physical changes of concrete specimens at different periods of time during the exposure to either deicers or distilled water while subjected to either freezing-thawing (FT) or wetting-drying (WD) conditions.
-
The evaluation of concrete’s matrix at microscopic level to analyze the effect of ACBFS as coarse aggregate, as well as the effect of different binder systems in concrete.
-
The microscopic evaluation and analysis of concrete matrix exposed to either deicers or distilled water while subjected to either freezing-thawing (FT) or wetting-drying (WD) conditions.
-
Statistical analysis of several experimental results to assess the significance of different factors (type of coarse aggregate, type of binder, type of deicer and type of exposure condition) and to distinguish the impact among different levels within each factor.
1.4
Organization of the Thesis
The thesis will be composed of six chapters. Chapter 1 consists of an introduction to the study, the background of the study, research objectives and general hypotheses regarding topics, which are related with the study. In addition, Chapter 1 also includes the scope of the research and the organization of the manuscript. Chapter 2 contains literature review of the past studies regarding the physical characteristic and chemical properties of air-cooled blast furnace slag (ACBFS) and the influence of ACBFS to concrete when it’s
7 applied as coarse aggregate in concrete’s system. Chapter 2 also provides scientific information of the cementitious materials (slag cement and fly ash) used in this study along with their influences to concrete. The mechanical and chemical mechanisms of the three types of deicers (i.e. NaCl, MgCl2 and CaCl2) in influencing concrete’s performance were also presented in Chapter 2. Chapter 3 presents the information about materials used in the study, consist of concrete making materials (i.e. binders and aggregates) and the deicers (NaCl, MgCl2 and CaCl2). The selection of exposure conditions is also discussed in Chapter 3. Moreover, Chapter 3 presents the mixture designs, mixing procedure and the experimental plan or test matrix. The test matrix consists of two different main tests based on the subject of the test, aggregate test and test on concrete (both plastic and hardened phases). Chapter 4 covers the experimental results, discussion and analysis for each of the experimental test conducted in this study. The analysis of several tested parameters involved statistical analysis, which results were discussed and presented in Chapter 4. In addition, the microscopic analysis results using scanning electron microscopy (SEM) and the discussion were covered in Chapter 4. Chapter 5 contains summary of the study based on the results and discussion presented in Chapter 4. Chapter 6 presents conclusions of the overall study and the recommendations for the application of air-cooled blast furnace slag (ACBFS) in commercial concrete.
8
CHAPTER 2. LITERATURE REVIEW
2.1
Introduction
A review of the literature related to the materials used in this study, i.e. ACBFS coarse aggregate, fly ash, slag cement and deicers are discussed in this chapter. This chapter also provides the information regarding the effect of the aforementioned materials to concrete properties.
2.2
Air-Cooled Blast Furnace Slag (ACBFS)
Slag is a byproduct of metallurgical operations, and typically contains gangue from the metal ore, flux material and unburned fuel constituents [14]. The ACBFS is categorized as ferrous slag as it is derived from the production of pig iron.
2.2.1
Properties of Air-Cooled Blast Furnace Slag
The four major oxide phases typically present in ACBFS include: CaO, SiO2, Al2O3 and MgO [14]. These oxides account for approximately 95% of ACBFS composition (see Table 2-1) with the remaining 5% consisting of sulfur, manganese, iron, titanium, fluorine, sodium and potassium oxides.
9 Table 2-1. Typical composition of ACBFS [14]. Component Major components Lime (CaO) Silica (SiO2)
Percentage 95 30-40 28-42
Alumina (Al2O3) Magnesia (MgO) Minor components Sulfur (CaS, other sulphides, sulfates) Iron (FeO, Fe2O3) Manganese (MnO) Rare components Na2O + K2O
5-22 5-15 5 1-2 0.3-1.7 0.2-1 0-1
TiO2
0-1
V2 O5
0-1
Cr2O3
0-1
The individual ACBFS particles are porous. The variability in specific gravity and absorption of ACBFS also depends on the particle size as illustrated in Figure 2-1.
Absorption (%)
2.8 2.7 2.6 2.5 2.4 2.3 2.2 2.1 2.0
4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0.0 0
0.2
0.4
0.6
0.8
1
Absorption (%)
Bulk Specific Gravity
Bulk Specific Gravity
1.2
Particle size (in)
Figure 2-1. Relationship between absorption, bulk specific gravity, and ACBFS particle size (Edw. C. Levy Company 2010) [14]. Chesner et al. [19] had reported that ACBFS aggregate typically has a high angle of friction (40 to 45 degrees). The L.A. abrasion values of ACBFS aggregate range
10 between 35% to 45%, its hardness ranges from 5 to 6 (Mohs scale) and the California bearing ratio (CBR) is typically greater than 100 due to its angular shape and rough texture [14]. The typical compacted unit weight of ACBFS (measured according to ASTM C 33 [20]) ranges between 70 and 85 lb/ft3 [14]. By comparison, the compacted unit weight of lightweight aggregates typically ranges between 55 and 70 lb/ft3, while that of normal weight aggregates typically ranges between 75 and 110 lb/ft3. Some states (e. q. Illinois, Pennsylvania and Kentucky) require that the compacted unit weight of ACBFS should not be lower than 70 lb/ft3 when it is used in pavement concrete [21]– [23]. Slowly cooled slag will have fewer entrapped pores and higher degree of crystallinity, which is more desirable for ACBFS aggregates [14]. The absorption of ACBFS coarse aggregate is normally higher (about 1% to 8%) than that of the natural aggregate (about 0.5% to 3%). For use as an aggregate in pavement concrete, the ACBFS with higher density (>2.4) and lower absorption (less than 4%) is more desirable [14].
2.2.2
Influence of Chemical Properties of Air-Cooled Blast Furnace Slag on Concrete
Two chemical properties of ACBFS that are of concern with respect to the use of this material as coarse aggregate in concrete include iron unsoundness and dicalcium silicate unsoundness [14]. Iron unsoundness becomes a problem only if partially reduced iron oxides in the slag undergo additional oxidation, as this process results in expansive reaction and leads to disintegration of the ACBFS particles [14]. Testing for iron unsoundness involves immersing pieces of slag in water for a period of 14 days and observing whether any of the particles crack or disintegrate. The dicalcium silicate unsoundness is caused by an increase in volume of the CaO-SiO2 (C2S) phase as a result of its inversion from beta form to gamma form during cooling. That volume expansion will damage the ACBFS aggregate particles in a process commonly referred to as falling [14]. Fortunately, this disruptive transformation process occurs only during the cooling process (in the temperature range from 7500F to 9300F (4000C to 5000C)) and thus it is effectively completed within a few days as the slag reaches ambient temperature [24].
11 The presence of calcium sulfide (oldhamite (CaS)) in ACBFS (the result of the sulfur from the coke fuel reacting with calcium from the dolomite or limestone used as flux during iron production), also presents a concern with respect to the application of ACBFS in the concrete. In highly alkaline condition (pH>13), typical of most concretes, calcium sulfide is highly soluble and will not be present as an equilibrium phase. The dissolution of calcium sulfide increases the opportunity for calcium sulfide to hydrate, which can contribute to volume instability when it is present in substantial amounts [25]. The hydration process of calcium sulfide progresses according to Equation 2-1 shown below [26]:
CaS + H2O + CO2
H2S + CaSO4 + CaCO2 + S
Equation 2-1
Once formed, calcium sulfate (CaSO4) can further react with the existing monosulfate (4CaO, Al2O3·SO3·12H2O) to produce ettringite (6CaO·Al2O3·SO3 ·32H2O) as shown in Equation 2-2 [27]. 4CaO·Al2O3·SO3·12H2O + 2Ca2+ + SO42- + 24H2O 6CaO·Al2O3·SO3·32H2O
Equation 2-2
Unlike sulfate attack, which occurs in the presence of alkali sulfates and involves the decalcification of C-S-H, no decalcification of C-S-H takes place in the process shown in Eq. 2-1 and 2-2 since all the calcium ions are supplied by calcium sulfate. As such, the integrity of the hydrated cement phases remain unaffected [14]. The ettringite produced during reaction shown in Eq. 2-2 fills the air void system. This process may initially lead to the strength increase, but it may also compromise the effectiveness of the air-void system with respect to freeze-thaw protection. The addition of limestone (CaCO3) to Portland cement provides carbonate, which is required for thaumasite formation. Several researchers have found that relatively high sulfate levels combined with alkaline conditions leads to the formation of thaumasite [27]–[30]. Both of these conditions may exist in concrete made with high-alkali cement and ACBFS, and the potential for thaumasite-related distress increases as the limestone
12 content of cement increases [14]. Thaumasite formation reduces the binding capacity of hydrated cement in the hardened concrete and causes loss of strength. The expansive disruption that is normally associated with sulfate attack sometimes accompanies the formation of thaumasite, but is not a dominating feature [31]. To address the potentially adverse effects of calcium sulfide present in ACBFS, the British Standard Institute limits the sulfur content of concrete to maximum of approximately 2% by weight [14]. The Organization for Economic Co-operation and Development (OECD) has published a report which states that ACBFS must have a total sulfur content of less than 2% and a sulfate content of less than 0.7% in order for it to be used as concrete aggregate [32].
2.2.3
Influence of Mechanical Properties of Air-Cooled Blast Furnace Slag on Concrete
Since, as already mentioned, the properties of ACBFS are significantly different from those of natural aggregates, they influence both, the fresh and hardened properties of concrete. In terms of fresh concrete properties, the highly porous microstructure of ACBFS, combined with higher angularity/surface area than that characteristic of natural aggregate, lead to the need for additional mortar (cementitious material, water and sand) to maintain the workability. If ACBFS is batched dry during concrete production, the mixture may undergo premature stiffening and may develop early-age cracking as water is absorbed from the paste by the aggregate. In order to avoid these negative developments, the ACBFS should be batched in water-saturated condition. This requires the contractor to keep the stockpiles wet, which results in extra level of stockpile management that is not necessarily required when only natural aggregates are used [14]. In terms of hardened concrete properties, concrete made with ACBFS as coarse aggregate was reported to posses acceptable strength, stiffness, coefficient of thermal expansion (CTE) and wear resistance for usage in concrete pavements [14]. However, the issue of freeze-thaw resistance of concrete made with ACBFS coarse aggregate still remains unresolved [14]. The most common view is that the unique nature of the pore structure within the ACBFS aggregate should result in good performance, as the
13 aggregate will not saturate under field conditions. However, based on their laboratory study and field investigation, the Michigan Department of Transportation (MDOT) maintains that freeze-thaw durability of paving concrete made with ACBFS is compromised [14].
2.3
Slag Cement/Ground Granulated Blast Furnace Slag (GGBFS)
Slag cement, or also known as ground granulated blast-furnace slag (GGBFS), is a hydraulic cement formed when granulated blast-furnace slag is ground to a suitable fineness [33]. The typical slag cement includes following oxides: lime (CaO), silica (SiO2), alumina (Al2O3) and magnesia (MgO). Minor amounts of the other oxides, such as SO3, FeO or Fe2O3, TiO2, K2O, and Na2O also be found the slag cement [34]. Unlike ordinary portland cement (OPC) which immediately reacts with water, slag cement reacts with water at a slower rate and it is normally mixed with activators [34], [35]. Some most commonly used activators for slag cement are sulfates, portland cement, sodium silicate, calcium hydroxide and caustic soda (NaOH). Most of these activators are called alkali activators as they are dominantly consist of alkali (e.g. Li, Na, K).
2.3.1
Hydration Products of Slag Cement
Similar to portland cement (OPC), the dominant hydration product of slag cement is C-S-H [36], [37] with C/S ratio lower than that of C-S-H from the normal OPC hydration [34]. The other hydration products of slag cement are hydrotalcite, Fe-rich hydrogarnet phase, ettringite and monosulfate. The hydration rate of slag cement is reported to be comparable to C2S present in OPC [34]. However, it can differ greatly from one slag to another due to the different in the reactivity of the material. Slag cement reactivity depends on its oxide composition, presence of crystalline minerals, glass structure and pH value of the environment [34]. The activation energy of slag cement (50-59 kJ/mol) is found to be higher than that of portland cement (~40 kJ/mol) [38], indicating that slag cement is less reactive than OPC.
14 2.3.2
Properties of Concrete Containing Slag Cement
The different properties of concrete containing mixture of the OPC and slag cement are briefly discussed in the next sub-chapters.
2.3.2.1 Fresh Concrete Properties
Compared to the normal concrete (concrete with OPC), concrete containing slag cement has higher workability as its less reactive behavior has led to the longer setting time. The increase in slag content from 35% to 65% (of partial OPC replacement) had increased the initial setting time by 60 minutes [34]. The bleeding rate of concrete is dictated by the ratio of the surface area of solid to the unit volume of the water. Thus, the particle size of slag cement will drive this behavior in concrete containing slag cement. If the particle size of the slag cement is finer than the particle size of OPC, then it is expected that partial substitution of OPC with slag cement will reduce the bleeding of the overall concrete [34].
2.3.2.2 Strength Development
The strength of concrete with slag cement at early age (< 14 days) is generally lower than that of normal concrete. However, at later age (> 28 days), the compressive strength of slag cement concrete (with 40%-65% of portland cement replacement levels) was found to be higher than the compressive strength of normal concrete [34], [37]. It’s also been reported that the strength development of slag cement concrete is more sensitive to the curing temperature than the rate of strength development of normal concrete [34].
15 2.3.2.3 Durability
Some durability aspects of concrete containing slag cement are discussed in this sub-chapter, including alkali-silica reactivity, sulfate resistance and permeability.
Alkali-silica Reactivity
The use of slag cement as partial replacement of OPC reduces the potential of reaction between some siliceous components of concrete aggregates and the alkalis since slag cement contains less alkali than OPC and thus replacing OPC with slag cement results in the dilution effect. The slower reaction of slag cement in general, compared to OPC in the hydration process also contributes to minimize the risk of alkali-silica reaction [34], [39]. In addition, the reaction products of slag cement with portland cement clinker have higher potentials for binding alkalis (for more details, see Chapter 5 of reference [34]) thus immobilizing them within the solid product and thus lowering the pH value of the pore solution.
Sulfate Resistance
The addition of slag cement as partial OPC replacement reduces the risk of sulfate attack [34], [40]. The possible explanations are as follows: •
The addition of slag cement in concrete dilutes the total amount of C3A (since slag cement does not contain C3A).
•
Slag cement concrete has denser matrix, and thus lower permeability, due to the additional C-S-H formed during the hydration of slag cement.
•
Slag reacts with portlandite (Ca(OH)2) to form C-S-H (more detail in Chapter 4 reference [34]). The consumption of Ca(OH)2 reduces the potential of sodium-sulfate attack.
16 Permeability
At the same w/cm, concrete containing slag cement shows denser microstructure (through the extra production of C-S-H at the expense of Ca(OH)2). Thus, it reduces the permeability of the concrete and limits the intrusion of ionic species which may harm the concrete [34], [37].
2.4
Fly Ash
Fly ash is one of the residues generated by coal combustion and is composed of fine particles. In general, fly ash composition includes substantial amount of silicon dioxide (SiO2), aluminum oxide (Al2O3) and calcium oxide (CaO) [14]. ASTM C 618 [41] classifies fly ash into three types, class N, class F and class C. The classification based on their origin, chemical composition and physical characteristics.
2.4.1
Pozzolanic Reaction of Fly Ash
Fly ash reacts with calcium hydroxide available in concrete, forming additional cementitious compound inside concrete’s matrix as presented in Equation 2-3 [42].
Ca(OH)2 + (calcium hydroxide)
SiO2 (silica)
C-S-H Equation 2-3 [42] (calcium silicate hydrate)
As indicated in Equation 2-3, in order to produce C-S-H, the hydration of OPC should occur prior to the pozzolanic reaction which involves silica from fly ash reacting with the hydration product of OPC, which is Ca(OH)2. 2.4.2
Properties of Concrete Containing Fly Ash
The additional C-S-H formed during pozzolanic reaction (Equation 2-3) densifies the concrete’s matrix. This densification, however, occurs at later age since, as explained
17 previously, the pozzolanic reaction takes place after the initial hydration of OPC. In fresh concrete, the fly ash increases the setting time and the workability of concrete [43]. At early age (
