Evaluation of metakaolin for GDOT concrete specifications (ASTM C 618 N Pozzolan) and mass concrete provision

GEORGIA DOT RESEARCH PROJECT 16-30 FINAL REPORT
Phase II Evaluation of Metakaolin for GDOT Concrete Specifications (ASTM C618 N Pozzolan) and
Mass Concrete Provision
OFFICE OF PERFORMANCE-BASED MANAGEMENT AND RESEARCH 600 W. PEACHTREE ST. NW ATLANTA, GA 30308

1. Report No.:

2. Government Accession No.: 3. Recipient's Catalog No.:

FHWA-GA-19-1630

4. Title and Subtitle:
Phase II Evaluation of Metakaolin for GDOT Concrete
Specifications (ASTM C618 N Pozzolan) and Mass
Concrete Provision
7. Author(s): Mi G. Chorzepa, Ph.D., P.E., Stephan A. Durham Ph.D., P.E., and Hiwa Hamid
9. Performing Organization Name and Address: University of Georgia College of Engineering Driftmier Engineering Center, Athens, GA 30602 Phone: (706) 357-0038 Email: chorzepa@uga.edu
12. Sponsoring Agency Name and Address: Georgia Department of Transportation Office of Performance-Based Management and Research 600 W. Peachtree St. NW Atlanta, GA 30308
15. Supplementary Notes:

5. Report Date: November 2019
6. Performing Organization Code:
8. Performing Organization Report No.: 16-30
10. Work Unit No.:
11. Contract or Grant No.: PI#
13. Type of Report and Period Covered: Final; August 2016-November 2019
14. Sponsoring Agency Code:

Prepared in cooperation with the U.S. Department of Transportation, Federal Highway Administration.

16. Abstract: This report includes both experimental and analytical investigations of concrete mixtures

containing supplementary cementitious materials to identify sustainable alternatives to Class F fly ash for use

in Georgia's mass concrete structures. The primary goal of this study is to identify concrete mixtures that reduce

the potential for thermal cracking caused by the heat of hydration of cementitious materials in order to optimize

long-term performance of massive concrete structures. Through this study, the research team has identified

ternary replacement mixtures potentially suitable for mass concrete placements. Additionally, the team has

developed temperature prediction models based on a coupled thermal-structural analysis to aid in maximum

temperature and temperature differential predictions. Among the 45% cement replacement mixtures considered

in this study, the ternary mixture with 30% slag and 15% metakaolin replacements achieves superior

performance in terms of mechanical properties, durability, and thermal cracking potential from heat of

hydration. The research team recommends that GDOT consider changes to the Special Provisions to Section

500 (see Appendix A) and further study the performance of two ternary mixtures containing a 70% cement

replacement with 1) 40% slag + 30% fly ash and 2) 55% slag + 15% metakaolin in order to reduce the potential

for thermal cracking, which undermines the durability of mass concrete structures in Georgia.

17. Keywords:

18. Distribution Statement:

Metakoalin, Slag Cement, Fly Ash, Heat

of Hydration, Mass Concrete, Bridge

Seal, Temperature, Temperature

Differential, Binary, Ternary Mixture

19. Security

20. Security Classification (of this 21. No. of Pages: 22. Price:

Classification

page):

347

(of this report):

Unclassified

Unclassified

Form DOT 1700.7 (8-69)

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GDOT Research Project 16-30 Phase II Evaluation of Metakaolin for GDOT Concrete Specifications (ASTM C
618 N Pozzolan) and Mass Concrete Provision Final Report By
Mi G. Chorzepa, Ph.D., P.E. Associate Professor of Civil Engineering
Stephan A. Durham, Ph.D., P.E. Professor of Civil Engineering
Hiwa Hamid Ph.D. Candidate University of Georgia College of Engineering
Contract with Georgia Department of Transportation
In cooperation with U.S. Department of Transportation Federal Highway Administration
November 2019
The contents of this report reflect the views of the authors, who are responsible for the facts and accuracy of the data presented herein. The contents do not necessarily reflect the official views of the Georgia Department of Transportation or the Federal Highway Administration. This report does not constitute a standard, specification, or regulation.
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TABLE OF CONTENTS
Page TABLE OF CONTENTS ................................................................................................ iv LIST OF TABLES ............................................................................................................ x LIST OF FIGURES ........................................................................................................ xii EXECUTIVE SUMMARY .......................................................................................... xxii ACKNOWLEDGEMENTS ........................................................................................ xxiv 1. INTRODUCTION ........................................................................................................ 1
BACKGROUND .............................................................................................................. 1 Concrete Behavior and Elevated Temperature .................................................................... 1 Simple facts about thermal loading and concrete behavior ............................................. 1 Temperature increase or decrease.................................................................................... 3 Uniform temperature increase and gradient temperature................................................. 3 Behavior of concrete members ........................................................................................ 5 Thermal stress and restraints............................................................................................ 6 Supplementary Cementitious Materials............................................................................... 7
PROBLEM STATEMENT ............................................................................................... 11 RESEARCH OBJECTIVES .............................................................................................. 13 RESEARCH SIGNIFICANCE AND SCOPE ........................................................................ 13 RESEARCH METHODOLOGY........................................................................................ 14
Task 1. Perform Extensive Literature Review................................................................... 14 Task 2. Design, Batch, and Test Concrete Mixtures with Three Metakaolin Products ..... 14 Task 3. Design, Construct, and Quantify Temperature Rise in Mass Concrete ................ 14
Task 3.1 - Design test procedures for mass concrete mixtures ...................................... 14 Task 3.2 Construct cube molds and specimens .......................................................... 15 Task 3.3 Internal temperature monitoring in test specimens ...................................... 16 Task 4. Evaluation of Maximum Temperature Limits ...................................................... 16 Task 4.1 Thermal and structural modeling ................................................................. 16 Task 4.2 Design and construct test specimens ............................................................ 16 Task 4.3 Evaluation of temperature limits .................................................................. 17 Task 5. Data Analysis and Synthesis of Findings.............................................................. 18 IMPLEMENTATION ...................................................................................................... 18
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ORGANIZATION OF THE REPORT ................................................................................. 18 2. COMPARISON OF BINARY AND TERNARY MIXTURES .............................. 21
PRELIMINARY INVESTIGATION INTO HEAT OF CEMENTITIOUS MATERIAL HYDRATION . ................................................................................................................................... 21
Experimental Design ......................................................................................................... 21 Results ............................................................................................................................... 23
Heat of hydration in binary mixtures including metakaolin .......................................... 23 Heat of hydration of ternary and other binary replacement mixtures ............................ 25 Heat of hydration of ternary mixtures with various percentages of slag and metakaolin .. ....................................................................................................................................... 27 Analysis of Results ............................................................................................................ 29 Effect of metakaolin binary mixture on heat of hydration............................................. 29 Effect of binary mixtures containing fly ash and slag on heat of hydration .................. 30 Effect of ternary mixtures on heat of hydration............................................................. 30 Estimating the Heat Generated from Pozzolanic Materials ............................................... 32 Estimated heat of hydration in binary mixtures including metakaolin .......................... 34 Estimated heat of hydration in ternary and alternate binary mixtures ........................... 34 MECHANICAL PROPERTIES AND DURABILITY RESULTS.............................................. 35 Fresh Properties ................................................................................................................. 38 Binary Metakaolin Hardened Properties............................................................................ 39 Mechanical properties.................................................................................................... 39 Durability ....................................................................................................................... 43 Dimensional stability ..................................................................................................... 46 Ternary and Alternate Binary SCM Hardened Properties ................................................. 48 Mechanical properties.................................................................................................... 48 Durability ....................................................................................................................... 52 Dimensional stability ..................................................................................................... 54 DISCUSSION................................................................................................................ 56 Comparison of Binary Metakaolin Mixtures ..................................................................... 56 Comparison of Ternary and Alternate Binary SCM Mixtures........................................... 61 CONCLUSIONS AND RECOMMENDATIONS FROM SECTION 2 ........................................ 64 Summary of Findings ........................................................................................................ 65 Recommendations for Usage ............................................................................................. 67
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Future Work....................................................................................................................... 68 3. EXPERIMENTAL INVESTIGATION OF THE HEAT OF HYDRATION AND
TEMPERATURE CHANGES .................................................................................. 70 LITERATURE REVIEW ................................................................................................. 70 U.S. Mass Concrete Specifications and Guides................................................................. 70 American Concrete Institute specifications for structural concrete (ACI 301-16) ........ 70 ACI guide to mass concrete (ACI 207.1R) .................................................................... 73 ACI technical report on mass concrete (ACI 207.2R) ................................................... 74 AASHTO and FHWA construction specifications ........................................................ 75 U.S. State DOTs Mass Concrete Specifications ................................................................ 76 Thermally Induced Cracking ............................................................................................. 97 Thermal gradient............................................................................................................ 98 Degree of thermal restraints......................................................................................... 100 PROCEDURES FOR QUANTIFYING TEMPERATURES.................................................... 102 Introduction ..................................................................................................................... 102 General background and motivation............................................................................ 102 Study objectives........................................................................................................... 105 Scope of experimental study........................................................................................ 105 Experimental Investigation .............................................................................................. 106 Materials ...................................................................................................................... 106 Design and testing for parts 1 and 2 mixtures.............................................................. 108 Design of mass concrete specimens............................................................................. 113 Insulation material for mass concrete specimens......................................................... 115 RESULTS................................................................................................................... 117 Part 1 Results: Calorimetry of Paste and Mortar Specimens ........................................... 118 Effect of SCMs and replacement levels on heat of hydration of paste specimens ...... 118 Effect of PVA and BaO addition on heat of hydration ................................................ 118 Effect of SCMs and replacement levels on heat of hydration of mortar specimens .... 120 Part 2 Results: Temperature Rise Measurements from Concrete Cube Specimens ........ 121 Effect of summer and winter placements on temperature rise..................................... 122 Temperature rise of binary and ternary replacement mixtures .................................... 122 ANALYSIS OF THE RESULTS ...................................................................................... 123 Analysis of Results from Part 1 Mixtures........................................................................ 123
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Effect of SCMs on heat of hydration from paste and sampled mortar mixtures.......... 123 Heat of hydration from paste and sampled mortar mixtures........................................ 124 The heat of hydration of PVA and BaO mixtures........................................................ 125 Analysis of Results from Part 2 Mixtures........................................................................ 129 Effect of placement temperature on temperature rise .................................................. 129 Effect of SCMs on temperature rise from cube specimens.......................................... 129 Effect of SCMs on time and duration of the maximum temperature........................... 131 Efficiency of temperature measurements from mock-up specimens ........................... 133 Comparison between heat of hydration and temperature rise results .......................... 135 Part 3 Comparison with Available Equations to Predict Maximum Temperature Rise 139 CONCLUSIONS .......................................................................................................... 144 Findings from Part 1 ........................................................................................................ 144 Findings from Part 2 ........................................................................................................ 145 Findings from Part 3 ........................................................................................................ 146 DISCUSSION.............................................................................................................. 146 4. ANALYTICAL INVESTIGATION OF MASS CONCRETE STRUCTURES . 147 MOTIVATION, BACKGROUND, AND PROCEDURE....................................................... 147 Motivation ....................................................................................................................... 147 Background...................................................................................................................... 148 Research Procedure ......................................................................................................... 148 MATERIAL PROPERTIES AND MODELS ...................................................................... 150 Thermal Properties........................................................................................................... 150 Thermal conductivity................................................................................................... 150 Specific heat................................................................................................................. 155 Mechanical Properties ..................................................................................................... 156 Material Models............................................................................................................... 157 ELEMENT TYPES....................................................................................................... 158 BOUNDARY CONDITIONS .......................................................................................... 160 DEVELOPMENT OF TEMPERATURE INPUT DATA ....................................................... 160 COUPLED THERMAL-STRUCTURAL ANALYSIS .......................................................... 161 VALIDATION EXPERIMENTAL RESULTS FROM CUBE SPECIMENS ........................... 162 FEA Model Description................................................................................................... 162 Boundary Condition......................................................................................................... 167
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Temperature Results ........................................................................................................ 167 Adjustment of Specific Heat Capacity............................................................................. 172 VALIDATION EXPERIMENTAL RESULTS FROM A LARGER CONCRETE SPECIMEN ... 177 FEA Model Description................................................................................................... 177 Boundary Conditions ....................................................................................................... 181 Temperature Results ........................................................................................................ 182 Strain Results ................................................................................................................... 183 Conclusions ..................................................................................................................... 185 CASE STUDY A BRIDGE SEAL STRUCTURE ............................................................ 186 Background and Model Description ................................................................................ 186 Heat of Hydration Input................................................................................................... 192 Boundary Conditions ....................................................................................................... 194 Temperature Results ........................................................................................................ 195
Summer placement condition ...................................................................................... 195 Winter placement condition......................................................................................... 203 Strain Results ................................................................................................................... 210 Summer placement condition ...................................................................................... 210 Winter placement condition......................................................................................... 215 Validation of Bridge Seal Temperature ........................................................................... 221 Analysis of Results and Discussion ................................................................................. 222 5. SENSITIVITY ANALYSES ON VOLUME-TO-SURFACE AREA RATIOS AND MIXTURE DESIGNS .................................................................................... 225 FOUNDATION MODEL ............................................................................................... 226 Sensitivity of Volume-to-Surface Area Ratios ................................................................ 226 Sensitivity of Mixture Designs ........................................................................................ 231 Total Strain versus V/A ratio ........................................................................................... 234 Sensitivity of Slag Replacement Level ............................................................................ 235 Sensitivity of Ternary Mixtures at 70% Replacement Level........................................... 237 Sensitivity of Water-to-Cementitious Material Ratios .................................................... 240 Sensitivity of Insulation Material R-value....................................................................... 242 Summary of Sensitivity Analysis for Foundation............................................................ 245 COLUMN MODEL ...................................................................................................... 247 Sensitivity of Volume-to-Surface Area Ratios ................................................................ 247
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Sensitivity of Mixture Designs ........................................................................................ 251 Sensitivity of Slag Replacement Level ............................................................................ 251 Sensitivity of Ternary Mixtures at 70% Replacement Level........................................... 258 Sensitivity of Water-to-Cementitious Material Ratios .................................................... 258 Sensitivity of Insulation Materials by R-value ................................................................ 261 Summary of Sensitivity Analysis for Column ................................................................. 265 DISCUSSION ON THE BRIDGE SEAL MODEL .............................................................. 267 FINDINGS AND DISCUSSION ...................................................................................... 273 6. CONCLUSIONS....................................................................................................... 275 SUPPLEMENTARY CEMENTITIOUS MATERIALS ......................................................... 275 HEAT OF HYDRATION IN CEMENTITIOUS MATERIALS AND TEMPERATURE .............. 278 ANALYTICAL INVESTIGATION .................................................................................. 279 7. RECOMMENDATIONS AND FUTURE WORK ................................................ 282 RECOMMENDATIONS FROM THE PHASE-I AND PHASE-II TESTS INVOLVING MK....... 282 RECOMMENDATION FROM THE PHASE-II MASS CONCRETE STUDY............................ 282 TOWARDS PERFORMANCE-BASED SPECIFICATIONS .................................................. 285 IMPLEMENTABLE RECOMMENDATIONS .................................................................... 286 REFERENCES.............................................................................................................. 287 APPENDIX A CHANGES RECOMMENDED TO CURRENT SPECIAL
PROVISION ..................................................................................... 300 APPENDIX B BASIS FOR RECOMMENDATIONS SHOWN IN APPENDIX A ..
............................................................................................................ 307 APPENDIX C OTHER RECOMMENDATIONS FROM STATE DOT REVIEW .
........................................................................................................... 316 APPENDIX D BRIDGE SEAL ANALYSIS WITH A RECTANGULAR
COLUMN.......................................................................................... 328 APPENDIX E VALIDATION OF STRAIN FROM GRADIENT
TEMPERATURE ............................................................................. 337
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LIST OF TABLES

Table No.

Page

Table 1 Maximum allowable internal and differential temperature limits. ................... 17 Table 2 Mixtures used for HoH testing.......................................................................... 22 Table 3 Percent reduction in HoH in binary and ternary mixtures. ............................... 23 Table 4 Oxide ratios for select 45% replacements......................................................... 31 Table 5 Summary of binary MK performance............................................................... 36 Table 6 Summary of alternate binary and ternary SCM performance. .......................... 37 Table 7 Fresh concrete properties of mixtures............................................................... 38 Table 8 State DOTs that publish mass concrete specifications. .................................... 78 Table 9 Mass concrete document type by state DOT. ................................................... 79 Table 10 Mass concrete definition by state DOT. ......................................................... 81 Table 11 Temperature limit requirements by state DOT. .............................................. 82 Table 12 Maximum concrete placement temperature requirements by state DOT. ...... 84 Table 13 Minimum and maximum SCM content requirements by state DOT.............. 86 Table 14 Fly ash and slag replacement content requirements by state DOT................. 87 Table 15 Ternary replacement and other SCM limits by state DOT. ............................ 89 Table 16 Strength and heat generation criteria by state DOT........................................ 90 Table 17 Water-to-cementitious material ratio and slump by state DOT. ..................... 91 Table 18 Curing period requirements by state DOT...................................................... 93 Table 19 Formwork removal time requirements by state DOT. .................................... 94 Table 20 Methods to cool down concrete temperature by state DOT. .......................... 95 Table 21 Temperature monitoring requirements by state DOT..................................... 97 Table 22 Chemical composition and physical properties of cementitious materials. .. 107 Table 23 Concrete mixture proportions, lb/yd3 (1 lb/yd3 = 0.5933 kg/m3)................. 109 Table 24 Paste mixture proportions for HoH testing (gram). ...................................... 112 Table 25 Proportions of PVA and BaO in paste mixtures for HoH testing (gram). .... 113 Table 26 Properties of the Kooltherm K20 Concrete Sandwich Board Insulation
(Kingspan USA, 2019).................................................................................. 117 Table 27 Time of maximum temperature occurrence and its maintained duration. .... 132

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Table 28 Maximum temperature rise comparisons, F (C). ....................................... 142 Table 29 Thermal properties of mass concrete mixtures (ACI 207.2R-07, 2007). ..... 153 Table 30 Typical thermal conductivity values for concrete selected by type of aggregate
(U.S. Bureau of Reclamation 1940) (ACI 207.2R-07, 2007). ...................... 154 Table 31 Thermal conductivity of common formwork and insulation materials. ....... 154 Table 32 Specific heat value of concrete ingredients (ASTM C1702, 2017). ............. 156 Table 33 Unit weight and calculated specific heat values for concrete mixtures
containing different SCMs. ........................................................................... 165 Table 34 Adjusted specific heat capacities used for analysis. ..................................... 173 Table 35 Mixture proportion for the large specimens (Jung et al., 2017). .................. 179 Table 36 Mixture proportion used in the bridge seal, lb/yd3 (kg/m3). ......................... 192 Table 37 Thermal and mechanical properties of the seal concrete. ............................. 192 Table 38 Maximum temperature rise comparisons, F (C). ....................................... 221 Table 39 Parameters considered in the sensitivity analysis. ........................................ 226 Table 40 Summary of results for the foundation at V/A=3.0 (summer)...................... 245 Table 41 Summary of results for the foundation at V/A=3.0 (winter). ....................... 246 Table 42 Summary of results for the column at V/A=3.0 (summer). .......................... 266 Table 43 Summary of results for the column at V/A=3.0 (winter).............................. 266 Table 44 Summary of Analysis Results - Bridge Seal (summer placement)............... 272 Table 45 Summary of Analysis Results - Bridge Seal (winter placement). ................ 272 Table 46 Maximum Allowable Internal and Differential Temperature. ...................... 274
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LIST OF FIGURES

Figure No.

Page

Figure 1 1D thermal expansion........................................................................................ 2 Figure 2 Temperature profile through a typical reinforced concrete section................... 3 Figure 3 Linear temperature profile. ................................................................................ 4 Figure 4 Reinforced concrete members restrained from thermal expansion and rotation.
........................................................................................................................... 6 Figure 5 Degree of restraints and thermal stresses. ......................................................... 6 Figure 6 Test layout for concrete cube placement (Gadja et al., 2014). ........................ 15 Figure 7 Kingspan Kooltherm K20 Insulation (Kingspan USA, 2019)......................... 15 Figure 8 Isothermal calorimeter used for HoH testing. ................................................. 22 Figure 9 Rate of heat flow in the Control and MK mixtures. ........................................ 24 Figure 10 HoH in the Control and MK mixtures. .......................................................... 24 Figure 11 Thermal power of the ternary and alternate binary mixtures. ....................... 26 Figure 12 HoH of the ternary and alternate binary mixtures. ........................................ 27 Figure 13 Thermal power of ternary mixtures with various percentages of slag and MK.
....................................................................................................................... 28 Figure 14 HoH of ternary mixtures with various percentages of slag and MK. ............ 28 Figure 15 Linear extrapolation of HoH for the Control mixture. .................................. 33 Figure 16 HoH generated from the pozzolanic reaction. ............................................... 33 Figure 17 Compressive strength evolution for binary MK concrete mixtures. ............. 41 Figure 18 Tension results for binary MK concrete. ....................................................... 42 Figure 19 Dynamic MOE for binary MK concrete........................................................ 42 Figure 20 RCPT results for binary MK concrete........................................................... 44 Figure 21 Sulfate expansion of binary MK mortars. ..................................................... 45 Figure 22 ASR expansion of binary MK mortars. ......................................................... 45 Figure 23 Drying shrinkage of binary MK concrete...................................................... 47 Figure 24 CTEs of binary MK concrete. ....................................................................... 47 Figure 25 Compressive strength evolution for alternate binary SCM and ternary SCM
concrete. ........................................................................................................ 50

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Figure 26 Tensile strength of alternate binary SCM and ternary SCM concrete........... 51 Figure 27 Dynamic MOEs of alternate binary SCM and ternary SCM concrete. ......... 51 Figure 28 RCPT results for alternate binary SCM and ternary SCM concrete. ............ 53 Figure 29 Sulfate expansion of alternate binary SCM and ternary SCM mortars. ........ 53 Figure 30 ASR expansion of alternate binary SCM and ternary SCM mortars............. 54 Figure 31 Drying shrinkage of alternate binary SCM and ternary SCM concrete. ....... 55 Figure 32 CTEs of alternate binary SCM and ternary SCM concrete. .......................... 56 Figure 33 Deleterious expansion by sulfate attack of MK2-10 mortar bars.................. 57 Figure 34 US states with mass concrete specifications publicly available. ................... 80 Figure 35 Temperature differential limits by state DOT. .............................................. 83 Figure 36 Concrete placement temperature limits by state DOT. ................................. 85 Figure 37 Fly ash (Class F) content limits by state DOT. ............................................. 88 Figure 38 Slag content limits by state DOT................................................................... 88 Figure 39 Water-to-cementitious material ratio recommended for mass concrete by
state DOT. ..................................................................................................... 92 Figure 40 Slump recommended by state DOT. ............................................................. 92 Figure 41 Schematic of crack development in mass concrete (Bamforth, 2007). ....... 101 Figure 42 Specimen photos and a schematic showing three parts of the study. .......... 106 Figure 43 Part 1 experimental work: HoH measurements from paste and mortar
specimens. ................................................................................................... 111 Figure 44 Part 2 experimental work: Temperature rise measurement from mass concrete
cube specimens. ........................................................................................... 114 Figure 45 Effect of SCMs and replacement levels on HoH of paste mixtures. ........... 118 Figure 46 Effect of PVA addition on HoH. ................................................................. 119 Figure 47 Effect of BaO addition on HoH................................................................... 120 Figure 48 Effect of SCMs and replacement levels on HoH of mortar mixtures.......... 121 Figure 49 Effect of placement temperature on temperature rise in the mass concrete
Control specimen......................................................................................... 122 Figure 50 Temperature rise in cube specimens............................................................ 123 Figure 51 Comparison of the effects of PVA and BaO on the HoH of Control, binary
mixtures, and ternary mixtures at seven days of hydration. ........................ 128
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Figure 52 Comparison of temperature rise between FA-30 mixture and Gadja et al. (2014) mixture. ............................................................................................ 134
Figure 53 Normalized HoH and maximum temperature rise with respect to the Control mixture......................................................................................................... 136
Figure 54 Experimental and calculated maximum temperature rise comparison. ....... 143 Figure 55 One-dimensional heat flow system (Zhao et al., 2016)............................... 151 Figure 56 Three-dimensional heat flow system (Lawrence, 2009). ............................ 152 Figure 57 CHX60 solid element in DIANA (DIANA, 2017)...................................... 158 Figure 58 Modeling reinforcing steel in a solid element (DIANA, 2017)................... 158 Figure 59 BQ4HT boundary element (DIANA, 2017). ............................................... 159 Figure 60 CQ481 interface element (DIANA, 2017). ................................................. 159 Figure 61 Geometry of the cube specimens................................................................. 162 Figure 62 Cube specimen in DIANA........................................................................... 163 Figure 63 Cube specimen interior in DIANA.............................................................. 163 Figure 64 HoH of mixtures used in the 14 cube specimens. ....................................... 164 Figure 65 Adiabatic temperature rise of mixtures used in the 14 cube specimens. ..... 166 Figure 66 Temperature distribution in a cube specimen.............................................. 168 Figure 67 Temperature rise development in cube specimens from FEA and
experimental studies using Control mixtures and calculated specific heat values........................................................................................................... 168 Figure 68 Temperature rise development in cube specimens from FEA and experimental studies using 30% binary mixtures and calculated specific heat values........................................................................................................... 169 Figure 69 Temperature rise development in cube specimens from FEA and experimental studies using 45% binary mixtures and calculated specific heat values........................................................................................................... 170 Figure 70 Temperature rise development in cube specimens from FEA and experimental studies using 45% ternary mixtures and calculated specific heat values........................................................................................................... 171
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Figure 71 Temperature rise development in cube specimens from FEA and experimental studies using Control mixtures and estimated specific heat values........................................................................................................... 173
Figure 72 Temperature rise development in cube specimens from FEA and experimental studies using 30% binary mixtures and estimated specific heat values........................................................................................................... 174
Figure 73 Temperature rise development in cube specimens from FEA and experimental studies using 45% binary mixtures and estimated specific heat values........................................................................................................... 175
Figure 74 Temperature rise development in cube specimens from FEA and experimental studies using 45% ternary mixtures and estimated specific heat values........................................................................................................... 176
Figure 75 Geometry of the 13 foot x 13 foot x 13 foot mass concrete structure (Jung et al., 2017)...................................................................................................... 178
Figure 76 HoH of the large specimen. ......................................................................... 179 Figure 77 Adiabatic temperature rise in the large specimen........................................ 180 Figure 78 The 13 foot x 13 foot x 13 foot mass concrete model in DIANA. .............. 180 Figure 79 Daily ambient temperature applied to the large cube model. ...................... 181 Figure 80 Temperature distribution in the 13 foot x 13 foot x 13 foot mass concrete
structure. ...................................................................................................... 182 Figure 81 Temperature development comparison between experimental and FEA
results in the 13 foot x 13 foot x 13 foot mass concrete element. ............... 183 Figure 82 Total strain development comparison between experimental and FEA results
at the center of the large cube specimen...................................................... 184 Figure 83 Experimental crack survey results for the 13 foot x 13 foot x 13 foot mass
concrete element. ......................................................................................... 184 Figure 84 Crack strain intensity in the large cube specimen on day 7. ....................... 185 Figure 85 View of the bridge bent (Google Maps, 2018)............................................ 186 Figure 86 Construction drawing of the bridge seal (GDOT, 2010). ............................ 187 Figure 87 Site photo of the bridge bent. ...................................................................... 188
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Figure 88 Dimensions of the seal, footing, column, and cap of the bridge bent structure. ..................................................................................................................... 189
Figure 89 Construction phases of the bridge bent. ...................................................... 190 Figure 90 Bridge bent model in DIANA. .................................................................... 191 Figure 91 Rebar arrangement in the bridge seal model. .............................................. 191 Figure 92 HoH of the bridge seal mixture. .................................................................. 193 Figure 93 Adiabatic temperature rise of the bridge seal concrete mixture. ................. 193 Figure 94 Summer and winter daily ambient and water temperatures used for analysis.
..................................................................................................................... 195 Figure 95 Temperature distribution in the bridge seal - 28 days after seal placement
(summer). .................................................................................................... 196 Figure 96 Temperature distribution in the bridge seal and footing - 28 days after footing
placement (summer). ................................................................................... 197 Figure 97 Temperature distribution in the bridge seal, footing, and column - 28 days
after column placement (summer)............................................................... 198 Figure 98 Temperature distribution in the bridge seal, footing, column, and cap - 28
days after cap placement (summer). ............................................................ 199 Figure 99 Temperature development in the bridge seal (summer). ............................. 200 Figure 100 Temperature development in the footing (summer). ................................. 201 Figure 101 Temperature development in the column (summer). ................................ 201 Figure 102 Temperature development in the cap (summer). ....................................... 202 Figure 103 Temperature differential development in the bridge seal model (summer).
.................................................................................................................. 202 Figure 104 Temperature distribution in the bridge seal - 28 days after seal placement
(winter). .................................................................................................... 204 Figure 105 Temperature distribution in the bridge seal and footing - 28 days after
footing placement (winter). ...................................................................... 205 Figure 106 Temperature distribution in the bridge seal, footing, and column - 28 days
after column placement (winter). ............................................................. 206 Figure 107 Temperature distribution in the bridge seal, footing, column, and cap - 28
days after cap placement (winter). ........................................................... 207
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Figure 108 Temperature development in the bridge seal (winter)............................... 208 Figure 109 Temperature development in the footing (winter)..................................... 208 Figure 110 Temperature development in the column (winter). ................................... 209 Figure 111 Temperature development in the cap (winter)........................................... 209 Figure 112 Temperature differential development in the bridge seal model (winter). 210 Figure 113 Total strain development in the bridge seal - fib Model (summer). .......... 211 Figure 114 Stress development in the bridge seal - fib Model (summer).................... 211 Figure 115 Tensile strength development in the bridge seal - fib Model (summer).... 212 Figure 116 Crack development in the bridge seal - fib Model (summer).................... 212 Figure 117 Total strain development in the bridge seal - ACI Model (summer). ....... 213 Figure 118 Stress development in the bridge seal - ACI Model (summer). ................ 214 Figure 119 Tensile strength development in the bridge seal - ACI Model (summer). 214 Figure 120 Crack development in the bridge seal - ACI Model (summer). ................ 215 Figure 121 Total strain development in the bridge seal - fib Model (winter).............. 216 Figure 122 Stress development in the bridge seal - fib Model (winter). ..................... 216 Figure 123 Tensile strength development in the bridge seal - fib Model (winter). ..... 217 Figure 124 Crack width development in the bridge seal - fib Model (winter). ........... 217 Figure 125 Crack width in the bridge seal - fib Model (winter). ................................. 218 Figure 126 Total strain development in the bridge seal ACI Model (winter). ......... 219 Figure 127 Stress development in the bridge seal ACI Model (winter). .................. 219 Figure 128 Tensile strength development in the bridge seal ACI Model (winter). .. 220 Figure 129 Crack development in the bridge seal ACI Model (winter). .................. 220 Figure 130 Texas DOT Concrete Works predictions (TxDOT, 2019). ....................... 222 Figure 131 Volume and surface area corresponding to V/A ratio foundation.......... 227 Figure 132 Effect of V/A ratio on maximum temperature foundation. .................... 228 Figure 133 Effect of V/A on maximum temperature differential foundation........... 228 Figure 134 V/A, time elapsed, and maximum temperature foundation (summer). .. 229 Figure 135 V/A, time elapsed, and maximum temperature foundation (winter)...... 229 Figure 136 Temperature-time history for different V/A foundation (winter)........... 230 Figure 137 Effect of 45% replacement mixtures on maximum temperature foundation
(summer). ................................................................................................. 232
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Figure 138 Effect of 45% replacement mixtures on temperature differential foundation (summer). ................................................................................................. 232
Figure 139 Effect of 45% replacement mixtures on maximum temperature foundation (winter). .................................................................................................... 233
Figure 140 Effect of 45% replacement mixtures on temperature differential foundation (winter). .................................................................................................... 233
Figure 141 Total Tensile Strain vs. V/A ratio.............................................................. 234 Figure 142 Effect of increased slag content on maximum temperature in ternary
mixtures foundation (summer). ............................................................. 235 Figure 143 Effect of increased slag content on temperature differential in ternary
mixtures foundation (summer). ............................................................. 236 Figure 144 Effect of increased slag content on maximum temperature in ternary
mixtures foundation (winter).................................................................. 236 Figure 145 Effect of increased slag content on temperature differential in ternary
mixtures foundation (winter)................................................................. 237 Figure 146 Effect of ternary mixtures with 70% replacement level on maximum
temperature foundation (summer). ........................................................ 238 Figure 147 Effect of ternary mixtures with 70% replacement level on temperature
differential foundation (summer). ......................................................... 238 Figure 148 Effect of ternary mixtures with 70% replacement on maximum temperature
foundation (winter). ............................................................................... 239 Figure 149 Effect of ternary mixtures with 70% replacement on temperature differential
foundation (winter). ............................................................................... 239 Figure 150 Effect of w/c on maximum temperature foundation (summer). ............. 240 Figure 151 Effect of w/c on temperature differential foundation (summer). ........... 241 Figure 152 Effect of w/c on maximum temperature foundation (winter)................. 241 Figure 153 Effect of w/c on temperature differential foundation (winter). .............. 242 Figure 154 Effect of insulation on maximum temperature foundation (summer). ... 243 Figure 155 Effect of insulation on temperature differential foundation (summer). . 243 Figure 156 Effect of insulation on maximum temperature foundation (winter)....... 244 Figure 157 Effect of insulation on temperature differential foundation (winter). .... 244
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Figure 158 Volume and surface area corresponding to V/A ratio column. .............. 248 Figure 159 Effect of V/A ratio on maximum temperature column. ......................... 248 Figure 160 Effect of V/A ratio on temperature differential column. ........................ 249 Figure 161 Effect of V/A on time of maximum temperature column (summer)...... 249 Figure 162 Effect of V/A on time of maximum temperature column (winter). ....... 250 Figure 163 Temperature-time history for different V/A column (winter). ............... 250 Figure 164 Effect of 45% replacement mixtures on maximum temperature column
(summer). ................................................................................................. 252 Figure 165 Effect of 45% replacement mixtures on temperature differential column
(summer). ................................................................................................. 253 Figure 166 Effect of 45% replacement mixtures on maximum temperature column
(winter). .................................................................................................... 253 Figure 167 Effect of 45% replacement mixtures on temperature differential column
(winter). .................................................................................................... 254 Figure 168 Effect of increased slag content on maximum temperature column
(summer). ................................................................................................. 254 Figure 169 Effect of increased slag content on temperature differential column
(summer). ................................................................................................. 255 Figure 170 Effect of increased slag content on maximum temperature in ternary
mixtures column (winter). ..................................................................... 255 Figure 171 Effect of increased slag content on temperature differential in ternary
mixtures column (winter). ..................................................................... 256 Figure 172 Effect of ternary mixtures at 70% replacement level on maximum
temperature column (summer). ............................................................. 256 Figure 173 Effect of ternary mixtures at 70% replacement level on temperature
differential column (summer)................................................................ 257 Figure 174 Effect of ternary mixtures at 70% replacement level on maximum
temperature column (winter). ................................................................ 257 Figure 175 Effect of ternary mixtures at 70% replacement level on temperature
differential column (winter). ................................................................. 258 Figure 176 Effect of w/c on maximum temperature column (summer). .................. 259
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Figure 177 Effect of w/c on temperature differential column (summer).................. 259 Figure 178 Effect of w/c on maximum temperature column (winter). ..................... 260 Figure 179 Effect of w/c on temperature differential column (winter). ................... 260 Figure 180 Effect of insulation on maximum temperature with Control mixture
column (summer). .................................................................................... 261 Figure 181 Effect of insulation on temperature differential with Control mixture
column (summer). .................................................................................... 262 Figure 182 Effect of insulation on maximum temperature with Control mixture
column (winter). ....................................................................................... 262 Figure 183 Effect of insulation on temperature differential with Control mixture
column (winter). ....................................................................................... 263 Figure 184 Effect of insulation on maximum temperature with FA45 mixture column
(summer). ................................................................................................. 263 Figure 185 Effect of insulation on temperature differential with FA45 mixture column
(summer). ................................................................................................. 264 Figure 186 Effect of insulation on maximum temperature with FA45 mixture column
(winter). .................................................................................................... 264 Figure 187 Effect of insulation on temperature differential with FA45 mixture column
(winter). .................................................................................................... 265 Figure 188 Effect of insulation on maximum temperature of SL55+MK15 mixture
seal (summer). .......................................................................................... 268 Figure 189 Effect of insulation on temperature differential of SL55+MK15 mixture
seal (summer). .......................................................................................... 268 Figure 190 Effect of insulation on maximum temperature of SL55+MK15 mixture
seal (winter). ............................................................................................. 269 Figure 191 Effect of insulation on temperature differential of SL55+MK15 mixture
seal (winter). ............................................................................................. 269 Figure 192 Effect of insulation on maximum temperature of SL40+FA30 mixture seal
(summer). ................................................................................................. 270 Figure 193 Effect of insulation on temperature differential of SL40+FA30 mixture
seal (summer). .......................................................................................... 270
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Figure 194 Effect of insulation on maximum temperature of SL40+FA30 mixture seal (winter). .................................................................................................... 271
Figure 195 Effect of insulation on temperature differential of SL40+FA30 mixture seal (winter). ............................................................................................. 271
xxi

EXECUTIVE SUMMARY
This research study includes both experimental and analytical investigations of concrete mixtures containing supplementary cementitious materials to identify sustainable alternatives to Class F fly ash for use in Georgia's mass concrete structures. The primary goal of this study is to identify concrete mixtures that reduce the potential for thermal cracking caused by the heat of hydration of cementitious materials in order to optimize the long-term performance of mass concrete structures.
Two temperature components, maximum internal temperature and temperature differential, are critical to this work. A temperature differential occurs when the hydration heat produced in a mass concrete element is dissipated to the surrounding environment (e.g., water or air) and thus significantly lowers the surface temperature relative to the heat contained at the concrete core. When this happens, the internal temperature increases and causes an expansion of concrete at the core, whereas the surface temperature drop results in a significant contraction. A substantial temperature differential, one exceeding 35 F (19.4 C), inevitably results in thermal cracking which undermines durability in a newly placed mass concrete structure. An internal temperature increased beyond 160 F (71.1 C) yields another outcome detrimental to durability: thermal cracking from delayed ettringite formation.
Through this study, the research team has identified ternary replacement mixtures potentially suitable for mass concrete placements. Among the 45% cement replacement mixtures considered in this study, the ternary mixture composed of 30% slag and 15% metakaolin replacements achieves superior performance in terms of mechanical properties, durability, and thermal cracking potential from heat of hydration. In a case study involving
xxii

a bridge seal, however, the research team finds that circumventing substantial temperature differentials is extremely challenging, particularly for underwater concrete placements. Therefore, and especially in this context, the study team recommends that GDOT consider an increased cement replacement level (from 45% to 70%) and the use of insulating materials, if possible. Finally, the team has developed temperature prediction models based on a coupled thermal-structural analysis and corresponding charts to facilitate maximum temperature and temperature differential predictions.
Ultimately, the research team recommends that Georgia DOT (GDOT) consider changes to the Special Provisions to Section 500 (see Appendix A) and further study the performance of two ternary mixtures containing a 70% cement replacement with 1) 40% slag + 30% fly ash and 2) 55% slag + 15% metakaolin in order to reduce the potential for thermal cracking and thus optimize the long-term performance of mass concrete structures in Georgia. Future work should include identifying other sustainable alternatives to fly ash and performing coupled thermal-structural analyses to parametrically design mass concrete structures free of thermal cracks.
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ACKNOWLEDGEMENTS The University of Georgia greatly appreciates the financial support provided by GDOT for this work. The authors would like to thank the personnel at GDOT who assisted with this study. A special thanks to Dr. Peter Wu (Office of Materials and Testing) who advised the research team in successfully performing the study and Mr. David Jared, P.E. (Office of Performance-based Management and Research) for his research support and provision of pertinent information. Finally, the study team would like to acknowledge and thank Sunil Thapa for helping us finalize this report. This report includes major findings of the research study completed by Hiwa Hamid in partial fulfillment of his PhD degree requirements. Matthew Sullivan (MS in Engineering, University of Georgia) is acknowledged for his significant contribution to the experimental work presented in Section 2.2. Finally, Lewis Goode is acknowledged for his contribution to the experimental work presented in Section 3.3.2.
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1. INTRODUCTION
This section presents the background information, objectives, significance, and methodology employed in this study.
Background The first subsection introduces the basic knowledge and design principles required to understand the thermal behavior of concrete structures. In addition, the benefits of supplementary cementitious materials (SCMs) (e.g., metakaolin (MK) and granulated blast furnace slag (hereafter referred to as `slag' in the text and `SL' in mixture notations)), particularly for improving durability and reducing the heat of cement hydration, are presented herein.
Concrete Behavior and Elevated Temperature Simple facts about thermal loading and concrete behavior
Understanding the fundamental behavior of concrete structures subject to elevated temperatures is critical to a discussion of the thermal design procedures. Thermal loads are induced when natural changes in length or volume are fully or partially restrained due to temperature variations. In effect, thermal loading is strain loading due to temperature change in partially or fully restrained structural members. Increased temperature is represented by increased strain, t, regardless of restraint conditions (free or fixed), as shown in Figure 1, where denotes the coefficient of thermal expansion (e.g., 5.5x10-6/F or 10x10-6/C for concrete). In reinforced concrete structures, reinforcing steel generally expands as much as concrete when the temperature increases.
1

Figure 1 1D thermal expansion. In designing concrete structures, concrete compressive strain and reinforcing steel tensile strain need to be evaluated for load combinations (i.e., combined structural and thermal loading). When a structure is restrained from a rotation but is subjected to a temperature gradient, the hotter side generally results in compression. In this situation, concrete crushing becomes the main concern, as in Figure 2, which shows a reinforced section of a foundation structure. On the other hand, the colder side (i.e., the other face) is in tension, ultimately causing the reinforcing steel to yield. As per the American Concrete Institute (ACI) 318 requirements for the ultimate design, reinforcing steel can yield for temperature loading; however, the degree of concrete cracking may affect the serviceability of concrete members and thus may ultimately compromise the structure's primary function. Therefore, strains in reinforcing steel are often limited to 1.2y (ACI 349, 2013) for controlling crack widths in leak-tight structures. Tolerable crack widths range between 0.004 inch (0.10 mm) and 0.016 inch (0.40 mm) according to the International Federation for Structural Concrete (fib) (fib, 2013) and ACI (ACI 224R-07, 2007) design guidelines, depending on a structure's environmental exposure.
2

Figure 2 Temperature profile through a typical reinforced concrete section.
Temperature increase or decrease Temperature changes in mass concrete structures are mainly attributed to temperature variations from the heat of cement hydration as well as seasonal temperature changes on surfaces exposed to air (or water). A temperature change is calculated with respect to an initial (or reference) temperature, Tinitial. As the temperature increases to Televated (or Tmaximum) on one side of a reinforced concrete section, the temperature distribution throughout the section is nonlinear but ultimately converges to a linear steady-state condition, as shown in Figure 2. This linear temperature profile is determined such that area `b' is equivalent to areas `a' and `c' combined. Seasonal changes may reverse stress states, and thus both summer and winter conditions need to be evaluated unless inspection deems one condition more critical.
Uniform temperature increase and gradient temperature Often, the linear temperature distribution is divided into a uniform temperature increase, Tu, and a temperature gradient, Tg, as shown in Figure 3. These values are described as increased and differential temperatures for analysis, respectively, and they do not exist as physical values in structures. A thermal model determines the time-dependent and
3

nonlinear temperature distributions for a structure. A structural model uses the temperature distribution (i.e., loading) at a selected time to generate elastic thermal strains. There is no need to linearize the temperature distribution as long as the same geometry is used in the structural analysis to read temperatures node-by-node from the corresponding thermal model; however, a temperature analysis is often simplified to provide a linear temperature profile for a structural analysis. This process sometimes results in multiple temperature profiles at different locations of a reinforced concrete structure, thereby creating discontinuous temperature assignments at junctions. For this reason, a nonlinear and coupled thermal-structural analysis is highly recommended. In general, a uniform temperature increase yields uniform strain, u, and a gradient temperature yields both compressive and tensile strains, g, in a section (see Figure 3).
Figure 3 Linear temperature profile.
4

Behavior of concrete members Most concrete members are partially restrained from thermal expansion. Figure 4(a) presents the free expansion of a concrete beam as well as a fully-restrained beam member. When a concrete member is free to expand, there is no thermal stress. When the member is fully restrained, thermal stresses are generated. These, in turn, are used to determine internal thermal forces. Internal stress, , and force are simply determined by . . and . . , respectively, for a temperature change, . For other partially restrained structures, the axial force in the concrete member ranges from 0 to . . . The same idea applies to calculations for member rotations, , and moment, M, as shown in Figure 4 (b). Young's modulus, cross-section area, gross section moment of inertia, and thickness of a reinforced concrete section are represented by E, A, I, and t, respectively, in Figure 4.
(a) expansion restrained
5

(b) rotation restrained Figure 4 Reinforced concrete members restrained from thermal expansion and
rotation.
Figure 5 Degree of restraints and thermal stresses. Thermal stress and restraints As shown above, the degree of restraints and the gradient temperature affect the amount of thermal stresses generated in a concrete member. Fully restrained concrete members yield
6

the worst design case, producing the largest thermal strains/stresses. In designing concrete structures for elevated temperatures, members should have as few restraints as possible. Figure 5 portrays an increase in thermal stress as a linear function of the degree of restraints in a concrete member to illustrate this important concept.
Supplementary Cementitious Materials Natural pozzolans, such as metakaolin (MK), calcined shale, and calcined clay, are materials that contribute to the properties of hardened concrete through hydraulic or pozzolanic activity or both when used in conjunction with Portland or blended cement. Natural pozzolans are classified by ASTM C 618 (AASHTO M 295) as Class N pozzolans.
A pozzolan is a siliceous or alumino-siliceous material that chemically reacts in finely divided form and in the presence of moisture with the calcium hydroxide released by the hydration of Portland cement to form calcium silicate hydrate (CSH) and other cementitious compounds. Pozzolans and slags are generally categorized as supplementary cementitious materials (SCMs) or mineral admixtures (PCA, 2011). The most common natural pozzolans used today are processed materials, heat-treated in a kiln before they are ground to a fine powder; they include calcined clay, calcined shale, and MK. MK, a special calcined clay, is produced by the calcination of high purity kaolin clay at low temperatures. The product is ground to an average particle size of 1 to 2 mm (PCA, 2011).
Concrete mixtures including supplementary cementitious materials are generally defined as binary or ternary replacement mixtures. Binary replacement mixtures are defined as Portland cement and one supplementary cementitious material. Ternary mixtures are defined as Portland cement and two other supplementary cementitious materials, or blended cement and one other supplementary cementitious material.
7

When MK is used as a partial cement replacement, improved performance has been observed, as characterized by increased strength and reduced permeability, for instance (Marikunte & Phelps, 2012). Marikunte and Phelps (2012) statistically demonstrated that replacing cement with MK contributes more to concrete achieving high performance than reducing water content. San Nicolas et al. (2014) concluded that MK substitution (25% by weight) improves the durability of concrete. Ferreira et al. (2015) reported improved strength, durability properties, and chloride penetration resistance for concrete with MK. When MK is used as a cement replacement with Class F fly ash (hereafter referred to as `fly ash' in the text and `FA' in mixture notations), Khatib et al. (2009) found reduced concrete shrinkage. In addition, Lagier and Kurtis (2007) found that MK use accelerated the hydration process as a result of its higher surface area, though Brykov et al. (2015) reported that this acceleration depends on MK dosage. Due to the enhanced durability of highly reactive MK, the material is widely used for concrete overlay designs by Illinois, Iowa, and several other state departments of transportation (DOTs). Altogether, research has documented the following advantages of using MK as a partial cement replacement:
Increased compressive and flexural strengths Increased resistance to chemical attack and durability Enhanced workability Improved color by lightening the color of concrete Reduced effects of alkali-silica reactivity (ASR) Reduced permeability and shrinkage Reduced potential for efflorescence
8

When the authors commenced this study in 2015, a brief review of how DOTs specify and/or use MK was conducted from publicly available DOT websites. Most DOTs refer to the chemical requirements of either the American Society for Testing and Materials (ASTM) C168 or American Association of State and Highway Transportation Officials (AASHTO) M321 for MK for use in hydraulic cement. The Illinois DOT shared a special provision for ASR mitigation requirements where the average alkali content (Na2O + 0.658 K2O) of high reactivity MK must be less than 1.0%. In addition, the content of silicon dioxide (SiO2), aluminum oxide (Al2O3), and iron oxide (Fe2O3) must exceed 80%. Meanwhile, the Texas DOT shared an 85% requirement for the same chemical composition (DMS-4635, 2014). For sulfate resistance, the Colorado DOT required high reactivity pozzolan mixtures to have less than 0.10% expansion at 18 months when tested according to ASTM C 1012; Class 2 concrete required less than 0.05% expansion within 6 months. The Minnesota DOT limited MK to 10% of Portland cement by weight, whereas the use of fly ash and slag was limited to 20% of Portland cement by weight. The Missouri DOT approved a maximum of 15% replacement of Portland cement on a pound for pound basis in all concrete. The California DOT recommended MK to be used in dosages ranging from 5%10% by mass of the cementitious material. The Montana DOT allowed up to 20% replacement by weight of the total cementitious material. Ramezanianpour & Jovein (2012) recommended optimum replacement of MK between 12.5% and 10% at water-to-cement ratios of 0.4 and 0.35, respectively. In Nebraska, the maximum pozzolanic content should not exceed 1525% of the total cementitious material. Wisconsin required MK suppliers to be included on the DOT's approved product list and have a quality management program in place with daily testing performed to determine uniformity. The Phase-I investigation of
9

this project (see Chorzepa et al., 2017) and Section 3 of this report provide a more detailed and recent literature review.
The Georgia Department of Transportation's (GDOT's) current specification for mass concrete (Special Provision to Section 500 (Concrete Structures) - Standard Specifications), hereafter referred to as "Special Provision" includes a maximum allowable internal temperature of 158 F (70 C) and a temperature differential of 35 F (19.4 C) between interior and exterior portions of the designated mass concrete element. The Special Provision also specifies that slag, fly ash, and a combination of different pozzolans may comprise no more than 75%, 40%, and 75% by mass of total cementitious and pozzolanic materials, respectively.
With a shortage of fly ash and imported slag in the state, SCMs such as MK are considered to control the heat of hydration (HoH) despite some disagreement in the literature on the effect of microsilica (or MK) on HoH. While in a previous study by (Meland, 1983), the replacement of cement by 10% and 20% microsilica slightly reduced early HoH, other studies (Alshamsi, 1997) showed an increase in HoH. This research highlights how the physical characteristics and chemical composition of MK influence its ability to affect HoH. Alshamsi (1997) limited cement replacement to 10%, and the chemical composition of MK at that time differed from what is available in today's market. Accordingly, it is necessary to evaluate currently available MK products to reduce HoH in mass concrete elements. In a recent study, increased MK replacement from 10% to 14% minimized the total heat evolved, although 10% was found optimal when also considering mechanical properties (Jiang et al., 2015).
10

An extensive survey of state DOTs' specifications and other available resources is necessary to fully understand current practices and challenges in relation to the usage of MK and other SCMs as partial replacements for cement. It is also essential to determine whether and how MK should be specified.
Problem Statement Fly ash is an important SCM used in mitigating deleterious cracking from large thermal gradients in mass concrete. However, the coal market may not be able to sustain the current volume of fly ash used in U.S. concrete structures. The Mid-Atlantic region has experienced a fly ash shortage, which in turn may impact cement concrete producers and thus construction material costs for GDOT projects. Thus, evaluating alternative SCMs is critical to maintain the market habits of the ready-mix industry. MK is a locally available option for Georgia, and several state DOTs have already adopted and specified commercial MKs for use in concrete. Even though Georgia is a world-leading kaolin producer, the use of MK has yet to be addressed in GDOT's standard specifications.
The United States Geological Survey (USGS) estimates that nearly 8.5 million metric tons of kaolin are mined from Georgia each year (USGS, 2013). Kaolin has many existing applications: ceramics, toothpaste, paint, cosmetics, and others. According to the Georgia Mining Association, the kaolin industry in Georgia employs over 4,400 Georgians, which amounts to over $232 million in pay and benefits (Georgia Mining Association, 2016). Unlike secondary materials such as fly ash, silica fume, and slag, MK is not the byproduct of another process.
Mass concrete placements demand considerable control of temperature rise due to the HoH of cementitious materials. Typical temperature rise in concrete mixtures ranges
11

between 80 F (44.4 C) and 100 F (55.6 C). The ACI recommends a placement temperature of 58 F (14.4 C) for 100 F (55.6 C) temperature rise concrete; however, this temperature requirement proves to be particularly challenging in Georgia. Generally, the temperature rise at concrete placements can be reduced to 70 F (38.9 C) with a large percentage of Portland cement replaced with fly ash or slag. However, there has been a shortage of fly ash and slag, so these materials have been replaced with alternative binder systems to allow reductions in temperature for mass concrete construction (e.g., large columns and foundations for bridges and other transportation structures).
Cement hydration produces an internal temperature rise; meanwhile, the outer concrete surface cools faster than the section core. Through thermal expansion/contraction, the temperature differential induces thermal stresses at the surface. Once the maximum interior temperature exceeds the accepted threshold value, delayed ettringite formation (DEF) can occur in mass concrete elements. Accordingly, DEF can be prevented by limiting the internal temperature of concrete from the outset. The maximum temperature suggested by prior research to prevent DEF in concrete elements is 160 F (71.1 C). This reduced temperature threshold can be achieved by specifying allowable initial temperatures, limiting cement content, or using low heat SCMs.
Currently, GDOT specifications do not explicitly specify the cement replacement limit on Class N pozzolan in concrete. With the availability of kaolin in middle Georgia, GDOT can take advantage of this material to decrease the demand for cement and fly ash as well as improve the overall properties of concrete mixtures. Furthermore, GDOT can control the maximum internal temperature and the temperature differential in mass concrete elements by incorporating SCMs such as MK and/or slag.
12

Research Objectives This study aims to find natural, lightly processed, and economical alternatives to fly ash that perform similarly with regard to pozzolanic reactivity and provide comparable compressive strength, workability, drying shrinkage, thermal expansion properties, and resistance to ASR, sulfate attack, and chloride-ion penetration. Accordingly, this study investigates ternary replacement mixtures involving a combination of slag and MK products. As a pozzolan, MK would improve concrete performance through decreased permeability, improved strength and durability, and reduced shrinkage.
The study identifies the appropriate limits of MK to be used in mixtures and describes subsequent concrete performance. Appropriate usage of MK in both binary and ternary concrete mixtures will be discussed, along with preliminary specifications for its usage in GDOT mass concrete structures. Current GDOT specifications for mass concrete (Special Provision to Section 500) will be reviewed, and changes will be recommended based on the findings of this study.
Research Significance and Scope The primary benefit of this study is to identify reasons for adopting Class N pozzolan MK as a viable option for inclusion in concrete specifications. This project will provide appropriate supporting information for its acceptance or rejection. Furthermore, the benefits of using commercially available slag products are investigated. If MK and/or slag are deemed acceptable, GDOT would have access to viable SCMs local to Georgia.
This study focuses on reducing the heat of hydration by means of cement replacement materials without relying on active cooling systems.
13

Research Methodology To accomplish the aforementioned objectives, experimental and analytical methods are deployed in five specific tasks. These tasks are outlined below.
Task 1. Perform Extensive Literature Review A thorough review of specifications developed by other state DOTs is conducted to provide insight into current issues, practices, and challenges pertaining to MK (and/or slag) usage or in mass concrete mixtures.
Task 2. Design, Batch, and Test Concrete Mixtures with Three Metakaolin Products This task includes designing, batching, and testing concrete mixtures with cement replacements of MK while evaluating the replacement threshold limit to satisfy the current performance requirements outlined in GDOT Section 430 Concrete Pavement (Classes 1 and 2) and Section 500 Concrete Structures (Classes AAA, AA1, AA, A, B, and CS). Three locally sourced MK products, along with two slag products, are studied. Task 2 results are presented in Section 2.
Task 3. Design, Construct, and Quantify Temperature Rise in Mass Concrete Results from this task are presented in Section 3. The following subsections provide a summary of Task 3.
Task 3.1 - Design test procedures for mass concrete mixtures A test matrix consisting of different combinations of MK and other SCMs (e.g., slag) is developed to quantify temperature rise from the heat of cement hydration. Figure 6 illustrates the test layout and specimen size used for a similar study conducted by the CTL
14

Group (Gajda et al., 2014). Gajda et al. (2014) found the heat generated from cement hydration was rapidly dissipated even though 6-inch (15.24 mm)-thick insulation panels were employed. Accordingly, a more efficient insulation material is selected in this study, and the specimen size is reduced from a 3 foot x 3 foot x 3 foot (0.91 m x 0.91 m x 0.91 m) cube specimen to a 2 foot x 2 foot x 2 foot (0.61 m x 0.61 m x 0.61 m) cube specimen.
Figure 6 Test layout for concrete cube placement (Gadja et al., 2014). Task 3.2 Construct cube molds and specimens Cube molds are constructed with the 6-inch-thick (152.40 mm) Kingspan Kooltherm K20 Concrete Sandwich Board insulation panels shown in Figure 7. On all six sides of the cube specimen, these insulation panels are sandwiched between a 1-inch-thick (25.4 mm) plywood sheet and a stainless steel liner. A detailed procedure is presented in Section 3.
Figure 7 Kingspan Kooltherm K20 Insulation (Kingspan USA, 2019).
15

Task 3.3 Internal temperature monitoring in test specimens Concrete mixtures are placed in the mold constructed from Task 3.2. Temperature rise over time is monitored for each specimen using thermocouples for 14 days.
Task 4. Evaluation of Maximum Temperature Limits Results from this task are presented in Section 4. The following subsections provide a summary of Task 4.
Task 4.1 Thermal and structural modeling A Finite Element Analysis (FEA) of a mass concrete structure is completed using the DIsplacement ANAlyser FEA software (DIANA FEA, Version 10.2). A transient thermal analysis and a nonlinear structural analysis (i.e., a coupled thermal-stress analysis) are performed by simulating the placement and boundary conditions of the mass concrete specimens from Task 3. The FEA model is validated using the experimental results from Task 3, as well as an experimental study conducted by others (Jung et al.'s (2017)).
Task 4.2 Design and construct test specimens Task 3 determines the maximum internal temperature of insulated cube specimens. In addition to the maximum allowable internal temperature, the maximum allowable temperature differential, T, is needed to assess the extent of temperature-induced cracking in mass concrete. To identify a practical range of allowable temperature differentials and quantify tensile strains in mass concrete, concrete cylinders exposed to elevated temperatures are evaluated.
The following two temperature threshold scenarios are initially considered for implementation in GDOT's mass concrete specification (see Table 1):
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1) Maximum allowable internal temperature of 158 F (70 C) & maximum temperature differential of 50 F (27.8 C), yielding the total temperature of 208 F (97.8 C).
2) Maximum allowable internal temperature of 170 F (76.7 C) & maximum temperature differential of 35 F (19.4 C) (if deemed feasible), reaching the total temperature of 205 F (96.1 C).

Table 1 Maximum allowable internal and differential temperature limits.

Temperature Limits

Maximum Allowable Temperature, Maximum Temperature Differential,

F (C)

F (C)

158 (70)

50 (27.8)

170 (76.7)

35 (19.4)

Task 4.3 Evaluation of temperature limits This task includes a coupled thermal-structural analysis of mass concrete structures with varying placement configurations. The following placement configurations are evaluated: 1) 5-foot (1.5 m)-thick foundation, 2) 8-foot (2.4 m)-diameter column, and 3) 43.25 foot x 19.5 foot x 22.25 foot (13.2 m x 5.9 m x 6.9 m) seal (with rebar/steel cage
in the middle).
The following two variables are considered to evaluate maximum temperatures and study the extent of cracking in mass concrete structures, and the results are presented in Section 5: 1) Varying surface temperature conditions (e.g., Georgia's winter/summer temperatures)
and environmental conditions
17

2) Varying volume-to-surface area (V/A) ratios of mass concrete elements (e.g., concrete seals, foundation structures, and large columns)
Task 5. Data Analysis and Synthesis of Findings The results, based on observations, previous studies, and data collected from laboratory testing, are analyzed to recommend whether and how to specify MK for GDOT. Further, allowable temperatures for maximum internal temperature and temperature differential are reviewed for implementation in the mass concrete provision.
Implementation Appendices A and B present recommendations to the existing Special Provision to Section 500. Based on findings from this study, the following outcomes are provided: 1) Identification of appropriate limits of MK for implementation in GDOT specifications 2) Identification of the maximum allowable internal temperature and temperature
differential for concrete mixtures incorporating SCMs such as fly ash, slag, and MK for implementation in GDOT specifications 3) Recommended changes to the Special Provision to Section 500 Concrete Structures (GDOT, 2013)
Organization of the Report This report is divided into seven sections that describe test procedures for binary and ternary cement replacement mixtures and present results from these tests, which include 1) An experimental investigation of HoH in various mixtures, 2) An analytical investigation of mass concrete specimens and a bridge foundation seal,
and
18

3) A sensitivity analysis of maximum temperatures and temperature differentials by varying V/A ratios and mixture designs.
Section 1 presents a general background on the thermal design of concrete structures and the use of SCMs, specifically MK and slag. Additionally, research objectives and significance are described.
Section 2 describes an experimental investigation of concrete mixtures containing various SCMs: MK, slag, and fly ash products. This section offers insight into the effect of different SCMs and replacement levels on HoH, mechanical properties, durability, and dimensional stability. This is a continuation of work performed in the Phase-I investigation (see Chorzepa et al., 2017).
Section 3 presents an experimental investigation designed to measure HoH and temperature in mass concrete specimens. These specimens contain varying amounts of SCMs with various cement replacement levels. This section also provides a literature review on mass concrete specifications and other standard specifications across the state DOTs.
Section 4 outlines an analytical investigation of mass concrete structures using the Finite Element Analysis (FEA) method. Findings from existing research validate this simulation procedure. Finally, a case study involving a bridge seal structure is presented.
Section 5 presents a sensitivity analysis that considers the effects of different parameters (e.g., V/A ratios, mixtures designs, and placement conditions) on the maximum temperature and temperature differential of mass concrete structures.
Section 6 synthesizes the findings and presents the conclusions of this project. Section 7 provides recommendations.
19

Finally, Appendices A and B outline recommended changes to GDOT's current mass concrete special provision, Appendix C provides additional supplementary recommendations from the state DOTs, Appendix D presents the thermal analysis of a bridge seal with a rectangular column, and Appendix E gives additional validation of strain from gradient temperature.
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2. COMPARISON OF BINARY AND TERNARY MIXTURES A portion of this section was presented as part of the Phase-I study (see Chorzepa et al., 2017). However, this Phase-II study includes additional binary and ternary replacement mixtures. Results from both Phase-I and Phase-II studies are presented herein in order to synthesize results. Section 2.1 presents mixture designs based on the HoH of cementitious materials, and it is a portion of a study performed by Hamid et al. (2018). In Section 2.2, mechanical and durability properties of 19 selected mixtures are presented.
Preliminary Investigation into Heat of Cementitious Material Hydration As a preliminary investigation, the HoH performance of selected binary and ternary replacement mixtures involving different SCMs is studied. Detailed HoH tests on all the mixtures are presented in Section 3.2.
Experimental Design Eight mortar mixtures are prepared for the HoH test using the isothermal calorimeter shown in Figure 8. The mixtures consist of a Control mixture, a MK binary replacement mixture (15% MK), two slag binary replacement mixtures (30% and 45% slag), a fly ash binary replacement mixture (45% FA), and three ternary replacement mixtures including slag and MK for a total of 45% cement replacement. Replacement levels and mixture designations are shown in Table 2.
21

Table 2 Mixtures used for HoH testing.

Percent Cement Replacement (%)
15 30
45

Mixtures
MK-15 SL-30 SL-45 FA-45 SL-40+MK-5 SL-35+MK-10 SL-30+MK-15

The external mixing method per ASTM C1702 (ASTM C1702, 2017) is used to prepare isothermal calorimetry specimens (120 mL or 4 oz.) for HoH testing. In this study, mortar specimens are prepared from large (4 cubic feet or 0.11 cubic meter) batch concrete mixtures by screening out the coarse/fine aggregate using a No. 5 sieve. This procedure is consistent with the ASTM procedure. In this method, the temperature of the calorimeter is maintained constant at 73.4 F (23 C), and data (e.g., power and energy output of the samples) is collected for seven days.

Figure 8 Isothermal calorimeter used for HoH testing. 22

Results HoH results are presented as well as the percentage reduction or increase in HoH in all binary and ternary mixtures, relative to the Control mixture, at 1, 3, and 7 day(s) of hydration. Table 3 presents a summary of the findings.

Table 3 Percent reduction in HoH in binary and ternary mixtures.

Percent cement replacement (%)
15 30
45

Mixtures
MK-15 SL-30 SL-45 FA-45 SL40+MK5 SL35+MK10 SL30+MK15

% Reduction in HoH relative to the Control specimen

1 day (%)

3 day (%)

7 day (%)

-9

-3

5

-22

-13

-2

-28

-18

-8

-42

-36

-32

-30

-16

-7

-26

-16

-8

-36

-20

-13

Heat of hydration in binary mixtures including metakaolin Figure 9 presents the thermal power per gram of cementitious materials for the MK binary replacement mixture. The rate of heat generation in the MK mixture is similar to the Control mixture while the amplitude of thermal power is reduced by about 4% in the MK mixture. Figure 10 presents HoH results for the MK mixture. Compared to the Control mixture, HoH at 1 and 3 days are reduced by 9% and 3%, respectively, in the MK15 mixture. The HoH for the MK-15 mixture is comparable to that of the Control mixture by 84 hours and exceeds it by 5% at 7 days. This corresponds to the results found in the literature (Maia et al., 2011; Snelson et al., 2008).

23

Figure 9 Rate of heat flow in the Control and MK mixtures.
Figure 10 HoH in the Control and MK mixtures. The rate of heat flow from Figure 9 shows a negative value in the early age hydration of the Control mixture. This negative-valued endotherm results from early (<2 hrs.) temperature acclimation of the specimen and does not affect the main hydration peak.
24

The hydration process of the mixtures is divided into stages as determined by letters A through D. Point A represents initial thermal power, which is caused by the rapid dissolution and initial hydration of the aluminate phase. Point B represents a dormant period associated with very low thermal power, indicating slow and well-controlled hydration (ASTM C1679-17, 2017). Point C represents the main hydration peak in the acceleration period, mainly attributed to the silicate reaction and initiation of the strengthgenerating alite or silicate hydration. Point D represents the accelerated calcium aluminate activity attributed to the second C3A dissolution; this activity results from the high exothermic dissolution of aluminate and continued formation of ettringite (Berodier, 2015; Gallucci et al., 2010; ASTM C1679-17, 2017). In the Control mixture, the magnitude of point D is comparable to point C. However, in the MK binary mixture, point D is located much higher than point C on the y-axis. A similar trend is observed in the ternary and other binary mixtures, which are presented in the next section (Section 2.1.2.2). This is due to the pozzolanic reaction between calcium hydroxide (CH) and SCMs (Berodier, 2015; Wu et al., 1983).
Heat of hydration of ternary and other binary replacement mixtures Figure 11 presents the thermal power for the ternary and alternate SCM binary mixtures. Figure 12, meanwhile, portrays the HoH for the ternary and alternate SCM binary mixtures over seven days. The 45% fly ash replacement mixture has a very slow rate of HoH and significantly reduces the heat energy by 42%, 36%, and 32% at 1, 3, and 7 days of hydration, respectively. The HoH of the SL-30 mixture is lower than the Control mixture at all ages, but it is higher than the FA-45 mixture. The SL-30 mixture reduces the 1-, 3-, and 7-day HoH by 22%, 13%, and 2%, respectively. This result aligns with previous
25

findings (Arora, Sant, & Neithalath, 2016; Bohc et al., 2014; Pane & Hansen, 2005), in which the 3- and 7-day HoH were reduced by approximately 15% and 3%, respectively, when 2055% of cement was replaced by slag. The rate of heat generation is reduced in the binary slag mixtures, and this reduction is even more evident in the ternary SL-30+MK15 mixture. A significant reduction in the rate of heat generation and total cumulative HoH is observed in this ternary mixture for up to seven days. The 1-, 3-, and 7-day HoH are reduced by approximately 35%, 20%, and 13%, respectively, in the ternary mixture relative to the Control mixture.
Figure 11 Thermal power of the ternary and alternate binary mixtures.
26

Figure 12 HoH of the ternary and alternate binary mixtures. Heat of hydration of ternary mixtures with various percentages of slag and metakaolin Figure 13 and Figure 14 show the effect of ternary replacement mixtures containing various amounts of slag and MK on thermal power and HoH. Among the mixtures, SL-30+MK-15 offers the most reduction in heat energy, and this reduction is lower than that of the SL-45 mixture. Table 3 presents the percent reduction in HoH in all mixtures over the Control mixture.
27

Figure 13 Thermal power of ternary mixtures with various percentages of slag and MK.
Figure 14 HoH of ternary mixtures with various percentages of slag and MK. 28

Table 3 Repeated Percent reduction in HoH in binary and ternary mixtures.

Percent cement replacement (%)

Mixtures

Percent reduction in HoH relative to the Control specimen

1 day (%)

3 day (%)

7 day (%)

15

MK-15

-9

-3

5

30

SL-30

-22

-13

-2

SL-45

-28

-18

-8

FA-45

-42

-36

-32

45

SL-40+MK-5

-30

-16

-7

SL-35+MK-10

-26

-16

-8

SL-30+MK-15

-36

-20

-13

This study employs 45% cement replacement mixtures. The optimal replacement composition of a ternary mixture is determined by studying HoH in the following mixtures: SL-45, SL-30+MK-15, SL-35+MK-10, and SL-40+MK-5. It was anticipated that SL-45 would result in the lowest HoH since other mixtures contain MK, which affords a greater capacity for pozzolanic activity than slag (Mindess et al., 2003). Contrary to this expectation, the SL-30+MK-15 mixture leads to the lowest HoH, as shown in Figure 14. Table 3 shows that the ternary replacement mixture of SL-30+MK-15 comes in second to the FA-45 mixture in reducing HoH among all the mixtures. These results illustrate that the optimum ratio of pozzolans used in ternary replacement mixtures is 2SL:1MK when a 45% ternary replacement is considered.

Analysis of Results Effect of metakaolin binary mixture on heat of hydration
The partial replacement of cement with 15% MK in the binary mixture results in no significant change in HoH. The heat of cement hydration is initially reduced by removing

29

15% of the Portland cement by weight; however, the pozzolanic reaction takes place after about two days and adds to the total heat generated.
Effect of binary mixtures containing fly ash and slag on heat of hydration The slow rate of heat generation in the fly ash mixture is attributed to the relatively low specific surface area and the low solubility of the alumino-silicate glass in the alkaline environment of the Portland cement hydration (Snelson et al., 2008). The slag mixture has a higher calcium oxide (CaO) content compared to the fly ash mixture, which may in turn result in a corresponding increase in heat generation.
Effect of ternary mixtures on heat of hydration In this study, SL-30+MK-15 reduces the 1-, 3-, and 7-day HoH by 36%, 20%, and 13%, respectively, compared to those of the Control mixture. These results align with a previous study by Bohc et al. (2014), where the 3-day HoH was reduced by about 60% in a SL30+MK-5 mixture. In the same study by Bohc et al., however, a SL-40+MK-15 mixture unexpectedly increased the 3-day HoH by 27% from that of the SL-30+MK-5 mixture despite the increase in cement replacement from 35% to 55%. For Bohc et al. (2014), the percentage of SiO2 and Al2O3 in MK was 57.3% and 38.6%, respectively, whereas in this study, MK contains 50.8% SiO2 and 45.9% Al2O3. Thus, additional alumina content may confer different heat releases.
The ternary mixtures include aluminate, possibly a sufficient amount for the formation of calcium aluminate sulfate (AFt or ettringite). When pozzolans contain aluminate, AFt phases can form during the pozzolanic reaction. Moreover, the ternary mixtures also have a high level of silicate which results in the formation of additional CS-H. Aluminate hydration reacts with CSH and releases calcium carbonate, which is known
30

to convert AFt phases to monocarbonate. Bohc et al. (2014) indicate that little to no AFt is found in ternary mixtures including slag and MK, whereas it was found in binary mixtures with MK. The presence of water-rich AFt increases the total volume of hydration products, and thus the total amount of heat is relatively lower in ternary mixtures due to the absence of AFt. At the same time, combined alumina and silica content appears to affect the total amount of heat.
Based on the findings presented in this section, the presence of two pozzolanic materials with high contents of alumina and silica in ternary replacement mixtures results in reduced heat release, as well as adequate strength development as discussed in Section 2.2. Table 4 provides the ratios of calcium to alumina (Ca/Al), calcium to silica (Ca/Si), and calcium to alumina and silica (Ca/(Al+Si)) for the ternary and binary mixtures consisting of fly ash or slag at 45% replacement level. In the context of the findings discussed above, this table illustrates that the amount of heat is proportional to the Ca/(Al+Si) ratio.

Table 4 Oxide ratios for select 45% replacements.

Mixtures Control SL-45 FA-45 SL-40+MK-5 SL-35+MK-10 SL-30+MK-15

Ca/AL 13.5 6.2 3.1 5.0 4.1 3.49

Ca/Si 3.2 2.1 1.1 1.9 1.8 1.7

Ca/(AL+Si) 2.6 1.6 0.8 1.4 1.3 1.1

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Estimating the Heat Generated from Pozzolanic Materials In order to isolate heat released from pozzolanic reactions, heat released solely from cement hydration in each binary and ternary mixture is estimated by linearly extrapolating the HoH obtained from the Control mixture as shown in Figure 15. Heat generated from the pozzolanic reaction in each mixture is then estimated by deducting heat released from cement hydration, as shown in Figure 15, from the total HoH of each mixture shown in Figure 10, Figure 12, and Figure 14. The same approach for separating the HoH of slag from that of Portland cement in blended mixtures is used by Gruyaert et al. (2010) and Meinhard & Lackner (2008). Figure 16 shows the estimated heat released solely from the presence of pozzolanic materials in each mixture. The shape and slope of the curves indicate the pozzolanic reaction's rate. Here, though, a comparison should only be made between mixtures of the same cement replacement levels. For instance, a fair comparison is made between the 45% replacement mixtures, SL-45 and SL-30+MK-15.
32

Figure 15 Linear extrapolation of HoH for the Control mixture.
Figure 16 HoH generated from the pozzolanic reaction. 33

Estimated heat of hydration in binary mixtures including metakaolin Figure 16 shows that the pozzolanic reaction of the binary mixture MK-15 starts after two days and mainly occurs between two and five days. The heat release rate is initially high in the MK mixture. This may be attributed to the chemical composition of MK, which is high alumina content accelerates the pozzolanic reaction (Curcio et al., 1998). In the MK15 mixture, the heat released reaches a plateau at seven days, indicating that the initial CH produced from cement hydration has been mostly depleted within a week (Mindess et al., 2003). This heat generation rate in the MK mixture is consistent with its compressive strength development, as shown in Section 2.2.2.1. In the MK-15 mixture, the rate of strength development is highest between one and seven days.
Estimated heat of hydration in ternary and alternate binary mixtures Among the 45%-replacement-level mixtures, SL-35+MK-10 and SL-40+MK-5 have the highest rate of pozzolanic reaction followed by the SL-45 mixture. The ternary replacement SL-30+MK-15 mixture shows a lower pozzolanic reaction than the SL-45 mixture. On the other hand, the FA-45 mixture shows a very slow heat release rate (or pozzolanic reaction over time). This is consistent with the compressive strength development of this mixture, which occurs very slowly over time. The degree of crystallization of the SCM is directly related to the SCM/lime reactivity. MK exhibits a low degree of crystallization that leads to high reactivity with lime; fly ash, meanwhile, has a higher degree of crystallization, so it requires a longer reaction time.
The amount of heat in SL-30+MK-15 is reduced by 13% over the amount in the Control mixture within a week. This reduction in HoH may be attributed to the limited amount of CH formed in the ternary mixtures. That is, two pozzolanic materials may
34

compete for CH. In turn, this deprivation may result in a relatively slow rate of HoH and a reduction in the total cumulative amount of heat released. The reduction in HoH is not fully explained by the CH content alone but appears to be correlated with the Ca/(Al+Si) ratio.
Mechanical Properties and Durability Results Based on the results from Section 2.1 and the optimal MK replacement level determined from the Phase-I study (Chorzepa et al., 2017), a total of 19 mixtures are studied. Proportions for these mixtures appear in the Phase-I report.
Three MK (designated as `1', `2', and `3') and two slag (designated as `a' and `b') products are evaluated. MK1 is sourced from Sandersville, Georgia; MK2 is sourced from Aiken, South Carolina; and, MK3 is sourced from Sandersville, Georgia. All MK products used in this study are high-reactivity MKs that conform to ASTM C 618. The consensus within the literature is that a high-reactivity MK contains SiO2 + Al2O3 + Fe2O3 90% by weight. A review of the physical and chemical characteristics of the MKs used in this study can be found in (Chorzepa et al., 2017).
Two Grade 120, commercially available slag products were used in this study. The chemical composition and physical characteristics of these can also be found in Section 3.2.2. Table 5 presents a summary of findings from binary MK mixtures, while Table 6 provides a summary of findings from binary slag mixtures and the ternary mixtures.
35

Mechanical Durability Dimensional Stability

Table 5 Summary of binary MK performance.

Compression (28-day) Split-Cylinder Tension MOR Ed RCPT Permeability Sulfate Resistance ASR Resistance CTE Shrinkage

MK1 10% 17% 18% -10% -2% -67% F F 4% 3%

15% 29% 30% 38% -4% -79% P P 12% 0%

20% 44% 14% 20% -4% -65% P P 6% -10%

MK2 10% -9% -8% -1% -12% -38% F F 4% -7%

15% 19% -1% -16% -1% -75% F P 6% -11%

20% 6% 3% 1% -9% -75% F P 3% -19%

Note: F = Fail and P = Pass.

MK3 10% 21% 7% 5% 0% -74% F P 12% -9%

15% 25% 0% 5% -6% -81% P P 18% -15%

20% 15% 13% 6% -9% -81% P P 18% -35%

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Table 6 Summary of alternate binary and ternary SCM performance.

Binary

Mechanical

Compression (28-day)

Split-Cylinder Tension

MOR

Durability

Ed RCPT Permeability

Sulfate Resistance

ASR Resistance

Dimensional Stability CTE

Shrinkage

FA-45
-51%
-24%
-23%
-28% 42% -
P P -2%
10%

SLa-30 -2%
-15% 4% 3% 4% -
F F 3%
0%

SLb-30 18% 17% 35% 1%
-48% -
F F 7%
-17%

Teranary MK1-15 _SLa-30 10% 1% 0% -12% -74% -
P P 1%
-28%

MK1-15 _SLb-30
-9% -4% -8% -22% -83%
-
P P 4%
-10%

MK2-15 _SLa-30
-8% -8% -21% -15% -69%
-
P P 4%
-21%

MK2-15 _SLb-30
-10%
31% -25% -15% -85%
-
P P 7%
-27%

MK3-15 _SLa-30
0% 11% -15% -13% -84% -
P P 4%
-28%

MK3-15 _SLb-30
-4% -4% -5% -13% -85%
-
P P 5%
-21%

Note: F- Fail and P Pass.

37

Fresh Properties Table 7 shows the fresh concrete properties for all concrete mixtures. Slumps ranged from 1 inch to 10 inches (25 mm250 mm), and air contents typically ranged from 2.6%5.5% with a single outlier of 8.5% for MK2-10. Temperatures are generally within acceptable limits, with two or three nearing the upper 80s F (30 C32 C).

Table 7 Fresh concrete properties of mixtures.

Mixture Code
Control MK1-10 MK1-15 MK1-20 MK2-10 MK2-15 MK2-20 MK3-10 MK3-15 MK3-20 SLa-30 SLb-30 FA-45 MK1-15_SLa-30 MK2-15_SLa-30 MK3-15_SLa-30 MK1-15_SLb-30 MK2-15_SLb-30 MK3-15_SLb-30

Slump
in mm
2.5 64 8.5 216 1.3 32 2.0 51 3.0 76 1.5 38 2.0 51 6.5 165 3.8 95 1.5 38 1.0 25 1.0 25 6.0 152 10.0 254 1.8 44 9.0 229 9.0 229 3.8 95 2.0 51

Air Content(%)
4.1% 5.5% 3.8% 3.6% 8.5% 3.9% 3.6% 3.5% 3.1% 2.6% 4.3% 3.0% 0.0% 4.5% 3.9% 4.5% 3.5% 3.8% 5.0%

Unit Weight

pcf
146.4 147.8 144.4 143.4 144.2 149.8 144.8 144.4 144.0 144.2 136.8 146.8 146.0 140.6 141.4 136.4 144.6 143.6 144.8

kg/m3
2345 2367 2313 2297 2310 2399 2319 2313 2307 2310 2191 2351 2339 2252 2265 2185 2316 2300 2319

Temperature

F

C

73.0

22.8

75.7

24.3

73.4

23.0

66.6

19.2

82.7

28.2

59.7

15.4

75.2

24.0

78.1

25.6

78.8

26.0

84.6

29.2

68.2

20.1

82.4

28.0

86.7

30.4

84.9

29.4

73.9

23.3

75.6

24.2

83.7

28.7

88.2

31.2

80.1

26.7

38

Binary Metakaolin Hardened Properties Hardened properties of binary concretes and mortars that contain MK are presented. These include mechanical properties, durability properties, and the dimensional stability of these mixtures.
Mechanical properties MK products varied widely in their effect on compressive strength in binary mixtures. MK1 showed a systematic increase in compressive strength with increasing levels of replacement; the highest compressive strength,11,170 psi (77 MPa), occurred at 28 days by MK1-20. Compressive strengths for all replacements were 17%44% higher than that of the Control mixture at 28 days. Strength increase rates from 17 days were higher than those of the Control mixture for the 15% and 20% replacement levels, and the 1-day strengths for all replacement levels averaged 28% (580 psi or 4 MPa) higher than that of the Control mixture. Concretes incorporating MK2 saw an optimal 28-day compressive strength of 9,240 psi (64 MPa) at 15% replacement, which was 19% higher than that of the Control mixture. While MK2-20 also saw higher 28-day compressive strengths, MK2-10 saw a 7% reduction in compressive strengths and showed a lower rate of strength gain after one day of curing compared to the Control mixture. At the same time, the 15% and 20% replacement levels saw higher rates of strength gain compared to the Control mixture between 1 and 7 days. Overall, strength gains for MK2 ranged between 6%19%. MK3 performed consistently across all replacement rates, with its highest 28-day strength of 9,700 psi (67 MPa, a 21% increase) attributed to the 15% replacement level. MK3-15 also showed a notable 43% higher compressive strength than that of the Control mixture at 1 day of age. Regardless of replacement rate, MK3 showed no lower than a 15% increase in
39

compressive strength over the Control mixture at 28 days. Overall, only one mixture (MK210) did not exhibit a higher 28-day compressive strength than that of the Control mixture. For the rest of the mixtures, increases ranged between 6% and 44%. A graphical representation of the compressive strength evolution of the binary MK mixtures appears in Figure 17 (a-d).
The split-cylinder tensile strength of the Control mixture was 420 psi (2.88 MPa), and the Modulus of Rupture (MOR) was 710 psi (4.90 MPa). MK1-15 recorded both the highest split-cylinder tensile strength and MOR, 30% and 38% higher than those of the Control mixture, respectively. Only one test of tension for MK1, MK1-10, produced a tensile value of 10% less than that of the Control mixture. Otherwise, MK1 saw splitcylinder tensile strength increases between 14%30% and increases of MOR between 20%38%. MK2-20 recorded split-cylinder and MOR values similar to those of the Control mixture, while decreases in strength for the other two replacement levels, MK2-10 and MK2-15, were as high as 16% (MK2-15 MOR) when compared to the Control mixture. All measures of tension for MK3 were the same or higher than those of the Control mixture. The optimal replacement level for this MK product was 20%, with the split-cylinder tension 13% higher and the MOR 6% higher than the Control mixture. Overall, MK3 saw split-cylinder strength increases between 0%13%, and MOR increases between 5%6%. Finally, MK1 saw the most dramatic increases in tensile strength and indicated a clear optimal replacement level of 15%. MK3, meanwhile, saw moderate increases in strength that were consistent among replacement levels. MK2, on the other hand, caused a reduction in strength. A bar graph comparing the split-cylinder and MOR tensile strengths of the binary MK mixtures appears in Figure 18.
40

For the Control mixture, the dynamic measure of Young's modulus of elasticity was 5,440 ksi (37.5 GPa). Decreases in this measure across all replacement levels of MK1, MK2, and MK3 were observed, excluding MK3-10. Decreases ranged from 2%4% for MK1 concretes, 1%12% for MK2 concretes, and 0%9% for MK3 concretes. Figure 19 displays these values in a bar chart.

(a) MK1

(b) MK2

(c) MK3

(d) 28-day highest strength mixtures

Figure 17 Compressive strength evolution for binary MK concrete mixtures.

41

Figure 18 Tension results for binary MK concrete.
Figure 19 Dynamic MOE for binary MK concrete. 42

Durability The Rapid Chloride Permeability Test (RCPT) indicated that all binary MK mixtures achieved lower permeability to chloride ions compared to the Control mixture. All MK1 mixtures belong to the `very low' permeability class (i.e., less than 1,000 C passed), with MK1-15 displaying the lowest permeability at 588 C. MK2 required a 15% or greater replacement level before reaching the same permeability class; MK2-10 passed 1,718 C while MK2-15 and MK2-20 passed 693 C and 697 C, respectively. MK3 achieved the lowest permeability, with its lowest at 496 C passed by MK3-20. However, other MK3 replacement levels performed similarly, with the highest recorded at 712 C. Overall, all MK concretes were classified as having a `very low' permeability, excluding the MK2-10 mixture. Figure 20 provides a visual representation of these RCPT results along with indicators for permeability classes. Notably, while MK2-10 passed the most charge of any binary MK mixture, it was classified in a lower permeability class than the Control mixture.
The 6-month (168 days) expansion criterion set in ASTM C 1012 is 0.10% of the original length of the mortar bar. The Control mixture exceeded this expansion limit and ended the testing period with a total expansion of 0.47%. All mixtures with a 10% replacement failed to meet the expansion criterion. Most notably, mortar bars for mixtures MK2-10 and MK2-15 deteriorated before they could reach the end of the testing period (91 days and 112 days, respectively). MK2 and MK3 sufficiently limited expansion at replacement levels of 15% and 20%. The systematic increase in sulfate resistance for increasing replacement levels can be seen in Figure 21.
According to ASTM C1567, an SCM combination has sufficiently mitigated expansion due to Alkali-Silica Reactivity (ASR) if it expands less than 0.10% of its original
43

length at the end of a 14-day testing period. The ultimate expansion of the Control mixture was 0.17%. A consistent, systematic trend of increased ASR resistivity can be seen as binary MK replacement levels increase. For MK1 and MK2, a 15% replacement level was required to meet this expansion criterion. MK3 was the only MK that was able to meet this criterion at all replacement levels, though MK3-10 expansion was exactly 0.10% at the end of the 14-day testing period. MK1-15 and MK3-15 performed similarly, with an ultimate expansion of 0.04%. At the 20% replacement level, MK1-20 achieved the lowest ultimate expansion at below 0.02%, while MK3-20 was just over 0.02%. A time history of these expansions can be seen in Figure 22.
Figure 20 RCPT results for binary MK concrete.
44

Figure 21 Sulfate expansion of binary MK mortars.
Figure 22 ASR expansion of binary MK mortars. 45

Dimensional stability Figure 23 indicates that the ultimate drying shrinkages of binary concretes containing MK were predominantly lower than that of the Control mixture. For the Control mixture, the 224-day drying shrinkage was 0.048%. One mixture, MK1-10, was slightly larger at 0.049%. For each product, the overall drying shrinkage decreased systematically with increasing replacement levels. For MK1, these values decreased from 0.049% to 0.039%. For MK2, shrinkage values decreased from 0.045% to 0.039%. Finally, MK3 concrete mixtures had shrinkage values that decreased from 0.044% to 0.031%, and MK3-20 showed the lowest drying shrinkage in this study.
The Coefficient of Thermal Expansion (CTE) of the Control mixture was 5.34x106 in/in/F (9.61x10-6 mm/mm/C). All binary concrete mixtures containing MK exhibited higher CTEs than the Control mixture. MK1 saw a high of 5.96x10-6 in/in/F (10.72x10-6 mm/mm/C) at the 15% replacement level and a low of 5.53x10-6 in/in/F (9.95x10-6 mm/mm/C) at the 10% replacement level. MK2 generally saw lower CTEs compared to MK1 and MK3, and had the lowest binary CTE at 5.5x10-6 in/in/F (9.88x10-6 mm/mm/C) for MK2-20. Finally, MK3 concretes consistently observed the highest CTEs, ranging from 6.0x10-6 in/in/F to 6.3x10-6 in/in/F (10.80x10-6 mm/mm/C to 11.38x10-6 mm/mm/C). MK1 and MK2 exhibited peak CTEs at the 15% replacement level. However, MK3 saw no reduction in CTE from the 15% replacement level to the 20% replacement level. A bar graph of these results can be seen in Figure 24.
46

Figure 23 Drying shrinkage of binary MK concrete.
Figure 24 CTEs of binary MK concrete. 47

Ternary and Alternate Binary SCM Hardened Properties The hardened properties of alternate binary SCM and ternary SCM mixtures are discussed. These include mechanical properties, durability properties, and the dimensional stability of these mixtures.
Mechanical properties Of the two binary mixtures including slag or fly ash, only one mixture achieved a 28-day strength higher than that of the Control mixture. SLb-30 exhibited a 28-day compressive strength of 9,222 psi (64 MPa), an increase of 18% over the Control mixture. Mixtures SLa-30 and FA-45 were 2% and 51% weaker in compression compared to the Control mixture, respectively. The rate of strength gain was relatively similar between the two binary slag mixtures, though SLb-30 was stronger than SLa-30 by slightly over 1,300 psi (9 MPa) at 1 day of age. This was nearly the same difference in strength at 28 days of age.
Of the ternary mixtures, only one mixture had a higher 28-day compressive strength than the Control mixture: SLa-30+MK1-15 finished with a compressive strength of 8,570 psi (59 MPa), 10% higher than that of the Control mixture. SLa-30+MK3-15 finished with a compressive strength similar to that of the Control mixture, at 7,770 psi (54 MPa). For all ternary concretes including SLa, 1-day strengths were similar or less than the 1-day strength of the Control mixture, ranging from 715 psi-1010 psi (5 MPa-7 MPa). Apart from SLa-30+MK1-15, 7-day strengths for concretes including SLa were lower than the 7-day strength for the Control mixture, as well. However, after seven days, all SLa ternary concretes gained compressive strength at a higher rate than the rates exhibited by SLb ternary concretes and the Control concrete. By contrast, ternary concretes with SLb did not suffer lower 1-day strengths (1,730 psi-2,110 psi, 12 MPa-14.5 MPa), though they were
48

still lower than that of the Control mixture. Moreover, ternary concretes consisting of SLb exhibited the highest strength gain rate from one to seven days but saw a less dramatic strength gain after seven days of age. Overall, excluding SLa-30+MK1-15, 28-day strengths for ternary concretes ranged from 6,970 psi-7,769 psi (48 MPa-54 MPa). Strength evolutions for all mixtures other than binary MK mixtures can be found in Figure 25.
Binary slag mixtures were, overall, stronger in tension compared to the Control mixture. SLa-30 produced a splitting tensile strength 15% lower than that of the Control mixture, while SLb-30's was 17% higher than the Control mixture. MOR values for these concretes were both higher than the Control mixture: 740 psi and 958 psi (5.1 MPa and 6.6 MPa), respectively. The fly ash mixtures saw a strength reduction in splitting-tension and MOR of 24% and 23%, respectively. Ternary SCM concretes typically displayed lower tensile strength compared to the Control mixture; however, SLa-30+MK1-15 performed similarly to the Control mixture for both split-tension and MOR. Further, apart from the SLb-30+MK2-15 split tension results, ternary concretes incorporating MK1 and MK3 appeared to have higher tensile strengths when compared to ternary concretes incorporating MK2. Meanwhile, the choice of slag product does not seem to affect the tensile strength of concrete in ternary mixtures. The tensile strength results of binary slag and fly ash concretes as well as ternary concretes are found in Figure 26.
Young's modulus for each of the binary slag concretes was higher than that of the Control mixture, while all other mixtures saw values lower than that of the Control mixture. Increases were on the order of 150 ksi and 60 ksi (1 GPa and 0.4 GPa) for SLa-30 and SLb30, respectively. The greatest reduction in Young's modulus was exhibited by the fly ash mixture with a decrease of 28% from the modulus of the Control mixture. There were no
49

obvious trends among MK or slag products for the ternary concrete mixtures, and reductions in dynamic modulus, Ed, ranged from 12%22% with an average reduction of 811 ksi (5.6 MPa). Young's modulus values for binary slag and fly ash mixtures and the ternary SCM mixtures are listed in Figure 27.

(a) alternate binary SCM concrete

(b) ternary SCM concrete

Figure 25 Compressive strength evolution for alternate binary SCM and ternary SCM concrete.

50

Figure 26 Tensile strength of alternate binary SCM and ternary SCM concrete.
Figure 27 Dynamic MOEs of alternate binary SCM and ternary SCM concrete. 51

Durability Figure 28 shows that only one of three alternate binary SCM concrete mixtures were able to reduce chloride-ion permeability below the reduction afforded by the Control mixture. SLa-30 performed similarly to the Control mixture, while FA-45 almost reached the `high' penetrability classification. SLb-30, however, was effective in reducing the total charge passed to 1,440 C, thereby earning a `low' penetrability classification. All ternary SCM concretes fell below 1,000 C passed, and of those, four passed under 500 C. Penetrability classes and results for non-MK binary SCM concretes and ternary SCM concretes can be found in Figure 28.
Fly ash was the only SCM other than MK to sufficiently mitigate mortar expansion for the entire 6-month testing period. In fact, expansion of the binary slag mortars was more accelerated than the expansion of the Control mixture; this was especially so for the mortar incorporating SLa. All ternary mixtures were able to mitigate sulfate expansion during the 6-month window, and they typically resulted in less than 0.06% expansion. These results are presented in Figure 29.
As with the sulfate tests, binary slag mortars at a replacement level of 30% were not sufficient to limit expansion below acceptable limits (expansions of 0.11% and 0.12%). The binary fly ash mortar exhibited expansion similar to that of the ternary mixtures. All ternary mortars resulted in expansions less than 0.03%. Figure 30 presents these results.
52

Figure 28 RCPT results for alternate binary SCM and ternary SCM concrete.
Figure 29 Sulfate expansion of alternate binary SCM and ternary SCM mortars. 53

Figure 30 ASR expansion of alternate binary SCM and ternary SCM mortars.
Dimensional stability As evident from Figure 31, the fly ash binary mixture showed the highest drying shrinkage among all the mixtures, with the 224-day drying shrinkage of 0.058%. The 224day drying shrinkage of the SLb-30 binary mixture was 0.04%, which was lower than the Control mixture by 17%. Meanwhile, SLa-30 mixture resulted in a similar shrinkage to that of the Control mixture. The ultimate drying shrinkage of ternary concretes containing slag and MK were predominantly lower than the shrinkage of the Control mixture. The SLa-30+MK1-15 and SLa-30+MK3-15 had the lowest 224-day drying shrinkage of 0.034%, which was about 28% lower than the Control mixture.
Figure 32 indicates that the binary fly ash concrete exhibited a 2% lower CTE than that of the Control mixture. SLa-30 and SLb-30 varied widely from one another at 3% and 7% higher CTE compared to the Control mixture, respectively. The latter was the highest
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CTE seen outside of the binary MK concretes. SLa-30+MK1-15 saw the lowest CTE in the ternary group with a value of 5.40 in/in/F (9.73x10-6 mm/mm/C), an increase of 1% from that of the Control mixture. SLb-30+MK2-15 saw the highest CTE in the ternary group with a CTE of 5.70x10-6 in/in/F (10.25x10-6 mm/mm/C), an increase of 7% over the CTE of the Control mixture. As a group, the ternary SCM concretes averaged a CTE of 5.53x10-6 in/in/F (9.93x10-6 mm/mm/C), an increase of 3% compared to the CTE of the Control mixture. CTE results are presented in Figure 32.
Figure 31 Drying shrinkage of alternate binary SCM and ternary SCM concrete.
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Figure 32 CTEs of alternate binary SCM and ternary SCM concrete.
Discussion This section discusses the results presented in Section 2.2 in the context of existing research. Binary mixtures including MK will be utilized to discuss important differences between the MK products. The performance of alternate binary SCM and ternary SCM mixtures will also be discussed.
Comparison of Binary Metakaolin Mixtures Contrary to expectation, not every MK product benefitted concrete when part of a binary mixture. In particular, MK2 was inconsistent with respect to its effect on the mechanical strength of concrete. Moreover, a clear difference was observed in the durability test results of MK2 and the other MK products. The expansion of MK2-10 and MK2-15 mortars in the sulfate solution were the most aggressive in the entire testing program. The expansion
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of MK2-20 in the sulfate solution most closely resembled the expansion of the other two products at a 10% replacement level. Figure 33 shows disintegration of the MK2-10 mortar bars as a result of deleterious expansion.

Figure 33 Deleterious expansion by sulfate attack of MK2-10 mortar bars.

Table 5 Repeated Summary of binary MK performance.

Mechanical Durability Dimensional Stability

Compression (28-day) Split-Cylinder Tension MOR Ed RCPT Permeability Sulfate Resistance ASR Resistance CTE Shrinkage

MK1 10% 17% 18% -10% -2% -67% F F 4% 3%

15% 29% 30% 38% -4% -79% P P 12% 0%

20% 44% 14% 20% -4% -65% P P 6% -10%

MK2 10% -9% -8% -1% -12% -38% F F 4% -7%

15% 19% -1% -16% -1% -75% F P 6% -11%

20% 6% 3% 1% -9% -75% F P 3% -19%

MK3 10% 21% 7% 5% 0% -74% F P 12% -9%

15% 25% 0% 5% -6% -81% P P 18% -15%

20% 15% 13% 6% -9% -81% P P 18% -35%

With each product, the replacement levels that achieved the highest 28-day compressive strength also achieved the highest 7-day compressive strength. Overall, variation was low in these 7-day strengths. Figure 17 shows this tight clustering of 7-day strengths from all products at their optimal replacement levels (54 MPa-56 MPa). Notably, when these replacement levels were the same (i.e., for MK2-15 and MK3-15), strength

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gain rates were very similar at all ages. Only when the optimal replacement is at 20% (MK1-20) does a higher compressive strength gain become evident after 7 days of age. The tight clustering of the 7-day compressive strength values is considered to be the result of similar oxide composition (see Section 3.2.1.1); this is not a poignant statement, as these MKs are being tested specifically because they are commercially-available high-reactivity metakaolins (HRMs) (Al2O3 + SiO2 + Fe2O3 90%). At the same time, because the majority of the pozzolanic reaction is completed between 7 and 14 days of age, comparable 7-day compressive strengths may indicate similar CH consumption and C-S-H formation rates across all MKs when their optimal replacement level is used (Wild et al., 1996). While this explanation would be consistent with MK1-20 showing additional strength gain between 7 and 28 days, (i.e., additional pozzolanic activity between 714 days), it is unknown why MK1 displays a higher optimal replacement level than that of the other two MKs.
Optimal replacement level trends in compressive strength tests did not translate to tensile strength results. MK1 saw optimal tensile strength at 15% replacement, while MK2 and MK3 reached their optimal strengths at 20% replacement. In addition, compared to the measures of tensile strength for MK3, larger variations were observed for MK1 and MK2 between replacement levels. This is consistent with the compressive strength findings, where MK3's compressive strength demonstrated less variation between replacement levels than the variation observed for the other two products. In fact, MK3 mixtures were more consistent across replacement levels than either of the other two MKs in all measures except the dynamic measure of Young's modulus. Here, MK3 saw the largest variation among any MK.
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MK1 and MK3 were consistent in their ability to decrease permeability and increase resistance to chemical attacks. The inclusion of these MKs at all replacement levels resulted in very low RCPT permeability classifications, and beyond 15% replacement of both products sufficiently mitigated deleterious expansion in aggressive solutions. In addition, MK2 was able to achieve the same permeability classification as the other two MKs at or above a 15% replacement level, sufficiently mitigating ASR expansion only.
MK2 had the highest fineness of the three MKs, and a similar oxide composition. Increased fineness of MK has been shown to increase the rate of strength gain as well as the overall 28-day strength of concretes (Justice & Kurtis, 2007). Yet, the inclusion of MK2 does not result in higher performance across all hardened concrete tests in this study when compared to the other two MKs. Most dramatically, MK2-10 and MK2-15 deteriorated in sulfate solution more than the Control mixture. Similar performance has only been recorded once in the literature, using a MK with Al2O3 + SiO2 + Fe2O3 = 85% and a loss on ignition (LOI) of 14% (Torres Agredo et al., 2008). In fact, Table 5 shows that MK2 exhibits a significantly reduced performance for all replacement levels.
Given this information, the following are possible explanations for MK2's poor performance:
MK2's high fineness resulted in large agglomerations which were not properly deflocculated during the batching of the concrete. o This would explain tensile strengths lower than that of the Control mixture but not the inordinate deterioration of the sulfate mortar bars.
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MK2's alumina and silica contents were not amorphous, leading to an incomplete dehydroxylation of the MK (see (Brindley & Nakahira, 1957; Murray & Lyons, 1955)). o This would explain the mechanical performance as well as the rapid destruction of MK2 sulfate mortar bars, as the non-amorphous kaolin would act as inert material. o For compression and permeability, inert kaolin would still contribute to particle packing (Ramezanianpour, 2014), and the alumina content has been shown to increase chloride-binding capacity (Badogiannis et al., 2015; Wang et al., 2014). Moreover, the fine material would still provide additional nucleation sites for cement hydration (Wild et al., 1996). o This does not explain why the optimal replacement level for tensile strength was 20%.
All concretes containing MK exhibit increased expansion due to temperature change, as indicated by CTE values greater than that of the Control mixture. Concretes typically achieved a peak CTE value at 15% replacement. To date, no known research has been published on the CTE values of MK concretes. Existing research has concluded that the inclusion of fly ash, slag, and silica fume (SF) reduces the CTE of cement pastes (Shui et al., 2010). The mechanism by which the inclusion of SF reduces CTE is different from that of fly ash and slag inclusion: SF reduces CH contents, which have a higher CTE than that of plain cement pastes, while fly ash and slag reduce CTE by CH consumption and increased porosities, as an increase in porosity is expected to decrease CTE. This finding would support an increase in CTE by inclusion of MK only if the CTE reduction by CH
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consumption is less than the increase in CTE due to the reduction of porosity. Temporarily ignoring MK2 and its poor performance, this explanation is supported by the finer MK (MK1) achieving lower CTE values than those of MK3, since finer MK likely exhibits a higher CH consumption with similar porosities (see the RCPT results). The deleterious results of jointed concrete pavements with CTE values higher than 5.5 in/in/F (10x10-6 mm/mm/C) have been reported (Sabih & Tarefder, 2016).
Reduction in drying shrinkage with the inclusion of MK is supported by the literature (Brooks & Johari, 2001; Gleize et al., 2007; Wild et al., 1998). Some researchers have reported a systematic decrease in drying shrinkage with increasing replacement levels of MK (Gleize et al., 2007; Gneyisi, Gesolu, & Mermerda, 2008), while others have reported no observable benefit from higher replacements (Brooks & Johari, 2001).
Comparison of Ternary and Alternate Binary SCM Mixtures Overall, ternary mixtures' mechanical strengths were equal to or just below those exhibited by the Control mixture. Only one mixture, SLa-30+MK1-15, managed to obtain a 28-day compressive strength higher (10%) than that of the Control mixture.
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Table 6 Repeated Summary of alternate binary and ternary SCM performance.

Binary

Mechanical

Compression (28-day)

Split-Cylinder Tension

MOR

Durability

Ed RCPT Permeability

Sulfate Resistance

ASR Resistance

Dimensional Stability CTE

Shrinkage

FA-45
-51%
-24%
-23%
-28% 42% -
P P -2%
10%

SLa-30 -2%
-15% 4% 3% 4% -
F F 3%
0%

SLb-30 18% 17% 35% 1%
-48% -
F F 7%
-17%

Teranary MK1-15 _SLa-30 10% 1% 0% -12% -74% -
P P 1%
-28%

MK1-15 _SLb-30
-9% -4% -8% -22% -83%
-
P P 4%
-10%

MK2-15 _SLa-30
-8% -8% -21% -15% -69%
-
P P 4%
-21%

MK2-15 _SLb-30
-10%
31% -25% -15% -85%
-
P P 7%
-27%

MK3-15 _SLa-30
0% 11% -15% -13% -84% -
P P 4%
-28%

MK3-15 _SLb-30
-4% -4% -5% -13% -85%
-
P P 5%
-21%

For comparison, the average compressive strength increase over the Control mixture's compressive strength for all binary MK mixtures was 18% (ranging from -9% to 44%). SLa-30+MK1-15 also had the highest tensile strength of the ternary group, with an MOR equal to that of the Control mixture. Although the ternary mixtures outperformed binary concretes incorporating SLa, concretes incorporating SLb saw higher compressive (18% higher than that of the Control mixture) and tensile (MOR 35% higher than that of the Control mixture) strengths than the strengths exhibited by all ternary mixtures. Moreover, SLb-30 exhibited the highest tensile strength of all concretes tested.
The early-age strength properties of the ternary mixtures appear to be primarily dependent on the slag product used, with the SLb concrete mixtures recording higher 1day and 7-day strengths. Ternary mixtures incorporating SLa and SLb exhibited nearly the same strengths as the SLa and SLb binary mixtures, respectively. The difference in compressive strengths between concretes incorporating SLa and SLb continued to be visible up to seven days, as Figure 25 shows. After this, the compressive strengths of all ternary mixtures approached that of the Control mixture.

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Both MK and slag react pozzolanically with CH in ternary mixtures, which promotes optimal CH consumption and higher paste densities. This finding is evidenced by the durability results presented above, but it does not necessarily ensure higher mechanical strengths, as unreacted SCM is most likely present due to competing pozzolanic activity (Li et al., 2010). This explanation is supported by Khatib & Hibbert's (2005) study, which found that as the level of MK inclusion increased, optimal compressive strengths were found by reducing slag contents. Although slag is also a latent hydraulic material, its CaO content is less than that of ordinary Portland cement; thus, less CH is produced during hydration when slag replaces a portion of cement. In short, in ternary mixtures incorporating 30% slag and 15% MK, the slight reduction in compressive strength is a result of less CH for pozzolanic activity and more unreacted pozzolan. The increased density of the paste matrix and additional C-S-H via the pozzolanic reaction compensate for the unreacted material.
The most substantial benefits of the ternary mixtures were seen in the durability tests and most likely are the result of high CH consumption. All ternary mixtures indicated very low permeabilities. Five total mixtures passed less than 500 C, and ternary mixtures accounted for four of these five. The ternary mixtures including SLb recorded the lowest permeability, with a study low of 419 C recorded for a ternary mixture combining SLb with MK3. In addition, sulfate expansion of less than 0.60% was achieved by only one binary mortar mixture (MK1-20). By contrast, five of the six ternary mortars finished the 6-month testing period under this value. Similarly, all six ternary mortars met ASR expansion criteria. This indicates that, although durability performance varied widely
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within binary slag and binary MK mortars (see Figures 21-23 and Figures 28-30), ternary mixture durability was consistently high regardless of product combinations.
All ternary concrete mixtures exhibited higher CTE values than that of the Control mixture; however, they were much lower than those of the binary MK mixtures. As mentioned, increased porosities in fly ash and slag concrete mixtures have been correlated with decreases in paste CTEs (Shui et al., 2010). This is a geometrical property. Only when high CH consumption exists (using SF) do low-porosity pastes exhibit CTEs lower than that of the Control mixture. This behavior is attributed to C-S-H, with a low CTE, replacing CH, with a higher CTE, and having a dominant effect. Figure 28 indicates that ternary concretes incorporating SLa have higher penetrability, and by inferred extension, higher porosities, than SLb concrete mixtures on average. Also, as Figure 32 illustrates, SLa concrete mixtures exhibit lower CTE values than SLb mixtures on average. It is hypothesized that a reduction in porosity leads to higher CTE values in SLb ternary blends. Further, the CTEs are higher for ternary blends than for the Control mixture but significantly lower than the CTEs of binary MK concrete mixtures, which would most likely have lower porosities than those of ternary concrete mixtures. Overall, CTEs of ternary concrete mixtures were well below the 5.5x10-6 in/in/F (10x10-6 mm/mm/C) limit for good performance in jointed concrete pavements (Sabih & Tarefder, 2016). Table 6 provides a summary of alternate binary SCM and ternary SCM mixture performance.
Conclusions and Recommendations from Section 2 This section further adds to the discussion presented in Section 2.3. Important results are summarized, and recommendations are made for the appropriate use of MK in binary and ternary concrete systems. Shortcomings of this study and future work are also presented.
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Summary of Findings Table 5 provides a summary of the performance of binary MK mixtures, while Table 6 provides a similar summary for the performance of alternate binary SCM and ternary SCM mixtures. The key findings in this study are as follows:
All concretes incorporating MK as a cement replacement require a high dosage of superplasticizer ( 4 mL/kg of cementitious material or 6.1 oz./cwt), with higher dosage requirements at higher MK replacement levels.
Binary usage of MK results in increased mechanical strengths, although the most significant increases are in compression. Increases up to 44% at 28 days of age were observed.
Binary usage of MK results in increased chloride-ion penetrability and resistance to sulfate and ASR chemical attacks. A replacement level of 15% will ensure adequate resistance, although future work should include ASR tests with reactive aggregates.
Binary usage of MK resulted in concretes with large CTE values and decreased drying shrinkage. Risk of crack development while using MK will likely depend on the type of concrete application (e.g., pavement, mass concrete, prestressing, etc.). A time history of CTEs should be studied so that expansion characteristics during hydration can be modeled.
MK2 was an obvious outlier and did not perform well against sulfate attack. Caution should be exercised in choosing which MK products to put on Qualified Products List (QPL). Recommendations will be discussed in the next section, 2.4.2.
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Binary replacement mixtures containing a pozzolanic material such as MK (15%) offer no significant advantage in reducing HoH, although compressive strength increases up to 44% on the 28th day.
The pozzolanic reaction of the binary mixture (MK15) starts after two days and mainly occurs between two and five days.
Ternary concrete mixtures using slags and MKs (30% slag+15% MK) tend to perform similarly to one another and the Control mixture in both compression and tension at 28 days of age. Early-age strength characteristics of ternary mixtures resemble the early-age strength characteristics of the 30% mixture using the same slag.
Ternary concrete mixtures using slags and MKs exhibit very high resistance to chemical attack and very low chloride-ion penetrability. All combinations of commercially available products performed similarly to one another.
Ternary concrete mixtures using slags and MKs result in increased CTE values, although these values are much lower than the CTEs for binary MK mixtures. Values were near the threshold of 5.5x10-6 in/in/F (10x10-6 mm/mm/C) reported to be deleterious in jointed concrete pavements. Drying shrinkage was lowered from the shrinkage of the Control mixture for these mixtures and was on average lower than the shrinkage of the binary MK mixtures. As with the binary MK mixtures, a time history of CTEs should be studied if ternary mixtures are to be used in mass concrete.
The optimal weight ratio of pozzolans used in ternary replacement mixtures is 2 slag:1MK when a 45% ternary replacement is considered.
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The presence of two pozzolanic materials including high silica and alumina contents in ternary replacement mixtures results in approximately 13% reduction in the total amount of heat within 7 days and about 10% strength gain by 28 days, relative to the Control mixture. The amount of heat generated in ternary mixtures is proportional to the Ca/(Al+Si) ratio.
The ternary replacement mixture of 30% slag and 15% MK results in a significant reduction in HoH, and its HoH is lower than that of the binary mixture with 45% slag replacement.
Ternary replacements of cement with combined slag and MK significantly reduce HoH and enhance durability properties; thus, they could possibly alleviate the thermal cracking potential of concrete.
Recommendations for Usage Binary replacements of cement by MK should be used if high mechanical strengths (at any age) are desired for the following reasons:
MK provides similar compression benefits to SF (Duan et al., 2013; Gneyisi et al., 2012; Caldarone et al., 1994; Poon et al., 2006) but does not suffer from SF's dark coloration.
MK is also less expensive than SF, and quality can be ensured because it is not a byproduct.
The authors recommend that concretes not incorporate MKs as a binary replacement for cement in massive concreting operations or in pavements. Figure 24 shows the dramatic effect of some MK products on CTE. According to the authors, the thermal
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expansion evinced by these concretes under normal temperature fluctuations would quickly crack and degrade pavements and mass concrete.
Binary MK mixtures show dramatic benefits in resistance to chemical attack and durability as do ternary mixtures with slag. If mechanical strengths need only be similar to the Control mixture, it is recommended that a ternary mixture be used. Ternary mixtures see benefits beyond those of binary MK mixtures:
Lower CTEs Lower HoHs Increased resistance to chemical attack Reduced permeability
Future Work Further research should evaluate the following:
The dispersion of high-fineness, plate-like MK in ready-mixed-sized concrete batching. Recommendations are provided by the Silica Fume Association (SFA, 2019).
The pozzolanic reactivity (ASTM C311) of various commercially available MKs in the U.S., and its effect on concrete performance. The authors affirm that the commonly specified minimum of an 85% reactivity index (Florida, Texas) is insufficient to ensure quality. Particular attention should be paid to ensure that MKs appearing on QPLs have a high fraction of kaolinite converted to MK (amorphous, or glassy alumina and silica). Minimum contents should be set by future studies.
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Time-dependent CTEs of ternary mixtures. These mixtures have been shown to reduce HoH, and low CTEs during the hydration period would prove the reliability and durability of these mixtures for mass concreting.
The relationship between MOE by forced resonance method and static MOE measurements for binary and ternary MK concrete.
The relationship between HoH and pozzolanic activity (e.g., CH consumption). X-ray diffraction and scanning electron microscope tests for ternary mixtures.
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3. EXPERIMENTAL INVESTIGATION OF THE HEAT OF HYDRATION AND TEMPERATURE CHANGES
This section starts with a detailed literature review of available guides and state DOT specifications for mass concrete structures. This section also presents an experimental study to quantify maximum temperatures in 17 mass concrete specimens. These specimens include different SCMs and various combinations of binary and ternary replacement mixtures. Section 3.2 presents the methodology and procedures for testing the specimens. Sections 3.3 and 3.4 present the results and analysis of the results, respectively. A summary of the literature review from the mass concrete standard specifications is presented in Appendix C.
Literature Review GDOT Special Provision to Section 500 (GDOT, 2013) has been approved by the Federal Highway Administration (FHWA) and is currently acceptable for any mass concrete project in Georgia. In light of the current provision, this section provides a literature review of ACI standards and other state DOT mass concrete specifications.
U.S. Mass Concrete Specifications and Guides American Concrete Institute specifications for structural concrete (ACI 301-16)
The ACI does not use specific size limits to define mass concrete. The characteristic that distinguishes mass concrete from other concrete elements is its thermal behavior, which may "cause a loss of structural integrity and monolithic action" (ACI 301-16, 2016). ACI 301-16 "Specifications for Structural Concrete" defines mass concrete as "any volume of structural concrete in which a combination of dimensions of the member being cast, the
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boundary conditions, the characteristics of the concrete mixture, and the ambient conditions can lead to undesirable thermal stresses, cracking, deleterious chemical reactions, or reduction in the long-term strength as a result of elevated concrete temperature due to heat of hydration." The following temperature limits apply for mass concrete placements:
The maximum temperature in concrete after placement shall not exceed 160 F (71.1 C).
The maximum temperature difference between the center and the surface of the placement (i.e., gradient temperature) shall not exceed 35 F (19.4 C).
For mass concrete placements, the ACI specification requires the use of hydraulic cement with moderate to low HoH (ASTM C150 Type I or Type II cement), or the use of Portland cement with fly ash or slag cement, or the use of both. No specific limits are stated for the percentage of cementitious materials used; however, the maximum percentage replacement by mass (i.e., 25% for fly ash conforming to ASTM C618 and 50% for slag conforming to ASTM C989/C989M) is specified for concrete assigned to Exposure Class F3. This class includes concrete exposed to severe freezing and thawing cycles in continuous contact with moisture and to deicing chemicals. For any mass concrete placement, the specifications typically require a thermal control plan by the contractor. This includes the following items:
Concrete mixture proportions Calculated or measured adiabatic temperature rise of concrete Upper limit for concrete placement temperature Calculated maximum temperature and temperature difference in placement
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Description of specific measures and equipment that will be used to ensure that the maximum temperature and temperature difference will not exceed specified limits
Drawing that shows locations for temperature sensors and a description of the equipment and procedures that will be used to monitor and log temperatures and temperature differences
Format and frequency of providing temperature data Description of curing methods and formwork removal procedures
The temperature and temperature difference within the concrete "shall be controlled from time of placement until time when the internal temperature has cooled from its maximum so that the difference between average daily ambient and internal temperatures is less than a specified temperature difference limit." To monitor concrete temperature, ACI recommends placing one temperature sensor at the mass placement center and another sensor at a depth of two inches from the center of the nearest exterior surface. Additional backup sensors need to be placed at each location. Finally, a temperature sensor must be placed in a shaded location for monitoring ambient on-site temperature.
ACI specifications also require mass concrete to be cured and protected for a minimum of seven days. The use of water curing is not recommended, though the following methods are: "ponding, continuous fogging or sprinkling, application of mats or fabric kept continuously wet, continuous application of steam kept under 150 F (65.6 C), application of sheet materials conforming to ASTM C171, and application of curing compound conforming to ASTM C309 or C1315." For surfaces not in contact with forms, one of the aforementioned curing methods is recommended.
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ACI guide to mass concrete (ACI 207.1R) This document (ACI 207.1R-05, 2012) covers the history of the development of mass concrete practice and a discussion of materials and concrete mixture proportioning, properties, construction methods, and equipment. Detailed guidance in proportioning mass concrete is presented in ACI 211.1 (Standard Practice for Selecting Proportions for Normal, Heavyweight, and Mass Concrete), mainly in Appendix 5 (ACI 211.1-91, 2009). Type II moderate heat cements are recommended for use in mass concrete placements as they generate moderate heat during hydration. Type II cement must be specified with the moderate heat option and contain no more than 8% tricalcium aluminate (C3A), a compound that contributes to early heat development. Type IV and low-heat cements are also recommended, although they are difficult to obtain and infrequently used in cement production today.
The ACI 207.1R recommends controlling the temperature of concrete by implementing the following measures to reduce thermal stresses and control cracks:
Control the cementitious material content and use suitable type of materials to lower the heat-generating potential of the concrete.
Pre-cool ingredients and post-cool the concrete to lower temperature. Protect the structure from excessive temperature differentials through construction
management.
The guide further recommends that temperature control measures for mass concrete placements can include a prudent selection of low-heat-generating cement systems, such as
using pozzolans,
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controling aggregate grading and the use of large-size aggregate in mixtures with low cement contents,
lowering the placement temperature by pre-cooling the aggregate and mixing water or using ice instead of mixing water,
using chemical admixtures to improve both fresh and hardened properties of concrete,
using appropriate block dimensions for placement and coordinating construction schedules with seasonal changes to establish lift heights and placing frequencies,
using special mixing and placing equipment to quickly place cooled concrete with minimum absorption of ambient heat,
post-cooling by circulating cold water through embedded piping, properly curing the surface, and insulating surfaces to minimize thermal differentials between the interior and
exterior of the concrete.
Lastly, the guide states that mass concrete should be water-cured for at least 14 days, or up to twice this amount of time if a pozzolan is used as one of the cementitious materials.
ACI technical report on mass concrete (ACI 207.2R) The ACI 207.2R report on "Thermal and Volume Change Effects on Cracking of Mass Concrete" (ACI 207.2R-07, 2007) presents a discussion of the effects of heat generation, restraint, and volume change on the design and behavior of mass concrete elements and structures. Discussion of various factors that influence mass concrete cracking and volume
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change is presented. What differs ACI 207.1R from ACI 207.2R is that the former is a general guide on mass concrete, whereas the latter provides additional information and detailed discussion on cement types and effects on heat generation, thermal issues, thermal properties, thermal property values for some mass concrete, factors influencing cracking, and example computations.
AASHTO and FHWA construction specifications Two specifications are noteworthy although they are not specific to mass concrete structures. The American Association of State Highway and Transportation Officials (AASHTO) (AASHTO LRFD, 2017) specify that the maximum temperature within concrete should not exceed 158 F (70 C) if a known potential for ASR or DEF exists. Otherwise, the maximum concrete temperature is 180 F (82 C). A maximum temperature of 160 F (71.1 C) is specified for precast concrete. The Standard Specifications (FP-14) for Construction of Roads and Bridges on Federal Highway Projects (FHWA FP-14, 2014) specifies temperature limits for high performance concrete in bridge decks, approach slabs, and other structural elements as follow:
The placement temperature should be maintained between 50 F and 80 F (10 C and 26.7 C).
The maximum internal temperature should not exceed 140 F (60 C). The minimum surface temperature is 45 F (7.2 C). The maximum temperature differential should not exceed 35 F (19.4 C). Maturity meter probes need to be installed to monitor concrete temperatures
according to AASHTO T 325.
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Internal cooling, external heating, or insulation needs to be provided to ensure the temperature differential does not exceed 35 F (19.4 C) during placing, curing, cooling, form stripping, and after curing ends.
Flatwork needs to be cured for at least 14 days and structural elements for at least 10 days.
The maximum temperature in prestressed concrete should not exceed 160 F (71.1 C).
For structural concrete, the maximum percent of total cementitious material by mass should be limited to 25% for fly ash or other pozzolans (AASHTO M 295), 50% for slag (AASHTO M 302), and 50% for fly ash and slag together. The maximum water-tocementitious material ratio of 0.54 is used for concrete Class S (Seal).
U.S. State DOTs Mass Concrete Specifications The authors have reviewed available state DOT specifications to gain a comprehensive understanding of mass concrete temperature and other requirements. A reasonable effort was made to locate and identify specifications on each state DOT website. Only 23 states appeared to have mass concrete specifications or mass concrete special provisions publicly available. Table 8 lists these states, Table 9 presents available document types, and Figure 34 shows a map of US states which have mass concrete specifications or provisions publicly available. Mississippi and New Hampshire provide maximum temperature limits only for normal concrete placements in their specifications. A summary of the mass concrete requirements is organized under eleven subtitles:
1. Mass concrete definition 2. Maximum temperature and temperature differential limits
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3. Maximum placement temperature 4. Maximum and minimum total SCM content 5. Percentage of SCM replacement allowed 6. Compressive strength and/or HoH requirements 7. Water to cementitious material ratio and slump requirements 8. Curing requirements 9. Formwork removal time 10. Methods to cool down concrete temperature 11. Temperature monitoring requirements Table 10 through Table 21 summarize these requirements. Figure 34 through Figure 40 provide visual representations of selected items on maps. For these figures, a US map template was obtained from yourfreetemplates.com and modified to present the differences in state DOT mass concrete requirements.
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Table 8 State DOTs that publish mass concrete specifications.

Publish

Do Not Publish (or are not found)

Alabama

Alaska Arizona

Arkansas, 2014

Colorado

California, 2015

Connecticut

Delaware, 2017

Connecticut

Florida, 2017 Georgia, 2013

District of Colombia Hawaii

Idaho, 2017

Indiana

Illinois, 2016

Kansas

Iowa, 2015 Kentucky, 2012

Maine Maryland

Louisiana, 2018

Michigan

Massachusetts, 2015

Missouri

Minnesota, 2018

Montana

Mississippi, 2017*

Nebraska

New Hampshire, 2016*

Nevada

New Jersey, 2016

New Mexico

New York, 2019

North Dakota

North Carolina, 2018 Ohio, 2016

Oklahoma Oregon

Rhode Island, 2016 South Carolina, 2007

Pennsylvania South Dakota

Texas, 2014

Tennessee

Virginia, 2016

Utah

West Virginia, 2010

Vermont

Washington

Wisconsin

Wyoming

Note: * indicates state published concrete specifications in which mass concrete requirements are provided.

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Table 9 Mass concrete document type by state DOT.

DOTs

Type of Mass Concrete Specification

Arkansas Standard Specifications for Highway Construction (ArDOT, 2014)

California Delaware Florida Georgia

Standard Specifications (Caltrans, 2015)
Standard Specifications for Road and Bridge Construction (DelDOT, 2016) Standard Specifications for Road and Bridge Construction (FDOT, 2017)
Special Provision (GDOT, 2013)

Idaho Illinois Iowa

Standard Specifications for Highway construction (IDT, 2017) Standard Specifications for Road and Bridge Construction (IDOT, 2016) Standard Specifications (Iowa DOT, 2015)

Kentucky Louisiana

Standard Specifications for Road and Bridge Construction (KYTC, 2012)
Standard Specifications for Roads and Bridges (DOTD, 2016)

Massachusetts Supplemental Specifications (MassDOT, 2015)

Minnesota Mississippi

Standard Specifications for Construction (MnDOT, 2018)
Standard Specifications for Road and Bridge Construction (MDOT, 2017)

New Hampshire New Jersey New York

General Provisions (NHDOT, 2016) Standard Specifications for Road and Bridge Construction (NJDOT, 2007) Standard Specifications (NYSDOT, 2019)

North Carolina Standard Specifications for Roads and Structures (NCDOT, 2018)

Ohio

Construction and Material Specifications (ODOT, 2016)

Rhode Island Special Provisions (RIDOT, 2016)

South Carolina Texas Virginia

Standard Specifications for Highway Construction (SCDOT, 2007) Standard Specifications for construction and Maintenance of Highways, Streets, and Bridges (TxDOT, 2014) Road and Bridge Specifications (VDOT, 2016)

West Virginia Standard Specifications for Roads and Bridges (WVDOT, 2010)

79

Figure 34 US states with mass concrete specifications publicly available. 80

Table 10 Mass concrete definition by state DOT.

DOTs

Mass Concrete Definition

California

Minimum dimension exceeding 7 feet shall be constructed as mass concrete. Any large volume of cast-in-place concrete with dimensions large enough to require that measures be taken to cope with generation of heat and attendant volume change to minimize cracking.

Delaware Designers are responsible to identify.

Florida Georgia

Concrete with a minimum dimension exceeding 3 feet and the ratio of volume of concrete to the surface area greater than 1 foot.
All drilled shafts with design diameters greater than 6 feet.
Any large volume of cast-in-place concrete with dimensions large enough to require measures be taken to cope with the generation of heat and attendant volume change to minimize cracking.
Any substructure concrete element whose least dimension is greater than 5 feet (excluding drilled shafts).

Idaho

Placements thicker than 4 feet.

Illinois Iowa Kentucky Louisiana
Massachusetts

Concrete structures when the least dimension for a drilled shaft, foundation, footing, substructure, or superstructure concrete pour exceeds 5 feet (1.5 m).
Any concrete footing with a least dimension greater than 5 feet. Other concrete placements with a least dimension greater than 4 feet.
Any concrete placement, excluding drilled shafts, with a least plan dimension of 6 feet or greater.
Structural concrete placement with a least dimension of 4 feet or greater, or if designated on the plans or in the project specifications as mass concrete.
Cement concrete placements where all volumetric dimensions of the placement are 4 feet (1.2 m) or greater.
Cement concrete placements of other dimensions where measures must be taken to mitigate potential cracking caused by heat of hydration when such placements are specifically designated as mass cement concrete on the plans.

Minnesota Least dimension of 4 feet.

North Carolina

Substructure components (footings, columns, or caps) when the smallest dimension of that component is between 6 feet and 8 feet.

Ohio

Components with a minimum dimension of 5 feet (1.5 m) or greater. Drilled shafts with a dimension of 7 feet (2.1 m) diameter or greater.

Rhode Island

Any element with the ratio of the total volume to the surface area equal to or exceeding 0.6 and a minimum dimension of 3 feet in any of the 3 planes.

South Carolina

Pour that has dimensions of 5 feet or greater in 3 different directions. For circular cross-sections, a pour with a diameter of 6 feet or greater and a length of 5 feet or greater. Mass concrete requirements do n