Iowa Mass Concrete for Bridge Foundations Study

Iowa Mass Concrete for Bridge Foundations Study
Iowa Mass Concrete for
Bridge Foundations Study –
Phase II
Final Report
February 2014
Sponsored by
Iowa Department of Transportation
Federal Highway Administration
(InTrans Project 10-384)
About the Institute for Transportation
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Technical Report Documentation Page
1. Report No.
InTrans Project 10-384
2. Government Accession No.
4. Title and Subtitle
Iowa Mass Concrete for Bridge Foundations Study – Phase II
3. Recipient’s Catalog No.
5. Report Date
February 2014
6. Performing Organization Code
InTrans Project 10-384
8. Performing Organization Report No.
7. Author(s)
Jacob J. Shaw, Charles T. Jahren, Kejin Wang, and Jinxin “Linda” Li
9. Performing Organization Name and Address
10. Work Unit No. (TRAIS)
Institute for Transportation
Iowa State University
11. Contract or Grant No.
2711 South Loop Drive, Suite 4700
Ames, IA 50010-8664
12. Sponsoring Organization Name and Address
13. Type of Report and Period Covered
Iowa Department of Transportation, 800 Lincoln Way, Ames, IA 50010
Phase II Final Report
14. Sponsoring Agency Code
Federal Highway Administration, U.S. Department of Transportation, 1200 New
SPR RB09-011
Jersey Avenue SE, Washington, DC 20590
15. Supplementary Notes
Visit www.intrans.iastate.edu for color pdfs of this and other research reports.
16. Abstract
The early-age thermal development of structural mass concrete elements has a significant impact on the future durability and longevity
of the elements. If the heat of hydration is not controlled, the elements may be susceptible to thermal cracking and damage from delayed
ettringite formation.
In the Phase I study, the research team reviewed published literature and current specifications on mass concrete. In addition, the team
observed construction and reviewed thermal data from the westbound (WB) I-80 Missouri River Bridge. Finally, the researchers
conducted an initial investigation of the thermal analysis software programs ConcreteWorks and 4C-Temp&Stress.
The Phase II study is aimed at developing guidelines for the design and construction of mass concrete placements associated with large
bridge foundations. This phase included an additional review of published literature and a more in-depth investigation of current mass
concrete specifications. In addition, the mass concrete construction of two bridges, the WB I-80 Missouri River Bridge and the US 34
Missouri River Bridge, was documented.
An investigation was conducted of the theory and application of 4C-Temp&Stress. ConcreteWorks and 4C-Temp&Stress were
calibrated with thermal data recorded for the WB I-80 Missouri River Bridge and the US 34 Missouri River Bridge. ConcreteWorks and
4C-Temp&Stress were further verified by means of a sensitivity study.
Finally, conclusions and recommendations were developed, as included in this report.
17. Key Words
bridge foundations—concrete thermal damage—mass concrete construction—
thermal stress analysis—specifications
19. Security Classification (of this
20. Security Classification (of this
report)
page)
Unclassified.
Unclassified.
Form DOT F 1700.7 (8-72)
18. Distribution Statement
No restrictions.
21. No. of Pages
22. Price
161
NA
Reproduction of completed page authorized
IOWA MASS CONCRETE FOR BRIDGE
FOUNDATIONS STUDY – PHASE II
Final Report
February 2014
Principal Investigator
Charles T. Jahren
Professor
Institute for Transportation, Iowa State University
Co-Principal Investigator
Kejin Wang
Professor
Institute for Transportation, Iowa State University
Research Assistants
Jacob J. Shaw
Jinxin “Linda” Li
Authors
Jacob J. Shaw, Charles T. Jahren, Kejin Wang, and Jinxin “Linda” Li
Sponsored by
the Iowa Department of Transportation and
the Federal Highway Administration
State Planning and Research Funding
(SPR RB09-011)
Preparation of this report was financed in part
through funds provided by the Iowa Department of Transportation
through its Research Management Agreement with the
Institute for Transportation
(InTrans Project 10-384)
A report from
Institute for Transportation
Iowa State University
2711 South Loop Drive, Suite 4700
Ames, IA 50010-8664
Phone: 515-294-8103
Fax: 515-294-0467
www.intrans.iastate.edu
TABLE OF CONTENTS
ACKNOWLEDGMENTS ........................................................................................................... xiii
EXECUTIVE SUMMARY ...........................................................................................................xv
CHAPTER 1. INTRODUCTION ....................................................................................................1
1.1 OBJECTIVES ............................................................................................................................1
1.2 IOWA DOT MASS CONCRETE SPECIFICATION ...............................................................1
1.3 LITERATURE REVIEW ..........................................................................................................2
1.3.1 Restraint and Thermal Stress ......................................................................................2
1.3.1.1 Internal Restraint ..........................................................................................2
1.3.1.2 External Restraint.........................................................................................3
CHAPTER 2. SPECIFICATION SURVEY ....................................................................................5
2.1 OVERVIEW ..............................................................................................................................5
2.2 INTRODUCTION .....................................................................................................................5
2.3 METHODOLOGY ....................................................................................................................5
2.4 RESULTS ..................................................................................................................................6
2.4.1 Mass Concrete Definition ...........................................................................................7
2.4.2 Temperature Restrictions ............................................................................................8
2.4.3 Mix Proportion Requirements.....................................................................................9
2.4.4 Construction ..............................................................................................................11
2.4.5 Thermal Control Verification ...................................................................................11
2.5 DISCUSSION ..........................................................................................................................14
CHAPTER 3. CASE STUDIES .....................................................................................................15
3.1 INTRODUCTION ...................................................................................................................15
3.2 WESTBOUND I-80 MISSOURI RIVER BRIDGE OVERVIEW .........................................15
3.3 US 34 MISSOURI RIVER BRIDGE OVERVIEW ................................................................15
3.4 CONSTRUCTION ...................................................................................................................16
3.4.1 Footing Subbase and Support ...................................................................................16
3.4.2 Formwork Material ...................................................................................................18
3.4.3 Pier Elements ............................................................................................................20
3.4.4 Concrete Placement ..................................................................................................21
3.4.5 Consolidation ............................................................................................................23
3.4.6 Insulation...................................................................................................................24
3.4.7 Cooling Pipes ............................................................................................................29
3.4.8 Thermal Monitoring ..................................................................................................34
3.4.9 Formwork Removal ..................................................................................................37
3.5 CONCRETE MIX PROPORTION..........................................................................................37
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3.6 ENVIRONMENTAL CONDITIONS .....................................................................................38
CHAPTER 4. 4C-TEMP&STRESS ..............................................................................................39
4.1 OVERVIEW ............................................................................................................................39
CHAPTER 5. SOFTWARE CALIBRATION ...............................................................................42
5.1 OVERVIEW ............................................................................................................................42
5.2 WESTBOUND I-80 MISSOURI RIVER BRIDGE ................................................................42
5.2.1 ConcreteWorks .........................................................................................................42
5.2.1.1 Inputs Overview .........................................................................................42
5.2.1.2 Concrete Mix Proportion Inputs ................................................................43
Mixture Proportion Inputs............................................................43
Material Property Inputs ..............................................................44
Mechanical Property Inputs .........................................................45
5.2.1.3 Construction Parameter Inputs ...................................................................46
General Inputs ..............................................................................47
Shape Inputs .................................................................................47
Dimension Inputs .........................................................................48
Construction Inputs ......................................................................49
5.2.1.4 Environmental Condition Inputs ................................................................50
5.2.1.5 Sensor Location Corrections ......................................................................50
5.2.1.6 Results ........................................................................................................51
5.2.1.7 Discussion ..................................................................................................53
5.2.2 4C-Temp&Stress.......................................................................................................54
5.2.2.1 Inputs..........................................................................................................54
5.2.2.2 Results and Discussion ..............................................................................55
5.3 US 34 MISSOURI RIVER BRIDGE ......................................................................................61
5.3.1 ConcreteWorks .........................................................................................................61
5.3.1.1 Inputs Overview .........................................................................................61
5.3.1.2 Concrete Mix Proportion Inputs ................................................................61
5.3.1.3 Construction Parameter Inputs ...................................................................61
General Inputs ..............................................................................61
Shape Inputs .................................................................................62
Dimension Inputs .........................................................................62
Construction Inputs ......................................................................63
5.3.1.4 Environmental Conditions Inputs ..............................................................64
5.3.1.5 Sensor Location Corrections ......................................................................65
5.3.1.6 Results ........................................................................................................65
5.3.1.7 Discussion ..................................................................................................66
5.3.2 4C-Temp&Stress.......................................................................................................67
5.3.2.1 Inputs..........................................................................................................67
5.3.2.2 Results ........................................................................................................68
CHAPTER 6. SENSITIVITY STUDY..........................................................................................70
6.1 OVERVIEW ............................................................................................................................70
vi
6.2 CONCRETEWORKS SENSITIVITY STUDY ......................................................................70
6.2.1 Overview ...................................................................................................................70
6.2.2 Baseline Inputs ..........................................................................................................71
6.2.3 Results .......................................................................................................................73
6.2.3.1 Dimensional Size .......................................................................................73
6.2.3.2 Fresh Placement Temperature....................................................................75
6.2.3.3 Curing Method ...........................................................................................76
6.2.3.4 Forming Method ........................................................................................77
6.2.3.5 Formwork Removal Time ..........................................................................78
6.2.3.6 Subbase Material ........................................................................................80
6.2.3.7 Sensor Location .........................................................................................82
6.2.3.8 Ambient Air Temperature ..........................................................................87
6.2.3.9 Cement Content .........................................................................................89
6.2.3.10 Fly Ash Substitution ................................................................................90
6.2.3.11 GGBFS Substitution ................................................................................92
6.2.3.12 Combined Class F Fly Ash and GGBFS Substitution .............................94
6.2.4 Discussion .................................................................................................................97
6.3 4C-TEMP&STRESS SENSITIVITY STUDY RESULTS .....................................................97
6.4 DISCUSSION ON SENSITIVITY STUDIES ......................................................................100
CHAPTER 7. TEMPERATURE DIFFERENCE CASE STUDIES ...........................................101
7.1 I-80 Bridge .................................................................................................................101
7.2 US 34 Bridge..............................................................................................................103
CHAPTER 8. CONCLUSIONS AND RECOMMENDATIONS ...............................................105
REFERENCES ............................................................................................................................107
APPENDIX A. INSTALLATION AND LAYOUT OF THERMAL SENSORS .......................109
APPENDIX B. COMPARISON BETWEEN 4C (PREDICTION) AND CTL (ACTUAL).......115
APPENDIX C. CONCRETEWORKS WESTBOUND I-80 CASE STUDY THERMAL
RESULTS ........................................................................................................................127
APPENDIX D. US 34 CASE STUDY THERMAL RESULTS .................................................138
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LIST OF FIGURES
Figure 1.1. Internal restraint mechanism due to thermal gradients (Kim 2010) ..............................3
Figure 1.2. External restraint mechanism due to thermal gradients (Kim 2010) .............................4
Figure 3.1. Clay subbase with steel bearing pile ...........................................................................17
Figure 3.2. Crushed rock subbase with steel bearing pile..............................................................18
Figure 3.3. US 34 Missouri River Bridge Pier 3 footing ...............................................................19
Figure 3.4. WB I-80 Missouri River Bridge column formwork ....................................................19
Figure 3.5. US 34 Missouri River Bridge column formwork ........................................................20
Figure 3.6. Typical bridge pier element sections ...........................................................................21
Figure 3.7. US 34 Bridge Pier 4 footing concrete placement ........................................................22
Figure 3.8. US 34 Bridge Pier 2 footing concrete placement ........................................................23
Figure 3.9. Jensen Construction Company flexible shaft vibratory compactor .............................24
Figure 3.10. Insulation attached to wood-formed footings ............................................................25
Figure 3.11. WB I-80 Bridge wood-formed footing shoring .........................................................26
Figure 3.12. Shored formwork insulating blanket .........................................................................27
Figure 3.13. Elevated placement with insulating blankets wrapped around the catwalks .............28
Figure 3.14. Steel formed footing with insulating blanket ............................................................28
Figure 3.15. US 34 Bridge cooling pipe system water supply pump ............................................29
Figure 3.16. Cooling pipe system supply line manifold ................................................................30
Figure 3.17. WB I-80 Bridge cooling pipe system manifold .........................................................30
Figure 3.18. US 34 Bridge cooling pipe system manifold .............................................................31
Figure 3.19. PEX cooling pipes being installed on a WB I-80 bridge footing (Iowa DOT) .........32
Figure 3.20. Installed PVC piping on US 34 Bridge footing .........................................................33
Figure 3.21. Distance between formwork and outermost rebar/thermal sensor location – large
distance ..............................................................................................................................35
Figure 3.22. Distance between formwork and outermost rebar/thermal sensor location ..............36
Figure 3.23. Typical rebar cover for mass concrete footing ..........................................................36
Figure 5.1. ConcreteWorks thermal analysis discrete temperature point layout ...........................51
Figure 5.2. Comparison between the measured and 4C predicted temperatures (Pier 1 footing
of WB I-80 Bridge) ............................................................................................................56
Figure 5.3. Line of equality plot for 780 data points of maximum temperature results from
measured temperatures and 4C predicted temperatures.....................................................57
Figure 5.4. Temperature discrepancy plot for various structural elements ....................................58
Figure 5.5. Sample temperature development iso-curve results for right-third cross section of Pier
3 footing with cooling pipe applied at 48 hours (not to scale)...........................................59
Figure 5.6. Sample tensile stress/strength iso-curve results for lower right corner of cross
section of Pier 3 footing with cooling pipe applied at 12 hours (not to scale) ..................60
Figure 5.7. Sample tensile stress/strength iso-curve results for lower right corner of cross section
of Pier 3 footing with cooling pipe applied at 168 hours (not to scale) .............................60
Figure 5.8. Pier 4 footing temperature results for US 34 Bridge ...................................................68
Figure 5.9. Pier 4 footing σt/ft ratio results for US 34 Bridge .......................................................69
Figure 6.1. ConcreteWorks maximum temperature development and average ambient air
temperature with time ........................................................................................................80
Figure 6.2. Placement temperature versus subbase material thermal conductivity .......................82
Figure 6.3. Pier 3 footing contour plot at time of maximum temperature difference ....................83
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Figure 6.4. Top, side, and center sensor error locations ................................................................84
Figure 6.5. Temperature errors for sensor placement errors ..........................................................85
Figure 6.6. ConcreteWorks ambient air temperature and maximum temperature with time
after placement ...................................................................................................................88
Figure 6.7. Maximum temperature and maximum temperature difference sensitivity study
results for 0% and 50% GGBFS substitution ....................................................................93
Figure 6.8. Combined class F fly ash and GGBFS substitution maximum temperature results....97
Figure 7.1. Relationship between бt/ft ratio and the maximum temperature difference ..............102
Figure 7.2. Case study results for Pier 4 footing of US 34 Bridge ..............................................104
Figure A.1. Installation of thermal sensors with cable ties and tie wire ......................................109
Figure A.2. Top surface and center sensors installed with electrical tape ...................................110
Figure A.3. Thermal sensor supported and protected with supplemental rebar ..........................111
Figure A.4. Typical top surface and center sensor layout ............................................................112
Figure A.5. Typical side surface and center sensor layout ..........................................................113
Figure A.6. Verification of proper sensor function after installation ..........................................114
Figure B.1. Maximum temperature development for Pier 2 footing comparison between
measured (CTL) and predicted (4C) ................................................................................115
Figure B.2. Maximum temperature development for Pier 3 footing comparison between
measured (CTL) and predicted (4C) ................................................................................115
Figure B.3. Maximum temperature development for Pier 4 footing comparison between
measured (CTL) and predicted (4C) ................................................................................116
Figure B.4. Maximum temperature development for Pier 5 footing comparison between
measured (CTL) and predicted (4C) ................................................................................116
Figure B.5. Maximum temperature development for Pier 6 footing comparison between
measured (CTL) and predicted (4C) ................................................................................117
Figure B.6. Maximum temperature development for Pier 1 stem comparison between
measured (CTL) and predicted (4C) ................................................................................117
Figure B.7. Maximum temperature development for Pier 2 stem comparison between
measured (CTL) and predicted (4C) ................................................................................118
Figure B.8. Maximum temperature development for Pier 3 stem comparison between
measured (CTL) and predicted (4C) ................................................................................118
Figure B.9. Maximum temperature development for Pier 4 stem comparison between
measured (CTL) and predicted (4C) ................................................................................119
Figure B.10. Maximum temperature development for Pier 5 stem comparison between
measured (CTL) and predicted (4C) ................................................................................119
Figure B.11. Maximum temperature development for Pier 7 stem comparison between
measured (CTL) and predicted (4C) ................................................................................120
Figure B.12. Maximum temperature development for Pier 9 stem comparison between
measured (CTL) and predicted (4C) ................................................................................120
Figure B.13. Maximum temperature development for Pier 1 cap comparison between
measured (CTL) and predicted (4C) ................................................................................121
Figure B.14. Maximum temperature development for Pier 2 cap comparison between
measured (CTL) and predicted (4C) ................................................................................121
Figure B.15. Maximum temperature development for Pier 3 cap comparison between
measured (CTL) and predicted (4C) ................................................................................122
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Figure B.16. Maximum temperature development for Pier 4 cap comparison between
measured (CTL) and predicted (4C) ................................................................................122
Figure B.17. Maximum temperature development for Pier 5 cap comparison between
measured (CTL) and predicted (4C) ................................................................................123
Figure B.18. Maximum temperature development for Pier 1 column comparison between
measured (CTL) and predicted (4C) ................................................................................123
Figure B.19. Maximum temperature development for Pier 2 column comparison between
measured (CTL) and predicted (4C) ................................................................................124
Figure B.20. Maximum temperature development for Pier 3 column comparison between
measured (CTL) and predicted (4C) ................................................................................124
Figure B.21. Maximum temperature development for Pier 4 column comparison between
measured (CTL) and predicted (4C) ................................................................................125
Figure B.22. Maximum temperature development for Pier 2 column comparison between
measured (CTL) and predicted (4C) ................................................................................125
Figure B.23. Maximum temperature development for Pier 7 column comparison between
measured (CTL) and predicted (4C) ................................................................................126
Figure B.24. Maximum temperature development for Pier 10 column comparison between
measured (CTL) and predicted (4C) ................................................................................126
Figure C.1. WB I-80 case study thermal results – Pier 1 footing ................................................127
Figure C.2. WB I-80 case study thermal results – Pier 1 stem/column .......................................127
Figure C.3. WB I-80 case study thermal results – Pier 1 cap ......................................................128
Figure C.4. WB I-80 case study thermal results – Pier 2 footing ................................................128
Figure C.5. WB I-80 case study thermal results – Pier 2 stem ....................................................129
Figure C.6. WB I-80 case study thermal results – Pier 2 column ................................................129
Figure C.7. WB I-80 case study thermal results – Pier 2 cap ......................................................130
Figure C.8. WB I-80 case study thermal results – Pier 3 footing ................................................130
Figure C.9. WB I-80 case study thermal results – Pier 3 stem ....................................................131
Figure C.10. WB I-80 case study thermal results – Pier 3 column ..............................................131
Figure C.11. WB I-80 case study thermal results – Pier 3 cap ....................................................132
Figure C.12. WB I-80 case study thermal results – Pier 4 footing ..............................................132
Figure C.13. WB I-80 case study thermal results – Pier 4 stem ..................................................133
Figure C.14. WB I-80 case study thermal results – Pier 4 column ..............................................133
Figure C.15. WB I-80 case study thermal results – Pier 4 cap ....................................................134
Figure C.16. WB I-80 case study thermal results – Pier 5 footing ..............................................134
Figure C.17. WB I-80 case study thermal results – Pier 5 stem ..................................................135
Figure C.18. WB I-80 case study thermal results – Pier 5 column ..............................................135
Figure C.19. WB I-80 case study thermal results – Pier 5 cap ....................................................136
Figure C.20. WB I-80 case study thermal results – Pier 6 footing ..............................................136
Figure C.21. WB I-80 case study thermal results – Pier 6 column ..............................................137
Figure D.1. US 34 case study thermal results – Pier 2 footing – A .............................................138
Figure D.2. US 34 case study thermal results – Pier 2 footing – B .............................................138
Figure D.3. US 34 case study thermal results – Pier 2 footing – C .............................................139
Figure D.4. US 34 case study thermal results – Pier 2 footing – D .............................................139
Figure D.5. US 34 case study thermal results – Pier 2 column – A.............................................140
Figure D.6. US 34 case study thermal results – Pier 2 column – B .............................................140
Figure D.7. US 34 case study thermal results – Pier 2 column – C .............................................141
x
Figure D.8. US 34 case study thermal results – Pier 2 column – D.............................................141
Figure D.9. US 34 case study thermal results – Pier 2 cap ..........................................................142
Figure D.10. US 34 case study thermal results – Pier 3 footing – C ...........................................142
Figure D.11. US 34 case study thermal results – Pier 3 footing – D ...........................................143
Figure D.12. US 34 case study thermal results – Pier 3 column – A...........................................143
Figure D.13. US 34 case study thermal results – Pier 3 column – B ...........................................144
Figure D.14. US 34 case study thermal results – Pier 3 column – C ...........................................144
Figure D.15. US 34 case study thermal results – Pier 3 column – D...........................................145
LIST OF TABLES
Table 1.1. Iowa DOT maximum allowable temperature difference limits ......................................2
Table 2.1. Agencies with and without identified mass concrete specifications...............................6
Table 2.2. State agency specification reference ...............................................................................7
Table 2.3. Mass concrete definition by agency................................................................................8
Table 2.4. Temperature restrictions by agency ................................................................................9
Table 2.5. Cement and compressive strength restriction by agency ..............................................10
Table 2.6. Supplementary cementitious material substitution by agency ......................................10
Table 2.7. Fresh placement temperature by agency .......................................................................11
Table 2.8. Sensor locations and cover by agency ..........................................................................12
Table 2.9. Thermal control completion time by agency ................................................................13
Table 5.1. Summary of 4C inputs and how to obtain them ...........................................................40
Table 5.2. Models used for prediction of concrete properties in 4C program ...............................40
Table 5.3. Comparison of 4C outputs with ConcreteWorks ..........................................................41
Table 5.4. Ready Mixed Concrete Co. mix design for WB I-80 Missouri River Bridge ..............43
Table 5.5. Mixture proportion inputs for WB I-80 Missouri River Bridge ...................................44
Table 5.6. Ash Grove Cement Company type I/II cement Bogue calculated values (Ash
Grove Cement Company 2010) .........................................................................................44
Table 5.7. Material property inputs for the WB I-80 Missouri River Bridge ................................45
Table 5.8. Calculated Nurse-Saul constants for each placement for the WB I-80 Missouri
River Bridge .......................................................................................................................46
Table 5.9. Placement date and time for each element of the WB I-80 Missouri River Bridge .....47
Table 5.10. Dimensions of elements for the WB I-80 Missouri River Bridge ..............................48
Table 5.11. Construction inputs for the WB I-80 Missouri River Bridge .....................................50
Table 5.12. WB I-80 case study thermal results - footings ............................................................52
Table 5.13. WB I-80 case study thermal results - stems ................................................................52
Table 5.14. WB I-80 case study thermal results - columns ...........................................................52
Table 5.15. WB I-80 case study thermal results - caps ..................................................................53
Table 5.16. Maximum temperature error statistical analysis of the WB I-80 Missouri River
case study ...........................................................................................................................53
Table 5.17. Maximum temperature difference error statistical analysis of the WB I-80 Missouri
River case study .................................................................................................................53
Table 5.18. Concrete properties and material properties inputs used in I-80 Bridge case study ...55
Table 5.19. Placement date and time for each element of the US 34 Missouri River Bridge .......62
Table 5.20. Dimensions of elements for the US 34 Missouri River Bridge ..................................63
xi
Table 5.21. Construction inputs for the US 34 Missouri River Bridge .........................................64
Table 5.22. US 34 case study thermal results - footings ................................................................65
Table 5.23. US 34 case study thermal results - columns ...............................................................66
Table 5.24. US 34 case study thermal results - cap .......................................................................66
Table 5.25. Maximum temperature error statistical analysis of US 34 Missouri River case
study ...................................................................................................................................66
Table 5.26. Maximum temperature difference error statistical analysis of US 34 Missouri
River case study .................................................................................................................67
Table 5.27. 4C-Temp&Stress Inputs .............................................................................................67
Table 6.1. Sensitivity parameter list and classification..................................................................70
Table 6.2. Sensitivity study baseline inputs ...................................................................................72
Table 6.3. Ash Grove type I/II Bogue calculated values ...............................................................73
Table 6.4. Actual maximum and minimum temperature for 10/30/08-11/13/08 ...........................73
Table 6.5. Dimensional size parameter ranges ..............................................................................74
Table 6.6. Dimensional size sensitivity study results ....................................................................75
Table 6.7. Fresh placement temperature sensitivity study results .................................................76
Table 6.8. Curing method sensitivity study results ........................................................................77
Table 6.9. Forming method sensitivity study results .....................................................................78
Table 6.10. Formwork removal time sensitivity study results .......................................................79
Table 6.11. Subbase material sensitivity study results ..................................................................81
Table 6.12. Subbase material thermal properties (Riding 2007) ...................................................81
Table 6.13. Top surface sensor temperature error by depth placement error ................................86
Table 6.14. Ambient air temperature sensitivity study maximum and minimum temperature
inputs ..................................................................................................................................87
Table 6.15. Ambient air temperature sensitivity study results.......................................................88
Table 6.16. Cement content sensitivity study inputs .....................................................................89
Table 6.17. Cement content sensitivity study results .....................................................................90
Table 6.18. Class F fly ash sensitivity study inputs .......................................................................90
Table 6.19. Class C fly ash sensitivity study inputs ......................................................................91
Table 6.20. Class F fly ash sensitivity study results ......................................................................91
Table 6.21. Class C fly ash sensitivity study results ......................................................................91
Table 6.22. GGBFS substitution sensitivity study inputs ..............................................................92
Table 6.23. GGBFS substitution sensitivity study results .............................................................93
Table 6.24. Combined class F fly ash and GGBFS substitution – cement content (lb/cy)
inputs ..................................................................................................................................94
Table 6.25. Combined class F fly ash and GGBFS substitution – class F fly ash (lb/cy)
inputs ..................................................................................................................................95
Table 6.26. Combined class F fly ash and GGBFS substitution – GGBFS (lb/cy) inputs ............95
Table 6.27. Combined class F fly ash and GGBFS substitution results – maximum
temperature (°F) .................................................................................................................96
Table 6.28. Combined class F fly ash and GGBFS substitution results – maximum
temperature difference (°F) ................................................................................................96
Table 6.29. Parameters, ranges, and results considered in sensitivity study .................................99
xii
ACKNOWLEDGMENTS
The research team would like to acknowledge the Iowa Department of Transportation (DOT) for
sponsoring this research and the Federal Highway Administration for state planning and research
(SPR) funds used for this project.
The research team would like to thank our technical advisory committee (TAC) including James
Nelson, Wayne Sunday, Todd Hanson, Ahmad Abu-Hawash, Chris Cromwell, Mark Dunn, Curt
Monk, and Linda Narigon. We would also like to thank Scott Nixon, Steve Maifield, Jeremy
Purvis, and Jason Cole of the Iowa DOT.
The research team would also like John Gajda and Jon Feld for their cooperation with our
research. Finally, the research team wishes to thank Landon Streit, Dan Timmons, Ryan
Cheeseman, and Steve Hague for their assistance with our research.
xiii
EXECUTIVE SUMMARY
The early-age thermal development of structural mass concrete elements has a significant impact
on the future durability and longevity of the elements. If the heat of hydration is not controlled,
the elements may be susceptible to thermal cracking and damage from delayed ettringite
formation.
In the Phase I study, the research team reviewed published literature and current specifications
on mass concrete. The team also observed construction and reviewed thermal data from the
westbound (WB) I-80 Missouri River Bridge. In addition, the researchers conducted an initial
investigation of the thermal analysis software programs ConcreteWorks and 4-CTemp&Stress.
The present study is aimed at developing guidelines for the design and construction of mass
concrete placements associated with large bridge foundations. This phase consisted of the
following research activities:





Update literature review and preliminary thermal stress analysis
Observe mass concrete construction practices
Review construction observations and data from the WB I-80 Missouri River Bridge and US
34 Missouri River Bridge
Model thermal activity in ConcreteWorks and 4C-Temp&Stress
Develop recommendations
This report describes the activities conducted and results obtained from the Phase II study.
The Phase II study included an additional review of published literature and a more in-depth
investigation of current mass concrete specifications. In addition, the mass concrete construction
of two bridges, the WB I-80 Missouri River Bridge and the US 34 Missouri River Bridge, was
documented.
An investigation was conducted regarding the theory and application of 4C-Temp&Stress.
ConcreteWorks and 4C-Temp&Stress were calibrated by using thermal data recorded for the WB
I-80 Missouri River Bridge and the US 34 Missouri River Bridge. ConcreteWorks and 4CTemp&Stress were further verified by means of a sensitivity study.
Finally, conclusions and recommendations were developed as included in this report.
xv
CHAPTER 1. INTRODUCTION
Mass concrete is a structural element of concrete with dimensions large enough to require actions
to prevent excessive heat development. Heat development in a concrete element is the result of
hydration of the cement. If the heat development is not controlled, the element may experience
thermal cracking or delayed ettringite formation.
Thermal cracking is the result of large thermal gradients in a massive placement. Thermal
gradients induce stress in the placement, which results from the exterior portion of the placement
dissipating heat more rapidly than the interior portion. If the induced stress exceeds the tensile
strength of the recently placed concrete, the placement is likely to experience thermal cracking.
Historically, keeping the maximum temperature differential below 35°F was found to reduce the
likelihood of thermal cracking.
Delayed ettringite formation, also known as heat-induced delayed expansion (HIDE), results
from excessively high temperatures in a concrete placement. High temperatures in a placement
decompose the ettringite that had been previously formed in the concrete and suppresses further
ettringite formation.
In the future, if moisture is present in the concrete, ettringite may begin to form in the now solid
cement paste, causing expansive pressure in the concrete. If the expansive pressures become too
extreme, the placement may experience cracking. It has been established that preventing the
maximum temperature in the placement from reaching 160°F will reduce the probability of
HIDE.
1.1 Objectives
The objectives of this research are to provide insight on the early-age thermal development of
mass concrete, provide recommendations for the Iowa Department of Transportation (DOT)
mass concrete specification, and present best practices for mass concrete construction. The
research utilized the software packages ConcreteWorks and 4C-Temp&Stress to model the
thermal development of mass concrete elements.
1.2 Iowa DOT Mass Concrete Specification
The Iowa DOT currently has a developmental specification for mass concrete (Control Heat of
Hydration DS-09047, August 17, 2010). The specification was based on national industry
practices and experiences on the westbound (WB) I-80 bridge over the Missouri River (between
Council Bluffs, Iowa and Omaha, Nebraska). The goal of the specification is to provide concrete
structures free of thermal damage resulting from heat of hydration during the curing of large
concrete cross-sections.
To mitigate the effects of heat of hydration, the Iowa DOT specification has implemented
thermal limits for mass concrete placements. To prevent delayed ettringite formation, the
1
specification states that the maximum temperature in a placement may not exceed 160°F during
the time of heat dissipation. To prevent thermal cracking, the specification has laid out maximum
temperature differentials for placements as shown in Table 1.1.
Table 1.1. Iowa DOT maximum allowable temperature difference limits
Time after
Placement
(hrs)
0-24
24-48
48-72
>72
Maximum
Temperature
Difference (°F)
20
30
40
50
1.3 Literature Review
Historically, there have been many methods used to control the heat of hydration of mass
concrete placements and reduce the thermal damage. Approaches that put limits on mix
proportions and material properties include using a low-cement content, reduced heat cements
and/or increased aggregate size; increasing coarse aggregate, fly ash, and/or ground granulated blast
furnace slag (GGBFS) content; and requiring water-reducing admixtures.
Construction practices used to reduce thermal damage include reducing the fresh placement
temperature, post-cooling the concrete with internal cooling pipes, pouring placements during cooler
times (nighttime or cooler times of the year), water curing, reducing placement lift height, and using
steel forms for rapid heat dissipation or wood forms and insulation for reduced heat dissipation
(Kosmatka et al. 2002).
1.3.1 Restraint and Thermal Stress
Cracking in mass concrete is the result of restraint, which induces tensile stresses that exceed the
relatively low tensile strength of the concrete. All mass concrete is restrained both internally by
the element itself, and externally by the support system of the element.
1.3.1.1 Internal Restraint
When mass concrete is placed, the core of the concrete experiences large temperature increases
due to the heat of hydration and the inability of concrete to efficiently transfer heat to the
surrounding environment. The increase in temperature causes the core of the concrete to expand
due to thermal expansion. Due to the proximity to the surrounding environment, the surface of
the concrete cools more rapidly compared to the core, causing the surface of the placement to
contract relative to the core, due to thermal expansion. The respective volume changes in the
concrete causes compressive forces to develop in the core and tension forces to develop at the
surface as shown by Figure 1.1.
2
Figure 1.1. Internal restraint mechanism due to thermal gradients (Kim 2010)
If the tensile stress in the concrete exceeds the developed tensile strength of the concrete, the
concrete will experience thermal cracking.
1.3.1.2 External Restraint
External restraint is the result of the mass concrete support structure. After the concrete has
reached its peak temperature, the placement begins to cool and, subsequently, contracts in
volume. The contraction of the concrete is resisted by external restraints, such as the subbase,
rigid support structure, or adjoining structure supporting the mass concrete element. Figure 1.2
shows how the volumetric changes of mass concrete are resisted by external restraint.
3
Figure 1.2. External restraint mechanism due to thermal gradients (Kim 2010)
The contracting volume of concrete will develop tensile stresses resulting from the resistance
provided by the external restraint. If the tensile stresses exceed the developed tensile strength of
the concrete, the placement will experience cracking.
4
CHAPTER 2. SPECIFICATION SURVEY
2.1 Overview
The chapter describes the mass concrete specification survey for state and federal agencies in the
US. The following three sections describe the methodology utilized to identify the specifications,
the results of the identified specifications, and a discussion of the results.
2.2 Introduction
Mass concrete specification requirements throughout the US vary greatly between agencies. The
goal of the specification survey was to identify current trends in mass concrete requirements in
the US. Aspects of the mass concrete specification that were surveyed included the definition of
mass concrete, concrete mix portion requirements, thermal control requirements, construction
requirements, design requirements, and additional special requirements.
The next section of this chapter describes the methodology that was used to complete the
specification survey. The section after that describes the results of the survey. The final section
of provides a discussion of the sensitivity survey results.
2.3 Methodology
The specification survey was completed by investigating the mass concrete specification of the
51 state highway agencies, including the District of Columbia (DC) and two federal agencies.
The first stage of the survey involved searching the internet for current standard specifications
and additional special provisions of the state agencies in an effort to identify specifications
independently. Following the initial internet search, state highway agencies that did not appear to
have a mass concrete specification were contacted by telephone in a further effort to determine if
the agency has a supplemental or developmental mass concrete specification that was not posted
on the internet.
If an agency is listed as not having an identified specification, it does not mean the agency does
not have a specification, rather that a specification was not identified in the search process. If a
specification was not identified, it means the agency either did not respond, was unable to
identify the specification, or did not have a specification. Furthermore, agencies with minimal
mass concrete specifications were excluded from the survey for lack of scope. As an example of
lack of scope, the standard specification identifies only that mass concrete shall use type II
cement.
5
2.4 Results
Thirteen different mass concrete specifications were identified including standard specifications,
special provisions, special notes, developmental specifications, and structural design guidelines,
as shown in Table 2.1. As listed on the right side of the table, the researchers were unable to
identify a mass concrete specification for 40 agencies.
Table 2.1. Agencies with and without identified mass concrete specifications
Agencies with Specification
Arkansas DOT
California DOT
Florida DOT
Idaho DOT
Illinois DOT
Iowa DOT
Kentucky DOT
New Jersey DOT
New York DOT
Rhode Island DOT
South Carolina DOT
Texas DOT
West Virginia DOT
Agencies without Specification
FHWA
Missouri DOT
NAVFAC
Montana DOT
Alabama DOT
Nebraska DOR
Alaska DOT
Nevada DOT
Arizona DOT
New Hampshire DOT
Colorado DOT
New Mexico DOT
Connecticut DOT
North Carolina DOT
Delaware DOT
North Dakota DOT
District of Columbia DOT Ohio DOT
Georgia DOT
Oklahoma DOT
Hawaii DOT
Oregon DOT
Indiana DOT
Pennsylvania DOT
South Dakota DOT
Kansas DOT
Tennessee DOT
Louisiana DOT
Maine DOT
Utah DOT
Maryland DOT
Vermont DOT
Massachusetts DOT
Virginia DOT
Michigan DOT
Washington DOT
Minnesota DOT
Wisconsin DOT
Mississippi DOT
Wyoming DOT
The type, reference, and year for the identified specifications are listed in Table 2.2.
6
Table 2.2. State agency specification reference
Agency
Arkansas DOT
California DOT
Florida DOT
Idaho DOT
Illinois DOT
Iowa DOT
Kentucky DOT
Specification Type
Standard specification
Standard specification
Standard specification
Structural design guidelines
Standard specification
Special provision
Developmental specification
Special note
New Jersey DOT
New York DOT
Rhode Island DOT
South Carolina DOT
Texas DOT
West Virginia DOT
Standard specification
Special provision
Standard specification
Standard specification
Standard specification
Special provision
Reference
AHTD 2003
California DOT 2010
Florida DOT 2010
Florida DOT 2006
Idaho DOT 2004
Illinois DOT 2012
Iowa DOT 2010
Kentucky Transportation
Cabinet 2008
New Jersey DOT 2007
New York State DOT 2012
Rhode Island 2010
South Carolina DOT 2007
Texas DOT 2004
West Virginia DOT 2006
2.4.1 Mass Concrete Definition
The definition of mass concrete designates which concrete elements must be designed and
constructed in accordance with the specified mass concrete requirements. The definition of mass
concrete often varies with the element type, dependent on if the placement is a drilled shaft,
footing, substructure, or superstructure.
The definition of mass concrete is usually related to the dimensional size of the placement.
Generally, mass concrete is defined by the least dimension of the concrete pour, or the smallest
dimension in all directions of the placement. In addition, mass concrete may be defined by the
volume of placement, surface area of the placement, or ratio of the dimensions. If an agency
wishes to have additional control over which placements are deemed mass concrete, elements
may be designated on a case-by-case basis.
Table 2.3 indicates the definition of mass concrete provided by the specifications identified in
the survey. The definitions vary greatly between agencies, with the lesser dimensions varying
from 3 to 5 ft. In addition, the definition of mass concrete pertains to varying element types from
only footings to all concrete placements. A common trend of the specifications is to define mass
concrete differently for cast-in-place concrete piers, piles, or shafts. Similarly, five specifications
identify mass concrete by designating it on the plans, allowing the agency to define mass
concrete on a case-by-case basis depending on the situation.
7
Table 2.3. Mass concrete definition by agency
Agency
Arkansas DOT
California DOT
Florida DOT
Idaho DOT
Illinois DOT
Iowa DOT
Kentucky DOT
New Jersey DOT
New York DOT
Rhode Island
DOT
South Carolina
DOT
Texas DOT
West Virginia
DOT
NA- not available
Definition
NA
Cast in place concrete piles with a diameter greater than 8 ft;
other definitions are reserved
Concrete with a least dimension of 3 ft and the volume to surface
area of the concrete exceeds one 1 ft; drilled shafts with a
diameter greater than 6 ft
Footings thicker than 4 ft
Least dimension of 5 ft for drilled shafts, foundations, footings,
substructures, or superstructures
Least dimension of footings greater than 5 ft, or other concrete
placements with a least dimension of 4 ft, excluding drilled shafts
Least plan dimension 5 ft or greater, excluding drilled shafts
As defined on the plans
NA
Concrete dimensions in 3 directions is 5 ft or more
Concrete has dimensions of 5 ft or greater in three directions; for
circular sections, a diameter of 6 ft or greater and a length of 5 ft
or greater, excluding driller shafts and foundation seals
Least dimension of 5 ft or greater, or as designated on the plans
Least dimension of 4 ft for footings, pier shafts, arms, and caps,
excluding drilled caissons and tremie seals
2.4.2 Temperature Restrictions
Specifications typically provide temperature restrictions to control thermal damage from delayed
ettringite formation and thermal gradients. The temperature restrictions provided by agencies
with an identified mass concrete specification are shown in Table 2.4.
8
Table 2.4. Temperature restrictions by agency
Agency
Arkansas DOT
California DOT
Maximum
Temperature
(°F)
NA
160
Florida DOT
Idaho DOT
Illinois DOT
Iowa DOT
180
NA
150
160
Kentucky DOT
New Jersey DOT
New York DOT
Rhode Island DOT
South Carolina DOT
Texas DOT
West Virginia DOT
NA - not available
160
160
NA
NA
160
160
160
Maximum Temperature
Difference (°F)
36
To be determined to prevent
cracking due to heat of hydration
35
35
35, up to 50 if approved
20 (0-24 hrs) 30 (24-48 hrs)
40 (48-72 hrs) 50 (>72 hrs)
35
35
35
70
35
35
35
Maximum temperature restrictions are specified to prevent delayed ettringite formation in the
concrete. Of the agencies with an identified mass concrete specification, the maximum allowable
temperature in the placement ranges from 150 to 180°F.
Maximum temperature differentials are specified to control the thermal damage to internal
restraint. The majority of the specifications identified limited the maximum temperature
difference to 35°F. The California DOT (CalTrans) standard specification takes a performancebased approach allowing the contractor to submit maximum temperature differentials that
prevent “cracking due to heat of hydration.”
The Iowa DOT developmental specification for mass concrete uses a gradient approach to define
the maximum temperature differential. Over the first four days after the completion of the pour,
the maximum temperature difference is allowed to increase 10°F for each day after placement,
ranging from 20 to 50°F. The gradient approach allows the contractor to take advantage of the
increase in concrete strength over time.
2.4.3 Mix Proportion Requirements
Specifications may limit the mix proportion of the concrete to control the strength, durability,
and heat generation from the hydration of the concrete. Table 2.5 and Table 2.6 show the
specification requirements for allowable cement types, cement content, compressive strength,
and supplementary cementitious material substitution for agencies identified as having a
specification.
9
Table 2.5. Cement and compressive strength restriction by agency
Agency
Arkansas DOT
California DOT
Florida DOT
Idaho DOT
Illinois DOT
Allowable
Cement
Types
II or I if
approved
NA
NA
NA
NA
Iowa DOT
I/II, IP, or IS
Kentucky DOT
New Jersey DOT
New York DOT
NA
NA
Type II
cement only
NA
NA
NA
NA
Rhode Island DOT
South Carolina DOT
Texas DOT
West Virginia DOT
NA - not available
Cement Content
NA
NA
NA
NA
Minimum Portland cement
content of 330lb/cy
Minimum cement content
of 560 lb/cy
NA
NA
Total cementitious content
of 300kg/m3 (506 lb/cy)
NA
NA
NA
NA
Compressive
Strength
3500psi-90 day,
3000psi-28 day
NA
NA
NA
NA
NA
NA
NA
21MPa(3046 psi)56 day
NA
NA
NA
NA
Table 2.6. Supplementary cementitious material substitution by agency
Agency
Arkansas DOT
California DOT
Florida DOT
Idaho DOT
Illinois DOT
Iowa DOT
Kentucky DOT
New Jersey DOT
New York DOT
Rhode Island DOT
South Carolina DOT
Texas DOT
West Virginia DOT
Supplementary Cementitious Material Substitution
70
NA
Fly ash substitution of cement by weight 18-50%, slag
substitution 50%-70%
NA
Maximum cement substitution for fly ash 40%, GGBFS 65%
Total cement substitution of 50% for fly ash and slag, class C
fly ash limited to 20%
Substitution of GGBFS up to 50% of cement content, total
fly ash and slag substitution of 50%, with a maximum fly ash
substitution of 20%
NA
Class F fly ash 20-50% substitution of cementitious materials
NA
NA
NA
Total slag and fly ash substitution of 50%, maximum fly ash
substitution of 25%, and maximum slag substitution of 50%
NA - not available
10
The specification survey shows that many agencies do not have mix proportion restrictions
specifically for mass concrete. In addition, there is little commonality between agencies in regard
to mix proportion requirements.
2.4.4 Construction
Specification requirement for the construction of mass concrete placements are difficult to
establish because of the wide range of element types, locations, and thermal concerns.
Construction practices that may be reasonable for an element with a large risk of thermal damage
may not be reasonable for a simple placement with little concern of thermal damage. Therefore,
only the fresh placement temperature of a placement is restricted typically for the construction of
mass concrete elements.
Table 2.7 shows the restrictions on fresh placement temperature for mass concrete construction.
The results show that many agencies do not place additional restrictions on the fresh placement
temperature for mass concrete. In addition, there is little commonality in fresh placement
temperature restrictions between agencies. The range of maximum fresh placement temperature
is 60 to 90°F for agencies with identified specifications.
Table 2.7. Fresh placement temperature by agency
Agency
Arkansas DOT
California DOT
Florida DOT
Idaho DOT
Illinois DOT
Iowa DOT
Kentucky DOT
New Jersey DOT
New York DOT
Rhode Island DOT
South Carolina DOT
Texas DOT
West Virginia DOT
NA - not available
Fresh Placement
Temperature Range (°F)
Maximum temperature 75
NA
NA
NA
40-90
40-70
Maximum temperature 60
NA
NA
NA
Maximum temperature 80
50-75
NA
2.4.5 Thermal Control Verification
Thermal control verification is the process of verifying that the thermal control requirements of
the placement are met. Generally, mass concrete placements are monitored during construction
to ensure that temperature restrictions are not violated, or in danger of being violated. Pours are
monitored with temperature sensors installed in locations that provide the maximum and
11
minimum temperatures of the placement. These temperatures provide the maximum temperature
and maximum temperature difference to verify the thermal requirements.
Proper sensor location is crucial to gauge the thermal stresses in the placement accurately. If
sensors are not installed properly, the temperature reading may have significant error, providing
misleading results. In addition, the surface sensors may compromise the durability and cosmetic
appearance of the concrete if installed too close to the surface. To capture accurate results,
sensors must be installed in the proper location in the placement. Table 2.8 shows the sensor
location requirements and the surface cover requirements for sensors placed near the surface.
Table 2.8. Sensor locations and cover by agency
Agency
Arkansas DOT
California DOT
Florida DOT
Idaho DOT
Illinois DOT
Iowa DOT
Kentucky DOT
Sensor Locations
Contractor developed, agency approved
Calculated hottest location, 2 outer faces, 2 corners, top
surface
Contractor developed, agency approved
NA
Contractor developed, agency approved. In addition, the
ambient air temperature and entrance/exit of cooling
water
Center of the placement, midpoint of side closest to the
center, midpoint of top surface, corner of the placement
furthest from the center, and ambient air temperature
2 at separate locations near the geometric center, 2 at the
center of the exterior face with the longest distance from
the interior sensors, and that has the least sun exposer
New Jersey DOT
As close as possible to the center, and at the exposed
surface
New York DOT
Center of the placement, base of the mass, the surface of
the mass, center of the exterior face that is the shortest
distance from the center of the mass
Rhode Island DOT
Designated by the engineer
South Carolina DOT Contractor developed, agency approved
Texas DOT
NA
West Virginia DOT Hottest location, on at least two outer faces, two corners,
and top surfaces
NA - not available
Surface
Sensor
Cover
NA
NA
NA
NA
1-3 in.
2 in.
minimum
1"
NA
NA
NA
NA
NA
NA
The survey shows that many agencies do not directly specify the sensor location or the required
cover for surface sensors. In addition, there is little uniformity in the sensor location or surface
sensor concrete cover requirements among agencies that have identified specification
requirements.
12
Thermal control completion time denotes the time when the contractor ceases the monitoring of
the concrete and thermal protective procedures. At completion, the threat of thermal damage
without outside intervention has been reduced to an acceptable level. Table 2.9 shows the
thermal control completion time by agency.
Table 2.9. Thermal control completion time by agency
Agency
Arkansas DOT
California DOT
Florida DOT
Idaho DOT
Illinois DOT
Iowa DOT
Kentucky DOT
New Jersey DOT
New York DOT
Rhode Island DOT
South Carolina
DOT
Texas DOT
West Virginia
DOT
Time of Thermal Completion
At least 7 days
Maximum internal temperature is falling, difference between core
temperature and ambient temperature is within the ambient air
temperature for 3 consecutive days, and no adjacent mass
concrete element to be poured
The maximum temperature differential begins to decrease, and
the core temperature is within 35°F of the ambient air temperature
7 days
After the maximum temperature is reached, post-cooling is no
longer required, and the maximum temperature differential does
not exceed 35°F
Maximum temperature difference is within 50°F of the average
ambient temperature of the previous seven days
Temperature at the center is within 35°F of the average ambient
air temperature of the past 7 days
15 days, or until the interior concrete temperature is within 35°F
of the lowest ambient temperature
Maximum temperature differential is reached and begins to
decrease
NA
2 weeks, or until the interior concrete temperature is within 35°F
of the lowest ambient temperature
4 days
Maximum temperature differential is reached and decreasing, and
the maximum temperature is within the maximum allowable
temperature differential of the ambient air temperature
NA - not available
The survey shows that the majority of specifications require that the maximum temperature in
the placement to be within the maximum temperature differential requirement of the ambient air
temperature. This requirement allows the formwork and insulation to be removed from the
placement without increasing the risk of thermal damage. In addition, this requirement will
typically force the placement to reach a maximum temperature and to begin to cool.
13
2.5 Discussion
The results show that there are very large differences between mass concrete specifications for
each agency. There is little consensus between agencies on what aspect of mass concrete mix
proportion, construction, and thermal control need to be specified. Aspects that are specified by
all agencies still generally have large discrepancies in requirements.
14
CHAPTER 3. CASE STUDIES
3.1 Introduction
The purpose of this chapter is to provide a description of conditions under which the westbound
(WB) I-80 Missouri River Bridge and the US 34 Missouri River Bridge were constructed and
verify that they are typical examples of midwestern border bridges. The first two sections of this
chapter provide a general overview of the WB I-80 and US 34 bridges. The following sections
describe the conditions under which the bridges were constructed, the mix proportion used, and
the environmental conditions.
3.2 Westbound I-80 Missouri River Bridge Overview
The WB I-80 Missouri River Bridge is a 2,477 ft 10 in. by 84 ft continuous welded girder bridge.
The bridge spans the Missouri River connecting Council Bluffs, Iowa to Omaha, Nebraska. The
bridge consisted of 27 different mass concrete elements as defined by the Iowa DOT mass
concrete developmental specification (DS-09047).
The mass concrete elements were constructed from August 2008 through August 2009. Elements
defined as mass concrete included footings, stems, columns, and pier caps. The elements had a
range of sizes varying from a least dimension of 4 ft to 10.5 ft.
The construction of the mass concrete elements was completed by two separate contractors,
Jensen Construction Company of Des Moines, Iowa and Cramer & Association, Inc. of Grimes,
Iowa. CTL Group of Skokie, Illinois was engaged by Jensen Construction Company to be the
consultant for the construction of the mass concrete elements.
3.3 US 34 Missouri River Bridge Overview
The US 34 Missouri River Bridge is a 3,276 ft 1 in. by 86 ft 3 in. continuous welded girder
bridge with pretensioned, prestressed concrete beam approaches. The bridge crosses the Missouri
River south of Omaha, Nebraska and Council Bluffs, Iowa. The bridge began construction in
2010 and is scheduled for completion in 2014.
The bridge has several mass concrete elements as defined by the Iowa DOT mass concrete
developmental specification (DS-09047). The elements include footings, columns, and caps that
were constructed with and without cooling pipes. The elements have least dimensions ranging in
size from 5.5 ft to 6.5 ft.
The construction of the mass concrete elements was completed by Jensen Construction
Company. The CTL Group was engaged by Jensen Construction Company to be the consultant
for the construction of the mass concrete elements.
15
3.4 Construction
This section describes the general conditions in which the mass concrete elements on the WB
I-80 Bridge and US 34Bridge were constructed. The exact conditions that the elements were
constructed under are described in more depth in Chapter 6.
3.4.1 Footing Subbase and Support
Each footing has a supporting mechanism that transfers the load placed on the footing to the soil
structure below. In addition to supporting the footing, the support structure also retains the
footings externally. To support the footings on the WB I-80 Bridge, two techniques were used:
steel bearing piles and drilled shafts. Piers 1 through 5, 7, 10, and 11utilized HP 12 x 84 steel
bearing piles to support the respective footings. The Pier 6 footing was supported by 48 in.
diameter drilled shafts, and Piers 7 and 8 were supported by 72 in. diameter drilled shafts.
Similarly, on the US 34 Bridge, Piers 1 through 4 and 7 through 17 were supported by HP 14 x
89 steel bearing piles. Piers 5 and 6 were supported by 30 individual 48 in. diameter open-ended
steel piling.
The subbase material that each footing is poured against depends on the location of the footing.
Footings that are placed in or close to the river require a seal coat, which is a layer of concrete
that is several feet thick, be cast below the footing to prevent water from seeping through the
foundation soils into the area where the footing will be cast. Each footing that is placed on a seal
coat is still restrained by the footing support structure, piling or drilled shafts, that extends
through the seal coat, in addition to the seal coat.
Footings that were not cast on seal coats were typically placed on clay subbase, a typical soil
condition along rivers in the Midwest. Alternatively, a layer of gravel was also placed on top of
the clay subbase to provide a firm and dry casting surface in some instances. The WB I-80
Bridge footings were cast against a clay subbase, while the US 34 Bridge footings were cast
against a crushed rock subbase, as shown by Figure 3.1 and Figure 3.2, respectively.
16
Figure 3.1. Clay subbase with steel bearing pile
17
Figure 3.2. Crushed rock subbase with steel bearing pile
3.4.2 Formwork Material
Two different formwork materials, wood and steel, were used to form the placements on both the
WB I-80 and US 34 Bridge. The choice of formwork material is dependent on the type of
placement that is being formed. Generally, the placements that are shorter in height and are
relatively simple shapes used wood formwork. The typical applications of the wooden formwork
include simple footings, and the patching of steel formwork gaps, such as the bottom of pier
caps. Steel formwork is used typically on larger placements that develop more hydraulic
pressure, such as columns, stems, large footings, and large caps.
The wood formwork consists of three-quarter-inch plywood attached to two-by-four- and twoby-six-inch supporting members with nails. A typical example of the wood formwork used on
both projects is shown by Figure 3.3. The steel formwork that was used on both projects
consisted of yellow EFCO formwork. Figure 3.4 and Figure 3.5 show typical examples of the
steel formwork used on both projects.
18
Figure 3.3. US 34 Missouri River Bridge Pier 3 footing
Figure 3.4. WB I-80 Missouri River Bridge column formwork
19
Figure 3.5. US 34 Missouri River Bridge column formwork
3.4.3 Pier Elements
To ease in the construction of the bridges, construction joints were installed in the piers at
discrete locations. For both the WB I-80 and US 34 Bridges, the piers were typically poured in
four sections, footing, stem, column, and cap, as shown by Figure 3.6. The allowable locations
for the construction joints were designated by the bridge designer.
20
Cap
Stems
Column
Footing
Figure 3.6. Typical bridge pier element sections
For small or simple elements, the number of pier elements was reduced for both bridges. The
stem and column on Pier 1 from the WB I-80 were combined into one pour due to the relatively
small size of the stem and column. The US 34 Bridge utilized four separate footings and columns
for Piers 1 through 3 and 8 through 17, which simplified the geometry and reduced the size of
each element. As a result, the piers were poured in three sections: footing, column, and cap.
3.4.4 Concrete Placement
The relative size of the concrete placements on the WB I-80 and US 34 Bridges required large
amounts of concrete to be placed in a single unit. To complete the pours, two different methods
were utilized: concrete hopper buckets and concrete pump trucks. Many factors that affect the
placement method include the size of the placement, congestion of the pour site, height of the
pour, and availability of equipment.
Concrete pump trucks allow the concrete to be placed at a lower height compared to hopper
buckets in congested areas, as shown by Figure 3.7, especially when equipped with an extended
tremie pipe.
21
Figure 3.7. US 34 Bridge Pier 4 footing concrete placement
Concrete hopper buckets were also utilized on placements with large depths by utilizing tremie
pipes to reduce the drop height.
A lower concrete placement height reduces the risk of segregation for the concrete. The use of
concrete hopper buckets is often a less expensive alternative to concrete pump trucks for
accessible placements with little congestions. Concrete hopper buckets are typically less
expensive for contractors, as they do not require renting additional equipment. Due to the size of
concrete hopper buckets, the concrete is dropped generally above the top of the formwork. If a
tremie pipe is not utilized, the application of concrete hopper buckets is limited to placements of
relatively short depth to prevent concrete segregation. Figure 3.8 shows the use of a concrete
hopper bucket to pour a 5.5 ft deep foundation.
22
Figure 3.8. US 34 Bridge Pier 2 footing concrete placement
3.4.5 Consolidation
Consolidation of concrete is an essential step in the placement of mass concrete. If concrete is
not consolidated properly, the concrete element will have substantial voids reducing the overall
strength and durability of the element. The need for concrete consolidation on both the WB I-80
and US 34 bridges required the utilization of concrete vibrators with flexible shafts to vibrate the
concrete internally. To assure that the concrete was consolidated adequately, the concrete was
vibrated at each individual concrete placement layer. A typical example of the vibratory
compactor used on both bridges is shown in Figure 3.9.
23
Figure 3.9. Jensen Construction Company flexible shaft vibratory compactor
3.4.6 Insulation
To control the maximum temperature difference of the mass concrete placements, all elements
on the WB I-80 and US 34 Bridges were insulated. The typical insulating method on both
bridges was to wrap the exterior of the formwork and the top of the placements with a black
insulating blanket with a specified R value rating of 5.
The general practices for each placement was to use a single layer of insulating blankets on each
surface of the placement, except for the bottom of the footings. Insulation was also used to cover
any exposed steel (generally rebar) protruding from the placement. As steel is an efficient heattransferring material, it is necessary to keep the rebar at relatively the same temperature as the
concrete to prevent large thermal gradients from developing near the rebar.
In an attempt to control the thermal development of the placements efficiently, blankets were
added and removed from the placement over the duration of the period of thermal control.
During the construction of the WB I-80 Bridge, conditions arose that required adding insulating
blankets to the placement to prevent exceeding the maximum temperature difference limits. In
some instances, additional insulating blankets were added to all sides, but were limited typically
to the top surface. During the construction of the WB I-80 Bridge, instances also arose that
allowed for the unexpected early removal of insulating blankets. If the placement was not in
danger of exceeding the specified maximum temperature difference limits, insulation blankets
24
were removed occasionally to dissipate the heat generated in the placement more rapidly.
Removal of some or all of the insulating blankets reduced the time in which the placement was
under thermal control, allowing shorter formwork cycle times. The removal of insulating
blankets was also utilized if the placement was in danger of exceeding the allowable maximum
temperature of the placement.
The typical condition of the insulating blankets used on both bridges was that of used insulating
blankets. Generally, the blankets had minor damage from previous use including many holes
from being attached to previous formwork. In addition, many blankets had small rips and tears.
To attach the insulation to wooden formwork, the insulation was nailed typically around the
edges to secure the blanket in place. The blankets were attached to formwork to the degree
required to withstand the weather conditions, but not to a degree that greatly prevented the
movement of air between the formwork and the insulating blankets. The blankets typically
appeared to be sufficiently lapped at the joints between blankets so that one could assume the
concrete unit was covered by a continuous layer. Figure 3.10 shows a typical situation with an
insulating blanket attached to wood formwork.
Figure 3.10. Insulation attached to wood-formed footings
25
The insulation blankets were attached to the exterior of the formwork generally before the
placement of the concrete began. The top surface of the placement was covered with insulation
blankets once the concrete had taken a set. The top surface was viewed as the most sensitive
surface, as there was no formwork to provide additional thermal resistance and, therefore, extra
care was taken to assure that the blankets were lapped properly on the top surfaces.
As a result of the formwork shoring on certain footing of the WB I-80 Bridge, the sides of the
footings were unable to be attached to the formwork directly. To provide additional rigidity to
formwork, shores were installed to support the formwork walls by the cofferdam sheet pile walls
as shown in Figure 3.11. As a result, the insulating blankets were unable to be attached directly
to the formwork.
Figure 3.11. WB I-80 Bridge wood-formed footing shoring
In an effort to provide thermal insulation for the sides of the placement, thermal blankets were
applied on top of the shoring, bridging the gap between the top of the formwork and the
cofferdam walls, as shown in Figure 3.12. The insulating blankets were intended to prevent
airflow along the sides of the footing and to capture the heat of the placement in the void. The
effectiveness of the insulating blanket installed on top of the shoring is unknown.
26
Figure 3.12. Shored formwork insulating blanket
Elevated placements on both bridges occasionally utilized catwalks to aid in the assembly of the
formwork. As the catwalks are connected to exterior surfaces of the formwork, it is difficult to
attach the insulation blankets directly to the formwork. To provide insulation to the placement,
the blankets were wrapped around the catwalks, capturing a layer of air in between the insulation
blankets and the formwork, as shown in Figure 3.13.
27
Figure 3.13. Elevated placement with insulating blankets wrapped around the catwalks
Placements that were formed with steel were insulated similarly to that of wood formwork. The
main difference is that steel formwork on both bridges required the insulation blankets be tied to
the formwork. The insulating blankets were tied with reinforcing tie-wire onto the formwork
struts. A typical example of insulating blankets attached to steel formwork for both bridges is
shown in Figure 3.14.
Figure 3.14. Steel formed footing with insulating blanket
28
3.4.7 Cooling Pipes
Cooling pipes were utilized on both bridges to control the thermal development of placements
with relatively large dimensions. Cooling pipes were also used occasionally to minimize the time
in which the placement was required to remain under thermal control to reduce the formwork
cycle time.
The water required for the cooling pipe systems for both bridges was supplied by the adjacent
Missouri River or contactor-dug wells. The water was pumped to the placement and through the
cooling pipes by means of diesel, gas, or electric powered water pumps. The water pump
configuration utilized on the US 34 Bridge is shown in Figure 3.15.
Figure 3.15. US 34 Bridge cooling pipe system water supply pump
To reach the required placements, the water had to be pumped over long distances in some
instances. The large distances required the use of a large water pump that could overcome the
head loss developed by both the elevation differential between the river and the placement, as
well as the pipe friction. In the case of the US 34 Bridge, the water had to be pumped more than
400 ft horizontally and more than 50 ft vertically to supply the cooling pipe system for the Pier 4
cap.
The water was pumped through piping, approximately 4 to 8 in. diameter, from the water pump,
until the piping reached the placement. As the water approaches the placement, the piping splits
at a manifold to allow for the use of multiple cooling pipe systems, which also allows the
following piping to be of reduced size to increase the pressure, as shown by Figure 3.16.
29
To cooling
pipe system
Supply from water pump
Manifold
Figure 3.16. Cooling pipe system supply line manifold
As the piping reaches the placement, the water is pumped through an additional manifold.
Typical examples of the manifolds used on the WB I-80 and US 34 Bridges are shown in Figure
3.17 and Figure 3.18, respectively. The manifold allows each separate loop of the cooling pipe
system to be supplied by the single supply line. The manifold also allows the contractor to adjust
the flow rate of water through each loop of the system.
Figure 3.17. WB I-80 Bridge cooling pipe system manifold
30
Figure 3.18. US 34 Bridge cooling pipe system manifold
Each cooling pipe system consisted of several loops that pumped the water through the
placement. Each loop was spaced typically in both the vertical and horizontal directions by two
to three feet. In addition, the material utilized to construct the loops inside the placement varied
between the two projects. The WB I-80 Bridge utilized 3/4 inch PEX (cross-linked polyethylene)
piping as shown in Figure 3.19 as well as 3/4 inch PVC (polyvinyl chloride) piping. The US 34
Bridge utilized 1 inch PVC piping as shown in Figure 3.20. The PEX piping on the WB I-80
Bridge was attached to the rebar with cable ties, and the PVC piping on the US 34 Bridge was
attached to the rebar with tie wire and cable ties.
31
Figure 3.19. PEX cooling pipes being installed on a WB I-80 bridge footing (Iowa DOT)
32
Figure 3.20. Installed PVC piping on US 34 Bridge footing
Once the water was pumped through the circulation loop in the placement, the water was
pumped out of the placement to different locations. Depending on the element, the water leaving
the placement was either pumped directly back to the river or drained into the cofferdam. The
water that was drained into the cofferdam would be pumped out subsequently by the cofferdam
dewatering pumps.
Given that the cooling pipes utilized an open system, the systems were not pressure tested. To
verify that there were no leaks in the cooling pipe system, water was run through the entire
system before concrete placement began, and the system was checked for leaks.
To avoid shocking the placement thermally with the cooling pipes, the circulation of water began
immediately after the completion of the pour. In addition, once the circulation of the water
through the placement was stopped, the circulation of the water was never restarted. Therefore,
the circulation of water was continued generally until the threat of thermal damage to the
placement was completely past.
The temperature of the water circulating through the placement was measured as the water
entered and exited the placement. The temperature of the water pumped from the adjacent river
was approximately equal to that of the average ambient air temperature at the time the placement
was poured. The temperature of the water supplied by contractor-dug wells was approximately
15°F lower than the average air temperature in the summer.
33
The difference in the water temperature between the entrance and exit locations was typically 1
to 3°F. The flow rate through each loop was adjusted, by means of the manifold, to maintain an
acceptable temperature difference of the water entering and exiting the placement. The
contactors estimated the flow rate through each loop to be approximately 10 gal/minute.
Following the completion of the thermal control requirements, the cooling pipes were cut off at
the surface of the placement and pumped full of high-strength grout.
3.4.8 Thermal Monitoring
In accordance with the Iowa DOT mass concrete developmental specification, each placement on
both bridges defined as mass concrete was monitored through the use of thermal sensors. To
monitor the thermal development of the placements, two different thermal sensor models were
utilized. The WB I-80 Bridge utilized both intelliRock Temperature Loggers and iButton model
DS 1921 thermal sensors. The US 34 Bridge utilized only the intelliRock Temperature Loggers.
The location of the thermal sensors varied between both the project and the element type. During
the construction of the WB I-80 Bridge, each placement, including all footings, stems, columns,
and caps, utilized three discrete sensor locations to monitor the thermal development of the
elements. The location of the sensors included the side surface, top surface, and center of the
placement. The location of the sensors are defined as follows: side surface – the center of the
surface of the side closest to the geometric center of the placement, top surface – the center of
the top (unformed) surface of the placement, and center – the geometric center of the placement.
In addition to the primary sensors, each location utilized a redundant thermal sensor in case the
primary sensors failed.
Similarly to the WB I-80 Bridge, the US 34 Bridge utilized three discrete sensor locations on
many of the elements. However, some elements utilized only two sensor locations, resulting
from the geometry of the placement. Given the threat of thermal cracking is the result of large
temperature change over relatively short distances, it was determined to be unnecessary to
monitor the thermal development at surfaces that were relatively long distances from the
geometric center of the placement. Therefore, the columns and other elements with extreme
dimension proportions utilized only two sensors. In addition, all placements utilized thermal
sensors to monitor the current ambient conditions. Placements that utilized cooling pipes also
monitored the temperature of the water entering and exiting the placement.
The Iowa DOT development specification for mass concrete requires that the minimum concrete
cover for each sensor to be two inches; however, the specification does not state a maximum
amount of concrete cover (Iowa DOT 2010). As a result of the specification, the concrete cover
for surface sensors varied greatly from element to element.
In general practice, the sensor measuring the surface temperature of the placement was located
on the interior side of the rebar nearest the surface. The sensor was placed on the interior of the
rebar in an effort to prevent damage to the sensor during concrete placement. Due to the
34
structural rebar layout for each placement and fabrication errors in the rebar construction and
placement, the distance from the sensor and the surface varied greatly, as shown by Figure 3.21
and Figure 3.22. In addition, it was commonly observed that additional concrete was cast above
the required height on many footings, in some cases exceeding 6 inches, greatly affecting the
sensor concrete cover.
Figure 3.23 shows the rebar concrete cover for a footing, with the red chalk line representing the
finish pour height.
Figure 3.21. Distance between formwork and outermost rebar/thermal sensor location –
large distance
35
Figure 3.22. Distance between formwork and outermost rebar/thermal sensor location
Figure 3.23. Typical rebar cover for mass concrete footing
36
To determine the location of each sensor, typically, no measuring devices were used. Generally,
the sensors were placed approximately at their intended locations, which may provide noticeable
errors in the thermal monitoring.
Three different methods were used to attach the thermal sensors and their respective wires to the
rebar cage: tie wire, cable ties, and electrical tape. Care was taken in the installation of the
sensors and wires to prevent damage during concrete placement including supporting the wires
and sensors with additional rebar, attaching the sensors and wires to the underside of the rebar,
and avoiding slack in the wires. The images show the installation of the thermal sensors and the
typical layout of installed thermal sensors.
Each wire was marked before installation to allow the thermal readings to be assigned to the
respective sensor locations. It was common practice to test each thermal sensor after installation,
prior to the placement of the concrete, to identify sensors that may have been damaged.
The thermal data were recorded in one-hour intervals. In addition, the data were monitored
remotely, by checking the thermal readings visually, to assure that the placement was not in
threat of thermal damage during the duration of the thermal control period. Upon the completion
of the thermal control period, the data were submitted to the Iowa DOT as part of the required
field reports.
3.4.9 Formwork Removal
To prevent thermal damage to the placement, formwork was retained on the placement typically
until the time of thermal control expired. The Iowa DOT mass concrete development
specification requires that the thermal control of each placement must be maintained until the
interior temperature of the placement is within 50°F of the average ambient air temperature.
Formwork was commonly left on the placement beyond the time required by the thermal control
requirements until it was required for use on another placement. It was viewed as an
inconvenience to store the formwork on the jobsite rather than leave it on the placement until
required.
The range of formwork removal times, as recorded by the contractors, ranged from 91 to 347
hours for both the WB I-80 Bridge and the US 34 Bridge. The large variance is the result of
different thermal control requirements due to the varying complexity levels of each placement, as
well as varying formwork cycle rates.
3.5 Concrete Mix Proportion
Both bridges utilized the same mix proportion. The concrete mix proportion along with the
material and mechanical properties are described in detail in Chapter 5.
37
3.6 Environmental Conditions
Between the mass construction of the WB I-80 Bridge and the US 34 Bridge, the full range of
environmental conditions in the Omaha, Nebraska area was experienced. The environmental
conditions under which each element was placed are described in detail in Chapter 7.
38
CHAPTER 4. 4C-TEMP&STRESS
4.1 Overview
4C-Temp&Stress (4C) is a computer program developed by the Danish Technological Institute
that provides the abilities to outline concrete geometry, carry out full or approximated
calculations, and view the results in a graphical interface. The program can perform thermal
analysis and stress analysis of mass concrete development.
Assumptions are used in 4C to simplify the FE analyses. For example, the ambient temperature
is an assumed sinusoidal curve varying from a single maximum and minimum temperature value
for the entire duration of the analysis, while actual weather conditions differ from day to day.
The maximum temperature sensor is assumed to be located at the center of concrete, and the
minimum temperature sensor is assumed to be placed at 3 in. from the top surface of concrete.
Furthermore, specific heat, thermal conductivity, and coefficient of thermal expansion can be
assumed using obtained literature values to simplify the analysis. Other assumptions, such as
mesh size, analysis period, and calculation parameters, can be found in the 4C user manual
(1998).
Table 5.1 describes the required inputs of 4C.
Table 5.2 further indicates prediction models that can be used to obtain those inputs. The models
were established based on literature findings (Ge 2005).
39
Table 5.1. Summary of 4C inputs and how to obtain them
Item
Detailed description
Width, depth, and length
Structural
Cooling pipe layout
Geometry
Foundation types (concrete or soil)
concrete placement temperature
cast rate
insulation methods
Construction
formwork material
form removal time
cooling process
Environmental ambient temperature, wind speed
and boundary
conditions
slump, w/c ratio, air content, density
Fresh concrete
specific heat, thermal conductivity, coefficient of
properties
thermal expansion
maturity and its relationship with heat development
E-modulus
Hardened
Poison ratio
concrete
Compressive strength
properties
Tensile strength
Creep
Source
Structure Design
Designed,
Measured,
or Assumed
Measured
or Collected
Collected
or Predicted
Measured
Measured or Predicted
4C default
Measured or Predicted
Measured or Predicted
Measured or Predicted
Table 5.2. Models used for prediction of concrete properties in 4C program
Source
E-modulus
(Ge 2005)
(Ge 2005)
Tensile strength
J(
For
(
)
Creep
For
(
)
(
-
)
(
)
) (Westman 1999)
Table 5.3 shows the output item comparison between 4C and ConcreteWorks, another computer
software package used by the research team in the first phase of these projects. Compared to
ConcreteWorks, 4C-Temp&Stress has capacity to build databases for structures, concrete,
formwork/insulation, and materials, etc., but users can only choose established concrete database
and geometry of concrete members in ConcreteWorks.
40
Table 5.3. Comparison of 4C outputs with ConcreteWorks
Output Items
4C ConcreteWorks
Max. temperature of the volume
x
x
Min. temperature of the volume
x
x
Max. temperature of specific point
x
Min. temperature of specific point
x
Max. temperature difference of the volume
x
Ambient temperature
x
x
Average temperature of the volume
x
Average temperature of specific point
x
The 4C program has the other advantage of presenting more detailed temperature data. In the 4C
program, the analysis at specific points could also be applied on maturity, strength, and stress
results demonstration. Not only are multiple choices to exhibit analysis results along the time
available, but showing iso-curves at a given time is also an advantage of 4C-Temp&Stress. (An
iso-curve is a curve along which the function has a constant value in the cross section of the
concrete structure.)
Furthermore, 4C also considers the effects of cooling pipes or heating wires, which are not
considered in ConcreteWorks. Users can define the cooling pipe/heating wires used in the project
and simulate thermal development more closely to the real construction. In addition, the 4CTemp&Stress software package is more effective in terms of calculation time than
ConcreteWorks, and a longer analysis period could be designed, while ConcreteWorks could
only consider a 14 day temperature prediction and a 7 day cracking potential prediction.
The following points could be considered as challenges for users of 4C-Temp&Stress:






4C software normally works in the Windows XP environment, and might be compatible with
Windows 7 with 32 bit, but not 64 bit
Comparing both programs, ConcreteWorks is free software and uses English units, which
makes the program more applicable in the US, while 4C is a commercial program with SI
units only
4C-Temp&Stress has more inputs, which require users to be more knowledgeable in order to
collect the information and make reasonable assumptions, while ConcreteWorks has many
defaults and does not require so much information to input
The other potential shortfall for 4C occurs when the volume of concrete becomes extremely
large, generated meshes are relatively fine, or cement content is increased to relatively high,
and the calculation for the analysis could not be extended for a relatively long period
4C ambient temperature inputs are not flexible and could only be assumed as sine-curve or
constant, while actual ambient temperature varies day by day, so that the prediction results
might be different from actual measurements
The 4C cross-section results viewer can be displayed only at the mid span along the longest
edge of the concrete and no diagonal or other perpendicular cross section results can be
analyzed and presented
41
CHAPTER 5. SOFTWARE CALIBRATION
5.1 Overview
This chapter details the calibration of ConcreteWorks and 4C-Temp&Sress through the use of
two case studies, the WB I-80 Missouri River Bridge and the US 34 Missouri River Bridge. The
following sections include a description of the case studies, the calibration of ConcreteWorks
and 4C-Temp&Stress for the WB I-80 Missouri River Bridge, the calibration of ConcreteWorks
and 4C-Temp&Stress for the US 34 Missouri River Bridge, and a discussion of the results.
5.2 Westbound I-80 Missouri River Bridge
The WB I-80 Missouri River Bridge consisted of 27 different mass concrete elements, as defined
by the Iowa DOT mass concrete developmental specification (DS-09047). The case study
consisted of the analysis of 21 mass concrete elements. Six elements were unable to be analyzed
because cooling pipes were utilized, and ConcreteWorks cannot analyze placement with cooling
pipes, or the thermal data that were provided were not sufficient to provide accurate results or a
valid comparison.
5.2.1 ConcreteWorks
5.2.1.1 Inputs Overview
The construction of the WB I-80 Missouri River Bridge was completed prior to the start of this
research. The thermal data from the construction of the mass concrete elements was provided by
the Iowa DOT. The data included the name of the element, placement date, placement start time,
placement completion time, and whether post cooling was utilized. In addition, the thermal data
provided hourly temperature readings of the air temperature, center temperature of the
placement, top surface temperature of the placement, and side surface temperature of the
placement.
To identify the concrete mix proportion, construction practices, and environmental conditions in
which the elements were placed, a survey of information was conducted. The surveyed
documents included examination of the bridge plans, thermal data from the bridge construction,
photos of the construction, thermal control plans, and mix designs. In addition, to identify how
the placements were constructed, interviews were conducted with personnel who worked on the
project, including contractors, project managers, contractor field engineers, and Iowa DOT
inspectors.
From the documents and interviews, a general understanding of the concrete mix proportion,
construction parameters, and environmental conditions of each placement was developed. The
input parameters used to complete the thermal analysis were developed to model the actual
conditions as accurately as possible with the information provided.
42
The development and values of the inputs used to complete the case study in ConcreteWorks is
discussed in the following sections. The inputs are divided into three sections: concrete mix
proportion, construction parameters, and environmental conditions.
5.2.1.2 Concrete Mix Proportion Inputs
The concrete mix proportion inputs include mixture proportion inputs, material properties, and
mechanical properties as defined by ConcreteWorks.
Mixture Proportion Inputs
Each placement on the project utilized the same concrete mix proportion. The concrete mix
proportion inputs were developed based on the mix proportion provided by the Ready Mixed
Concrete Co. of the Lyman-Richey Corporation, as shown in Table 5.4.
Table 5.4. Ready Mixed Concrete Co. mix design for WB I-80 Missouri River Bridge
Iowa Mass Concrete (5,000 psi) with Slag
Component
Amount
Price
Cement, IPF
420 lb
2.28
Slab GGBFS
207 lb
1.13
Water (263#)
0.42 lb/lb
4.21
Class V Sand-Gravel
1,586 lb
9.70
#557 Limestone
1,322 lb
7.93
Air Content
6.5%
1.75
Water Reducer
3 oz/100 lb
.00
High-Range Water Reducer 4-8 oz/100 lb
.00
27.00
Cement type IPF is a blended cement that contains approximately 75 percent type I cement and
25 percent class F fly ash by weight. The largest factor of fly ash affecting the heat generation of
concrete is the lime or CaO content. Class F fly ash is generally defined as having a CaO
percentage of less than 10 percent. The percentage of CaO used in the case study is 8.7 percent,
which is the value provided by Headwaters Resources, one of the main suppliers of fly ash in
Iowa (Headwaters Resources 2005).
Slag is available in three different grades, 80, 100, and 120, which identify the rate of strength
gain with grade 80 being the lowest. Grade 80 slag is not used commonly in general concrete
construction. ConcreteWorks assumes a slag grade of 120, which is a reasonable assumption for
the project. In addition, the water-reducing agents are assumed to be type F naphthalene, a highrange water reducer. The concrete mix proportion inputs used for all of the mass concrete
elements on the WB I-80 Missouri River Bridge as used in ConcreteWorks are listed in Table
5.5.
43
Table 5.5. Mixture proportion inputs for WB I-80 Missouri River Bridge
Input
Units
Value
Cement content
lb/yd3
315
lb/yd
3
264
Course aggregate content
lb/yd
3
1322
Fine aggregate content
Air content
lb/yd3
%
1586
6.5
Class F fly ash
Class F fly ash CaO
lb/yd3
%
105
8.7
Water content
Grade 120 slag
lb/yd3
207
Chemical admixture input
Water reducer*
*Naphthalene high-range water reducer (type F)
Material Property Inputs
The material properties of the concrete are dependent on the mix proportion of the concrete;
therefore, all the mass concrete elements have the same material properties. The Bogue
calculated values were provided by the Ash Grove Cement Company Louisville, Nebraska plant
for type I/II cement. The values were calculated by ASTM test method C114 and represent the
average values for cement produced between May 1 and May 31 of 2010. The values as input to
ConcreteWorks are listed in Table 5.6.
Table 5.6. Ash Grove Cement Company type I/II cement Bogue calculated values (Ash
Grove Cement Company 2010)
Compound Value (%)
C3S
59.73
C2S
13.25
C3A
6.05
C4Af
Free CaO
9.46
0.9
SO3
MgO
3
2.97
Na2O
0.13
K2O
0.63
The coarse aggregate type is listed in the Ready Mixed Concrete Co. mix design as limestone.
The fine aggregate type is siliceous river sand, which is the fine aggregate type used most
44
commonly in the area. Typical Iowa concrete has a coefficient of thermal expansion in the range
of 4.1 to 7.3 (10-6/°F) (Wang et al. 2008). The analysis utilized the value of a 4.1.
Table 5.7 shows the material properties used to model all of the elements from the WB I-80
Missouri River Bridge. The values that are denoted as ConcreteWorks default values are
believed to represent the actual material properties accurately. In addition, the cement hydration
properties were not altered from the ConcreteWorks default values.
Table 5.7. Material property inputs for the WB I-80 Missouri River Bridge
Input
Cement Type
Value
Type I/II
371.5 m2/kga
Blaine
Tons CO2
Bogue Calculated Values
Coarse Aggregate Type
Fine Aggregate Type
0.9a
Ash Grove I/IIb
Limestone
Siliceous River Sand
4.1*10-6
CTE
Concrete k
1.6 BTU/hr-ft/°Fa
Combined Aggregate Cp
0.20 BTU/lb/°Fa
a
denotes ConcreteWorks default value
denotes values provided in Table 5.8
b
Mechanical Property Inputs
The mechanical properties were assumed to be the same for all elements on the WB I-80
Missouri River Bridge. The mechanical property inputs for ConcreteWorks include the maturity
function, equivalent age elastic modulus inputs, equivalent age splitting tensile strength inputs,
and early age creep parameters. This case study utilizes the ConcreteWorks default values for all
inputs expect for the maturity function.
The maturity was defined using the logarithmic Nurse-Saul strength method. The Nurse-Saul
logarithmic equation is shown by equation 4.1.
(4.1)
Sm = a + b log(M)
where:
Sm = is the strength of the concrete
a = strength for the maturity index M = 1
b = slope of the line
M = maturity index
45
The Nurse-Saul equation relates the concrete compressive strength with the average maturity
index of the concrete. The logarithmic equation provides a simplistic relationship for strength
and maturity by utilizing a straight line to represent the maturity function on a logarithmic scale
(Carino and Lew 2001).
The constants, a and b, used to model all of the elements for the WB I-80 Missouri River Bridge
were taken as the average value of a and b calculated from the thermal results for each individual
placement. The constants for each individual placement were determined from the thermal,
maturity, and strength development data, and are shown in Table 5.8. These values were
averaged to determine the values used in each analysis, a = -9,609.7 psi and b = 3,450.1
psi/°F/hr.
Table 5.8. Calculated Nurse-Saul constants for each placement for the WB I-80 Missouri
River Bridge
Pier
1
1
1
2
2
2
2
3
3
3
3
4
4
4
4
5
5
5
5
6
6
Element
Footing
Stem/Column
Cap
Footing
Stem
Column
Cap
Footing
Stem
Column
Cap
Footing
Stem
Column
Cap
Footing
Stem
Column
Cap
Footing
Column
a (psi)
-9691.2
-5371.1
-5038
-8205.5
-10908
-6658.9
-8536.5
-11894
-11806
-9140.3
-9197.9
-9072.1
-11089
-8592.8
-8381.3
-11324
-12101
-9024.1
-9462.4
-11989
-12213
b (psi/°F/hr)
3462.8
2077.6
1947.3
3030.6
3850.9
2496
3135.6
4148.2
4153.6
3272.6
3345.1
3311.2
3928.2
3169.6
3076.1
3956.2
4166
3308.1
3438.9
4223.7
4253.5
5.2.1.3 Construction Parameter Inputs
The construction parameter inputs include the general inputs, shape inputs, dimension inputs,
and construction inputs.
46
General Inputs
The category of general input includes units, placement date, placement time, analysis setup,
state, and city. The general convention for units in the US is English units. The location of all the
placements is Omaha, Nebraska, where the bridge was actually constructed. The placement dates
and times were provided by the contractors, with the thermal data for each placement, and are
listed in Table 5.9. Placement start times that do not fall on the hour are rounded up to the
nearest hour, as required by ConcreteWorks.
Table 5.9. Placement date and time for each element of the WB I-80 Missouri River Bridge
Pier
1
1
1
2
2
2
2
3
3
3
3
4
4
4
4
5
5
5
5
6
6
Element
Footing
Stem/Column
Cap
Footing
Stem
Column
Cap
Footing
Stem
Column
Cap
Footing
Stem
Column
Cap
Footing
Stem
Column
Cap
Footing
Column
Date
10/20/08
12/4/08
1/23/09
11/19/08
1/9/09
2/18/09
3/20/09
10/30/08
11/21/08
1/23/09
2/25/09
11/4/08
12/10/08
3/5/09
3/20/09
2/3/09
2/17/09
3/31/09
5/5/09
11/4/08
1/6/09
Placement Start
Time
9:15 AM
9:45 AM
10:30 AM
10:30 AM
12:00 PM
8:30 AM
9:00 AM
3:30 PM
9:45 AM
9:00 AM
10:00 AM
12:45 PM
9:00 AM
8:00 AM
9:00 AM
12:30 PM
9:30 AM
8:00 AM
8:00 AM
7:00 AM
8:30 AM
Shape Inputs
ConcreteWorks provides six different shape options for mass concrete elements including
rectangular column, rectangular footing, partially submerged rectangular footing, rectangular
bent cap, T-shaped bent cap, and circular columns. To model the elements, all placements
defined as footings were input as rectangular footings, columns and stems were input as
rectangular columns, and caps were input as rectangular bent caps.
47
Dimension Inputs
The dimensional size of each element as provided by the final design plans of the bridge are
listed in Table 5.10.
Table 5.10. Dimensions of elements for the WB I-80 Missouri River Bridge
Pier
1
1
1
2
2
2
2
3
3
3
3
4
4
4
4
5
5
5
5
6
6
Element
Footing
Stem/Column
Cap
Footing
Stem
Column
Cap
Footing
Stem
Column
Cap
Footing
Stem
Column
Cap
Footing
Stem
Column
Cap
Footing
Column
Depth
(ft)
4.5
4
4
5
5
5
5
7.25
6
6
6
5
5
5
5
6.5
5
5
5
5.75
8.33
Width
(ft)
12
7
8.25
15
19
11
8.25
27
16
11
8.25
15
18
11
8.25
19
20
11
9.66
18
11
Length
(ft)
43
43
43
43
43
46
-
For rectangular columns and rectangular bent caps, ConcreteWorks assumes that the elements
are infinitely long and does not allow for the input of the element length. ConcreteWorks also
allows for elements that are submerged in water or soil formed. The WB I-80 Missouri River
Bridge did not have elements that were soil formed or submerged in water. Footings may be
analyzed as two- or three-dimensional (2D or 3D) to account for the length of the elements; our
models utilized the 2D analysis, and assumed the footings were infinitely long.
48
Construction Inputs
The available construction inputs in ConcreteWorks include the concrete placement temperature,
concrete age at form removal, formwork type, formwork color, blanket R value insulation,
surrounding temperature, curing method, and subbase material.
The fresh placement temperatures for each placement were not recorded by the contractors. For
this case study, the fresh placement temperature was taken to be the average of the initial thermal
sensor readings, or the average concrete temperature at hour zero.
The concrete age at form removal was taken as the time from the start of the placement, which
was provided by the contractors, to the end of thermal monitoring, assumed to be the
approximate time of form removal.
The type of formwork varied by placement and documentation could not be found that indicated
what kind of formwork was use for each placement. Photos found in construction records
indicated that both wood and steel forms were used. For the purposes of this analysis; it was
assumed that all placements were formed using wood formwork. Similarly, the exact insulation
used on each placement was not documented. The thermal control plans generally recommended
the use of one insulating blanket with an R value of 2.5. It was assumed that all of the
placements had an insulating blanket with an R value of 2.5.
The exact soil temperatures that the placements experienced were also not documented. It was
assumed that the soil temperature for the footings was the average ambient air temperature
during the 14 days the analysis was conducted. The average ambient air temperature was
provided by the National Weather Service historical data.
From interviews with the contractors and Iowa DOT inspectors, it was determined that none of
the placements utilized any curing methods. Therefore, the analysis was conducted without
curing for any placements.
From discussions with contractors and Iowa DOT inspectors, it was determined that the footings
were constructed on two different subbase conditions: clay and concrete. For footings that were
constructed above the water table, no seal coat was needed and the footing was poured directly
onto the clay-like material found in the riverbed. Footings that were constructed below that water
table required a concrete seal coat to slow water infiltration into the cofferdams. Therefore, the
subbase material was determined by examining the plans and identifying if the bottom of the
footings were above or below the water table. Stems, columns, and pier caps do not require
subbase inputs, as they are assumed to be infinitely long.
Table 5.11 shows the construction inputs for the WB I-80 Missouri River Bridge. In addition to
these parameters, the placements are assumed to have used wooden formwork and an insulating
blanket with an R value of 2.5.
49
Table 5.11. Construction inputs for the WB I-80 Missouri River Bridge
Pier
1
1
1
2
2
2
2
3
3
3
3
4
4
4
4
5
5
5
5
6
6
Element type
Footing
Stem/Column
Cap
Footing
Stem
Column
Cap
Footing
Stem
Column
Cap
Footing
Stem
Column
Cap
Footing
Stem
Column
Cap
Footing
Column
Fresh
Placement
Temperature
(°F)
60.8
55.1
53.9
63.8
57.8
64.1
61.1
68.6
56.6
56.8
66.2
68.6
56.6
66.5
61.4
45.2
61.4
67.7
67.7
71.6
60.5
Concrete
Soil
Age at Form Temperature Subbase
Removal (hr)
(°F)
Material
198
56
Concrete
94
101
289
41
Clay
236
118
147
378
56
Clay
284
156
166
193
66
Clay
323
146
140
347
11
Clay
316
148
153
373
66
Concrete
346
-
5.2.1.4 Environmental Condition Inputs
The environmental condition inputs available in ConcreteWorks include the temperature, wind
speed, percent cloud cover, relative humidity, and yearly temperature. To provide for a more
accurate case study, the actual weather conditions for each placement were utilized in
ConcreteWorks. The maximum and minimum daily temperatures were input as provided by the
National Weather Service historical data archive for Omaha, Nebraska. All other weather data
were set as the default.
5.2.1.5 Sensor Location Corrections
For each placement constructed, there were sensors installed at three locations: center of the top
surface, center of the side surface closest to the center, and center of the placement. The exact
location of each sensor used during construction is unknown. It is assumed that the surface
sensors were placed at the exact center of the respective surfaces with three inches of concrete
50
cover and that the center sensor was installed at the exact center of the placement. These
assumptions were developed from interviews with the contractors and the thermal control plans.
ConcreteWorks calculates the thermal properties of mass concrete placements at discrete points
throughout the placement with time. The spacing of the discrete points in the depth and length
direction is approximately 4 to 12 inches, depending on which placement was being addressed.
To compare the analysis results generated by ConcreteWorks to the actual results, three points
were utilized. The three points correspond to the assumed sensor locations used during
construction. As the discrete temperature points do not correspond exactly with the assumed
sensor locations, a linear approximation between the surrounding points is used to determine an
effective temperature at the desired locations as shown by Figure 5.1.
Figure 5.1. ConcreteWorks thermal analysis discrete temperature point layout
5.2.1.6 Results
The results of the WB I-80 Missouri River Bridge case study are listed in Table 5.12, Table 5.13,
Table 5.14, and Table 5.15. The results are separated into separate tables for each placement type
(footings, stems, columns, and caps) to show the accuracy of ConcreteWorks for each placement
type. Each table shows the maximum temperature and maximum temperature difference
determined from the ConcreteWorks analysis compared to the actual recorded maximum
temperature and maximum temperature difference. In addition, each table also indicates negative
51
errors, representing an underestimation by ConcreteWorks, and the positive errors, representing
an overestimation by ConcreteWorks.
Table 5.12. WB I-80 case study thermal results - footings
Maximum Temperature
(°F)
Pier Actual ConcreteWorks Error
1
131
119.2
-11.8
2
134.6
126.5
-8.1
3
153.5
147.1
-6.4
4
142
139.3
-2.7
5
136.4
101.5
-34.9
6
156.2
144.6
-11.6
Maximum Temperature Difference
(°F)
Actual ConcreteWorks
Error
35.1
23.3
-11.8
35.1
43.5
8.4
59.4
56.3
-3.1
38
47.8
9.8
53.1
34.4
-18.7
52.2
51.2
-1.0
Table 5.13. WB I-80 case study thermal results - stems
Maximum Temperature
Maximum Temperature Difference
(°F)
(°F)
Pier Actual ConcreteWorks Error Actual
ConcreteWorks
Error
1
97.7
92.6
-5.1
15.3
22.5
7.2
2
136.4
111.5
-24.9
31.5
40.4
8.9
3
139.1
119.8
-19.3
24.3
36.8
12.5
4
135.5
112
-23.5
40.5
39.8
-0.7
5
140.9
120.3
-20.6
43.2
39.7
-3.5
Table 5.14. WB I-80 case study thermal results - columns
Maximum Temperature
Maximum Temperature Difference
(°F)
(°F)
Pier Actual ConcreteWorks Error Actual ConcreteWorks
Error
1
97.7
92.6
-5.1
15.3
22.5
7.2
2
126.5
121.1
-5.4
38.7
37
-1.7
3
128.3
112.9
-15.4
28.7
42.4
13.7
4
140.9
133.1
-7.8
50.4
34.9
-15.5
5
142
130.6
-11.4
39.5
34.3
-5.2
6
150.8
132.2
-18.6
50.4
48.8
-1.6
52
Table 5.15. WB I-80 case study thermal results - caps
Maximum Temperature Difference
Maximum Temperature (°F)
(°F)
Pier Actual ConcreteWorks Error Actual ConcreteWorks
Error
1
102.2
92.5
-9.7
24.7
22.5
-2.2
2
139.1
126.8
-12.3
49.5
28.5
-21.0
3
146.3
132
-14.3
54.9
44.9
-10.0
4
129.2
127.1
-2.1
37.8
28.5
-9.3
5
140
141.3
1.3
34.2
30.3
-3.9
Appendix C shows the results of each individual placement. The graphs in Appendix C show the
comparison of the analysis results to the actual recorded data for the three discrete sensor
locations with time.
5.2.1.7 Discussion
A statistical analysis of the maximum temperature error and maximum temperature difference
error is provided in Table 5.16 and Table 5.17. The statistical analysis includes the range of
errors, the error mean, and the standard deviation of the error for both the maximum temperature
and the maximum temperature difference for each element type.
Table 5.16. Maximum temperature error statistical analysis of the WB I-80 Missouri River
case study
Element type
Footings
Stems
Columns
Caps
Minimum
error (°F)
-34.9
-24.9
-18.6
-14.3
Maximum
error (°F)
-2.7
-5.1
-5.1
1.3
Error mean
(°F)
-12.6
-18.7
-10.6
-7.4
Error
standard
deviation (°F)
11.5
7.9
5.5
6.7
Table 5.17. Maximum temperature difference error statistical analysis of the WB I-80
Missouri River case study
Element
Type
Footings
Stems
Columns
Caps
Minimum
error (°F)
-18.7
-3.5
-15.5
-21.0
Maximum
error (°F)
9.8
12.5
13.7
-2.2
Error mean
(°F)
-2.7
4.9
-0.5
-9.3
53
Error
standard
deviation (°F)
11.1
6.7
10.1
7.4
The results show that, under the conditions of this case study, ConcreteWorks underestimates the
maximum temperature of a placement; the average error for the maximum temperature of all
placements is 12.3°F. On average, ConcreteWorks underestimated the maximum temperature
difference of a placement by 1.9°F for all placement types.
The results of the WB I-80 Missouri River Bridge case study show that ConcreteWorks is
capable of predicting the general trends of the maximum temperature and maximum temperature
difference of mass concrete placements for Midwest border bridges to a reasonable degree. The
WB I-80 case study was also able to confirm the ability of ConcreteWorks to predict the
temperature development of distinct points accurately in a mass concrete element, as shown by
the individual placement thermal results. However, it appears that it would be prudent to make
adjustments to the results because ConcreteWorks usually underestimates the maximum
temperature and the maximum temperature difference, which is not conservative.
The error in the ConcreteWorks analysis might be attributed to differences between assumed and
actual construction parameters. The lack of knowledge of the formwork type, insulation
properties, and sensor locations is likely to be responsible largely for the analysis errors.
Additional errors for the top surface sensors for the footings and columns arises from the
ConcreteWorks assumption that the top surfaces are wet-cured. Although white pigmented
curing compound or wet curing of top surfaces is required by specification, the researchers could
not verify whether or not that this was done in all cases.
5.2.2 4C-Temp&Stress
5.2.2.1 Inputs
A total of 26 concrete members in the WB I-80 Bridge were selected for this case study. None of
these units utilized cooling pipes. There are 7 footings, 8 columns, 7 stems, and 5 caps. This was
done to keep the properties consistent to enhance comparison. These units had different
dimension size, environmental temperature, and formwork removal time. However, the mix
design and insulation material are presumed to be the same. The general inputs are described in
Table 5.18.
54
Table 5.18. Concrete properties and material properties inputs used in I-80 Bridge case
study
Description
Concrete Volume
Concrete Properties
Input Value
Notes
101mm
Obtained from data collection
0.42
Obtained from data collection
6.50%
Obtained from data collection
Measured density
2320Kg/m^3
Obtained from data collection
Specific heat
0.84Kj/kg/°c
Obtained from data collection
Thermal conductivity
13
Obtained from data collection
Act. Energy factor 1
33500 J/mol
Default in 4c program
Act. Energy factor 2
1470 J/mol/°c
Default in 4c program
Slump
W/c ratio
Air content
Material Properties
Maturity vs. Heat
development data
Maturity vs. Emodulus
Maturity vs. Poison
ratio
CW'S default value
Maturity vs.
Compressive strength
Maturity vs. Tensile
strength
Creep
W/o cpipes: total:650 KJj/Kg, time :28h,
curvature: 0.7
W/ cpipes: total:490 KJ/Kg, time :28h,
curvature: 0.7
Total:40000 Mpa, time :15h, curvature:
0.8 cementitious material
Total: 0.17, time: 22.4 hr, curvature :1,
fresh: 0.34
0.00000736 /c
Total:50Mpa, time :70h, curvature: 0.7
Total:4.5Mpa, time :70h, curvature: 0.41
Based on temp. development data
from collected data
Based on model prediction
Default value in computer program
Obtained from data collection
Based on estimated compressive
strength data from collected data
Based on model prediction
Based on model prediction
5.2.2.2 Results and Discussion
Verification for the 4C program was conducted through the analysis of 26 mass concrete
elements (without cooling pipes) selected from the WB I-80 Bridge. The results are presented in
Figures 5.2 and 5.3. Figure 5.2 provides a typical comparison between the measured and
predicted temperature development for the Pier 1 footing concrete. When the age is less than 3
days (72 hours), the prediction values are generally consistent with those measured. However,
the predicted values were lower than those measured for ages greater than 3 days. The
discrepancy is 25% at 200 hours.
55
70
4C Predicted Max. Temp.
Measured Max. Temp.
4C Predicted Temp. Diff.
Measured Temp. Difference
60
Temp.(°C)
50
40
30
20
10
0
0
50
100
Time(hr)
150
200
Figure 5.2. Comparison between the measured and 4C predicted temperatures (Pier 1
footing of WB I-80 Bridge)
Figure 5.3 shows the relationship between the measured and predicted maximum temperatures
for the 26 concrete members analyzed. There are 780 temperature data points in Figure 5.3, 30 of
which were selected from each structure member (footing, column, stem, or cap). As observed in
Figure 5.3, most predictions are acceptable since their data points are close to the line of
equality, suggesting that the 4C prediction differs little from the measured data. However, there
are apparent outliers that are shown as light gray data points in Figure 5.3.
56
Outliers
Outliers
Figure 5.3. Line of equality plot for 780 data points of maximum temperature results from
measured temperatures and 4C predicted temperatures
To identify these outliers, Figure 5.4 provides plots of the discrepancies between the 4C
predicted and measured maximum temperatures. The data are categorized with the types of
structural elements at selected time analysis points (0, 3, 6, …87 hours) to ensure there are
enough data points to provide a reasonable analysis, but not so many as to create a heavy
calculation load. The figure shows that stem elements have larger discrepancies between the
measured and predicted temperatures compared to other elements, and that the discrepancies
increase with time. The outliers (light gray data points) for the stem elements are shown in
Figure 5.3. The outliers indicate that stems may not be modeled with complete accuracy by 4C,
due to the simplification of the shape and size of the stem elements in the 4C model.
57
Pier 5
Pier 2
Pier 3
Pier 4
Pier 9
0
15
30
45
Time (Hours)
60
75
90
Figure 5.4. Temperature discrepancy plot for various structural elements
A statistical analysis of the temperature discrepancies was conducted to further evaluate the
agreement between the 4C predictions and the field measurements for concrete at early age (0 to
72 hours). This period was selected because the maximum concrete temperature and the
maximum temperature difference generally develop during this time. The outliers were
eliminated before this analysis. The null hypothesis in this case is that the mean of the
discrepancies is equal to 0, that is that the prediction will be accurate.
H0:
=
Ha:
The results indicate that the p-values of the H0 are larger than 0.05, which indicates that we do
not reject the null hypothesis. That is, the temperature predictions from the 4C program are not
significantly different from the measurements. During this period, the confidence level of the
prediction is within 95%.
4C can provide iso-curve development during the analysis period. Iso-curve results for the case
study Pier 3 footing with cooling pipes are shown below at 48 hours. Figure 5.5 shows the isocurve of temperature development for the right third of the cross-section (or cut view) of the
concrete member at 48 hours, when the concrete reached peak temperature during the analysis
period.
58
Cut view
Concrete member
Figure 5.5. Sample temperature development iso-curve results for right-third cross section
of Pier 3 footing with cooling pipe applied at 48 hours (not to scale)
The highest stress/strength ratio occurs during the first 24 hours at edges and corners of the
concrete member. With passing time, the higher stress/strength ratio is likely to appear at the
center of the structure. Examples of iso-curve results on stress/strength ratios are shown in
Figure 5.6 and Figure 5.7. The iso-curve graphic results are generated by the 4C program. The
user could zoom in and out on the cross section to get readable iso-curve results.
59
Cut view
Concrete member
Figure 5.6. Sample tensile stress/strength iso-curve results for lower right corner of cross
section of Pier 3 footing with cooling pipe applied at 12 hours (not to scale)
Cut view
Concrete member
Figure 5.7. Sample tensile stress/strength iso-curve results for lower right corner of cross
section of Pier 3 footing with cooling pipe applied at 168 hours (not to scale)
60
5.3 US 34 Missouri River Bridge
The US 34 Bridge over the Missouri River has several mass concrete elements as defined by the
Iowa DOT mass concrete developmental specification (DS-09047). The elements include
footings, columns, and caps that were constructed with and without cooling pipes.
Through the duration of this research, a total of 19 mass concrete elements have been completed.
Of the 19 elements, four used cooling pipes. This case study will examine the 15 placements that
did not use cooling pipes given ConcreteWorks is not capable of analyzing mass concrete
placements with cooling pipes.
The elements have a least dimension ranging in size from 5.5 to 6.5 feet. Many of the elements
have similar dimensions as several piers have four footings, columns, and caps with the same
dimensions. In total, six of the elements are footing, eight are columns, and one is a pier cap.
5.3.1 ConcreteWorks
5.3.1.1 Inputs Overview
While the WB I-80 Missouri River Bridge was not constructed during the time that this research
was conducted, the US 34 Missouri River Bridge was constructed partially during the time this
research was conducted. The inputs for the case study were developed largely from firsthand
observations of the construction of the elements. Other sources of information for the
development of the inputs included final bridge design plans, thermal control plans, field data
reports, and interviews with the project superintendent.
5.3.1.2 Concrete Mix Proportion Inputs
The US 34 Missouri River Bridge utilized the same concrete mix proportion that was utilized on
the WB I 80 Missouri River Bridge. Given that the mix proportions were the same, it is assumed
that the material and mechanical properties of the concrete will be similar. For that reason, all
inputs for the mix proportion, material properties, and mechanical properties that were used to
model the previous case study were used to model the US 34 Missouri River Bridge case study.
5.3.1.3 Construction Parameter Inputs
The largest difference between the two case studies is the construction parameters. The US 34
case study includes firsthand reports of the actual construction conditions.
General Inputs
The category of general inputs includes units, placement date, placement time, analysis setup,
state, and city. The location of the placements on the US 34 case study is taken as Omaha,
61
Nebraska, which is approximately 15 miles north of the actual bridge location. The placement
date and start time was supplied by the contractor in the thermal data field report and is included
in Table 5.19. Placement start times that do not fall on the hour are rounded up to the nearest
hour, as required by ConcreteWorks.
Table 5.19. Placement date and time for each element of the US 34 Missouri River Bridge
Pier
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
Element
Footing - A
Footing - B
Footing - C
Footing - D
Column - A
Column - B
Column - C
Column - D
Cap
Footing - C
Footing - D
Column - A
Column - B
Column - C
Column - D
Placement
Date
3/8/2012
3/8/2012
3/2/2012
3/2/2012
3/21/2012
3/21/2012
3/12/2012
3/12/2012
4/5/2012
4/11/2012
4/11/2012
5/3/2012
5/3/2012
4/25/2012
4/25/2012
Placement
Start Time
2:00pm
2:00pm
2:00pm
2:00pm
9:15am
9:15am
10:00am
10:00am
2:00pm
2:00pm
2:00pm
9:00am
9:00am
8:00am
8:00am
Shape Inputs
To model the elements, all placements defined as footings were input as rectangular footings,
columns were input as circular columns, and caps were input as rectangular bent caps.
Dimension Inputs
The dimensional size of each element was developed from the final bridge plans that were
provided by the Iowa DOT. The dimensions of each placement required to run the
ConcreteWorks analysis is provided in Table 5.20, with the column diameter defined as the
width. ConcreteWorks assumes that columns and caps are infinitely long in comparison to the
width and depth and therefore do not require a length input. None of the elements analyzed were
submerged in water or soil formed. Similar to the WB I-80 case study, the footings are analyzed
as two-dimensional elements.
62
Table 5.20. Dimensions of elements for the US 34 Missouri River Bridge
Pier
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
Element
Footing - A
Footing - B
Footing - C
Footing - D
Column - A
Column - B
Column - C
Column - D
Cap
Footing - C
Footing - D
Column - A
Column - B
Column - C
Column - D
Depth (ft) Width (ft) Length (ft)
5.5
12
12
5.5
12
12
5.5
12
12
5.5
12
12
5.5
5.5
5.5
5.5
5.5
5.75
6.5
15
22
6.5
15
22
5.5
5.5
5.5
5.5
-
Construction Inputs
The construction inputs available in ConcreteWorks include curing method, subbase material,
insulating blanket R value, concrete fresh placement temperature, soil temperature, concrete age
at formwork removal, formwork type, and formwork color.
It was observed and confirmed through interviews with the contractor that no curing methods
were implemented on the placements of interest. No curing methods were defined in
ConcreteWorks to complete the analysis.
Pier 2 and Pier 3 were located outside of the river and did not require a seal coat. It was observed
that the soil underlying the concrete was similar to that of clay covered with a layer of gravel.
Given the subbase material options that are available are limited, the clay subbase material was
utilized.
Each of the placements that were analyzed for the US 34 case study utilized one layer of
insulating blankets attached to the exterior sides of the formwork and on the top of the
placements. It was concluded through discussions with the contractors and inspections of the
insulating blankets that the effective insulating R value of the blankets was approximately 2.5.
To complete the analysis, it was assumed that all placements were covered on all sides with an
insulating blanket with an R value of 2.5.
The concrete fresh placement temperature, soil temperature, concrete age at formwork removal,
and formwork type as input into ConcreteWorks are listed in Table 5.21.
63
Table 5.21. Construction inputs for the US 34 Missouri River Bridge
Fresh
Placement
Soil
Element
Temperature Temperature
Pier Type
(°F)
(°F)
2
Footing - A
55
46.3
2
Footing - B
55
46.3
2
Footing - C
55
38.6
2
Footing - D
55
38.6
2
Column - A
65
2
Column - B
65
2
Column - C
60
2
Column - D
60
2
Cap
68
3
Footing - C
64
55
3
Footing - D
64
55
3
Column - A
72
3
Column - B
72
3
Column - C
72
3
Column - D
72
* Wood was used to form the bottom of the cap
Concrete
Age at Form
Removal
(hr)
157
157
182
230
136
136
112
156
138
207
207
91
91
115
115
Formwork
Material
Wood
Wood
Wood
Wood
Steel
Steel
Steel
Steel
Steel*
Wood
Wood
Steel
Steel
Steel
Steel
The fresh placement temperature of the concrete utilized in the analysis was measured by the
contractor at the time when the concrete arrived at the jobsite. The soil temperature used to
model the footings was taken to be the average daily temperature over the time in which the
placements were thermally monitored.
The time of formwork removal is approximately equal to the time at which the thermal
monitoring of the placements ceased. Therefore, the concrete age at formwork removal was
taken as the duration of time from the start of the pour to the final thermal reading of the
concrete.
The formwork materials were observed and documented for the US 34 case study, unlike the WB
I-80 case study. It was observed that the footings utilized wooden formwork and that the
columns utilized steel formwork. The cap utilized steel formwork to form the sides of the
placement and wood formwork for the bottom. It was also noted that all of the steel formwork
was yellow in color.
5.3.1.4 Environmental Conditions Inputs
Similar to the WB I-80 case study, the US 34 case study utilized the actual ambient air
temperatures as determined from the National Weather Service historical data archive for Omaha
64
Nebraska to complete the case study. In addition, all other environmental conditions were left as
the default values. The ConcreteWorks default values are calculated from the start date and time
of placement that were input and are based off the previous 30 years of historical weather data.
5.3.1.5 Sensor Location Corrections
While firsthand observations of the construction of the mass concrete placements from the US 34
bridge were conducted, the exact sensor locations could not be measured because of safety
concerns. It was observed that, in general, the sensors were placed in locations similar to those
described by the WB I-80 case study. To provide the most accurate data, the ConcreteWorks
analysis results were adjusted to match the sensor locations described by the WB I-80 case study.
The thermal sensor locations for the US 34 Bridge circular columns varied compared to those for
the WB I 80 Bridge. Two sensor locations were utilized for the circular columns: one at the
center of the column and one at the side surface. It was assumed that the center sensor was
placed at the exact center of the placement, and the side sensor was located at an arbitrary
location around the perimeter of the column with three inches of concrete cover.
For the footings and caps, it is assumed that one sensor was located at the exact geometric center
of the placement, one in the center of the top surface with three inches of concrete cover, and one
in the center of the side surface closest to the center with three inches of concrete cover.
5.3.1.6 Results
The results of the US 34 Missouri River Bridge case study are shown in Table 5.22, Table 5.23,
and Table 5.24. The results are broken down into three tables, separating the results by element
type. For each placement, the maximum temperature and maximum temperature difference is
provided for the actual recorded data and the ConcreteWorks analysis. In addition, the
temperature errors are also listed. A negative error represents an underestimation by
ConcreteWorks and a positive error represents an overestimation.
Table 5.22. US 34 case study thermal results - footings
Maximum Temperature
Maximum Temperature Difference
(°F)
(°F)
Pier Footing Actual ConcreteWorks Error Actual ConcreteWorks
Error
2
A
127.4
118.7
-8.7
21.6
28.2
6.6
2
B
129.2
118.7
-10.5
28.8
28.2
-0.6
2
C
129.2
117.2
-12
41.4
33.3
-8.1
2
D
127.4
117.2
-10.2
30.6
33.2
2.6
3
C
143.6
139.3
-4.3
46.8
40.6
-6.2
3
D
147.2
139.3
-7.9
45
40.6
-4.4
65
Table 5.23. US 34 case study thermal results - columns
Maximum Temperature
Maximum Temperature Difference
(°F)
(°F)
Pier Column Actual ConcreteWorks Error Actual ConcreteWorks
Error
2
A
134.6
123
-11.6
23.4
37.8
14.4
2
B
-15.2
14.4
138.2
123
23.4
37.8
2
C
-11.5
14.7
129.2
117.7
18
32.7
2
D
-16.9
3.9
134.6
117.7
28.8
32.7
3
A
-29.5
3.9
147.2
117.7
28.8
32.7
3
B
-31.3
1.7
149
117.7
36
37.7
3
C
-2
27.1
143.6
141.6
16.2
43.3
3
D
-9.2
34.4
150.8
141.6
9
43.4
Table 5.24. US 34 case study thermal results - cap
Maximum Temperature
Maximum Temperature Difference
(°F)
(°F)
Pier Actual ConcreteWorks Error Actual ConcreteWorks
Error
2
-16.7
11.2
138.2
121.5
36
47.2
A comparison of each individual placement with time is provided in Appendix D. The graphs in
the appendix show the comparison of the analysis results to the actual recorded data for the three
discrete sensor locations with time.
5.3.1.7 Discussion
A statistical analysis of the temperature prediction error was developed for the maximum
temperature and maximum temperature difference as shown in Table 5.25 and Table 5.26,
respectively. The statistical analysis includes the range, mean, and standard deviation of the
temperature prediction error. The statistical analysis is separated by element type. For the cap
element type, the statistical analysis is arbitrary, as only one cap was analyzed.
Table 5.25. Maximum temperature error statistical analysis of US 34 Missouri River case
study
Element
Type
Minimum
Error
(°F)
Maximum
Error
(°F)
Error
Mean
(°F)
Error
Standard
Deviation (°F)
Footings
Columns
Caps
-12.0
-31.3
-16.7
-4.3
-2.0
-16.7
-8.9
-17.7
-16.7
2.7
25.8
-
66
Table 5.26. Maximum temperature difference error statistical analysis of US 34 Missouri
River case study
Element
Type
Footings
Columns
Caps
Minimum Maximum Error
Error
Error
Error
Mean
Standard
(°F)
(°F)
(°F) Deviation (°F)
-8.1
6.6
-1.7
5.6
1.7
34.4
14.3
13.7
11.2
11.2
11.2
-
The results of the US 34 case study confirmed that ConcreteWorks generally underestimated the
maximum temperature of a placement for the given case study. On average for all placement
types, the average maximum temperature error is 13.2°F.
Similar to the WB I-80 case study, ConcreteWorks both over- and under-estimates the maximum
temperature difference compared to the actual field data. On average for all placements types, the
average maximum temperature difference prediction error is 6.9°F.
The results of the US 34 Missouri River Bridge case study show that ConcreteWorks is capable
of predicting the general trends of the maximum temperature and maximum temperature
difference of placements to a reasonable degree. In addition, the results show that
ConcreteWorks is capable of predicting the thermal development of placements at discrete
locations with time to a reasonable degree. Adjustments should be considered to address
recurring discrepancies between the predicted and actual temperatures. The results of the US 34
Missouri River Bridge case study confirm the results of the WB I-80 Missouri River Bridge case
study.
5.3.2 4C-Temp&Stress
5.3.2.1 Inputs
In the US 34 Bridge case study, 6 footings, 4 columns, and 1cap were analyzed. Sample results
of the Pier 4 footing using cooling pipes are presented below. The mix design and insulation
material are the same as those for the I-80 Bridge. The dimensional size, environmental
temperature, and construction procedures are shown in Table 5.27.
Table 5.27. 4C-Temp&Stress Inputs
Pier 4 footing
Dimensional Size(ft×ft×ft)
51×20×6 ft
Ambient Temp(F)
max:2°C(-37.8°F)
Fresh Place. Temp.
15.6°C(60°F)
Insulation material
Same as I-80 Bridge
Form removal time
200 hours
67
Insulation removal
168 hours
5.3.2.2 Results
The analysis of the concrete units resulted in findings that were similar to those for the I-80
Bridge. The discrepancies between 4C predicted and measured values are acceptable. Sample
results for the Pier 4 footing are shown in Figure 5.8.
160
140
120
Temp.(F)
100
80
4C Predicted Max. Temp.
Measured Max. Temp.
4C Predicted Max. Temp. Diff
Measured Max. Temp.Diff.
60
40
20
0
0
50
100
150
200
Times(hr)
Figure 5.8. Pier 4 footing temperature results for US 34 Bridge
The stress/strength ratios (σt/ft) for the Pier 4 footing are shown in Figure 5.9. High cracking
potential occurs when the σt/ft approaches unity. The final set of fresh concrete with fly ash
occurs generally 10 to 13 hours after placing. During the first 12 hours, the concrete is still
hardening and is relatively weak; the concrete is still restrained by substructure and formwork.
Even the tensile stress/strength ratio is large within the first 10 to 13 hours; the concrete is likely
to be too plastic or elastic to propagate cracks (Ge and Wang 2003).
Other actions that may delay the setting time include decreasing concrete temperature, using
slag, excessive plasticizer, and water-to-cement ratio. The peak stress/strength ratio occurs at
approximately 20 hours after casting, and this might occur after the concrete final set.
After final set, the concrete temperature keeps rising and the concrete will experience peak
temperature at around 48 hours. A large temperature difference may occur at this time, which
results in a large stress/strength ratio. Thus, the stress/strength ratio during 24 to 48 hours should
be considered as important criteria on evaluation of mass concrete thermal cracking when a
structure is placed on the soil substructure.
68
1
σt/ft Ratio
0.8
0.6
0.4
0.2
0
0
50
100
150
TIme(hr)
Figure 5.9. Pier 4 footing σt/ft ratio results for US 34 Bridge
69
200
CHAPTER 6. SENSITIVITY STUDY
6.1 Overview
This chapter provides a sensitivity study of parameters having the largest effect on the thermal
development of mass concrete. Two separate case studies are documented utilizing
ConcreteWorks and 4C-Temp&Stress. The following sections provide the ConcreteWorks
sensitivity study results, the 4C-Temp&Stress sensitivity study results, and a discussion of the
results.
6.2 ConcreteWorks Sensitivity Study
6.2.1 Overview
The early age development of mass concrete is affected by numerous mix proportion,
construction, and environmental factors. To design and construct a mass concrete element
properly, it is necessary to have an understanding of how each parameter affects the development
of the placement.
The purpose of this chapter is to investigate parameters that are believed to have the largest
effect on the development of mass concrete placements typical for Midwest border bridges. The
parameters were selected through a literature review of common practices used in the US to
reduce the risk of thermal damage. ConcreteWorks was utilized to explore thermal effects of the
selected parameters. The parameters that were investigated in this study and the classification of
each are shown in Table 6.1.
Table 6.1. Sensitivity parameter list and classification
Parameter
Group
Construction
Environmental
Mix Proportion
Parameter
Dimensional size
Fresh placement temperature
Curing method
Forming method
Formwork removal time
Subbase
Sensor Location
Ambient air temperature
Cement content
Fly ash substitution
GGBFS substitution
Combined class F fly ash and GGBFS substitution
70
The first section of this chapter describes the baseline inputs that were used to complete the
sensitivity study. The second section of the chapter provides the results for each of the
parameters. The final section of the chapter discusses the results of the sensitivity study.
6.2.2 Baseline Inputs
The mix proportion, construction, and environmental conditions affect the development of mass
concrete placements differently. To capture a characteristic response to a change in a selected
parameter, typical baseline conditions were selected in an attempt to model a standard mass
concrete placement found on a Midwest border bridge. To assure realistic inputs, an element was
selected from the WB I-80 Missouri River Bridge project. The Pier 3 footing was selected to be a
reasonable representation of an average mass concrete placement.
The baseline inputs for this sensitivity study are similar to those utilized in the case study for the
Pier 3 footing and are listed in Table 6.2 with additional values supplied in Table 6.3 and Table
6.4. The differences between the baseline conditions of the sensitivity study and the inputs used
for the case study of the Pier 3 footing are the Nurse-Saul values for the concrete maturity and
the sensor location corrections. For the sensitivity study, the Nurse-Saul values used were the
values that were calculated from the data from the Pier 3 footing only, not the average value for
all placements, as in the case study.
In addition, there were no corrections made for the sensor locations. The maximum temperature
and maximum temperature difference in the placement is calculated from all discrete points in
the placement. Therefore, the maximum temperature difference results are substantially higher
than those from the case study, resulting from the minimum temperature occurring at the surface
of the placement without concrete cover.
71
Table 6.2. Sensitivity study baseline inputs
Group
Member Type
Input
Member Type
Placement Time
Placement Date
General
Life Cycle Duration
Location
Shape
Shape
Width
Length
Dimensions
Depth
Sides
Analysis
Cement Content
Water Content
Coarse Aggregate
Fine Aggregate
Air Content
Mix Proportion
Class C Fly Ash
Class F Fly Ash
CaO%
GGBFS
Admixture
Cement Type
Blaine
Tons CO2/Tons Clinker
Bogue Values
Coarse Aggregate
Material
Fine Aggregate
Properties
Hydration Calculation Properties
CTE
Concrete k
Aggregate Cp
Maturity Method
Nurse-Saul (a)
Nurse-Saul (b)
Mechanical
Elastic Modulus
Splitting Tensile Strength
Creep
Fresh Placement Temperature
Form Removal Time
Forming Method
Construction
Form Color
Blanket R Value
Soil Temperature
Footing Subbase
Environment
All
Corrosion Inputs All
a – denotes values listed in Table 6.3
b – denotes values listed in Table 6.4
Baseline Inputs
Mass Concrete
3:30 PM
10/30/2008
75 years
Omaha, Nebraska
Rectangular Footing
27'
43'
7.25'
NA
2D
315 lb/cy
264 lb/cy
1322 lb/cy
1586 lb/cy
6.50%
0 lb/cy
105 lb/cy
8.70%
207 lb/cy
Naphthalene High Range Water Reducer
I/II
371.5m^2/kg
0.9
Ash Grove Type I/IIa
Limestone
Siliceous River Sand
Default
4.1*10^-6 /°F
1.6 BTU/hr/ft/°F
0.2 BTU/lb/°F
Nurse-Saul
(-)11894 psi
4148.2 psi/°F/Hr
Default
Default
Default
68.9 degrees F
312 hours
Wood
Natural Wood
2.5
49 degrees F
Clay
Actual Max/Min for 10/30/08b
Default
72
Table 6.3. Ash Grove type I/II Bogue calculated values
Bogue
Percent
Value
(%)
C3s
59.73
C2S
13.25
C3A
6.05
C4AF
9.46
Free CaO
0.9
SO3
3
MgO
2.97
Na2O
0.13
K2O
0.63
Table 6.4. Actual maximum and minimum temperature for 10/30/08-11/13/08
Date
10/30/2008
10/31/2008
11/1/2008
11/2/2008
11/3/2008
11/4/2008
11/5/2008
11/6/2008
11/7/2008
11/8/2008
11/9/2008
11/10/2008
11/11/2008
11/12/2008
11/13/2008
Maximum Minimum
(°F)
(°F)
72
40
70
39
68
35
76
48
79
58
74
57
70
47
49
36
38
32
34
28
38
25
36
26
43
34
39
34
54
37
6.2.3 Results
This section contains a description of the range for each parameter used in the sensitivity study
and the results for each parameter.
6.2.3.1 Dimensional Size
The range of dimensions used in the study represents typical mass concrete element sizes. The
sensitivity study looked at the effect of a change in depth, width, and length of a placement
73
independently, holding the other dimensions constant. The list of placement dimensions analyzed
in the sensitivity study, grouped by the dimension changed, is provided in Table 6.5.
Table 6.5. Dimensional size parameter ranges
Parameter Depth Width Length
Changed
(ft)
(ft)
(ft)
5
27
43
7.25*
27
43
Depth
10
27
43
15
27
43
20
27
43
7.25
10
43
7.25
20
43
Width
7.25
27*
43
7.25
30
43
7.25
40
43
7.25
27
20
7.25
27
30
Length
7.25
27
40
7.25
27
43*
7.25
27
50
* denotes baseline conditions
The 14 day maximum temperature and maximum temperature difference as calculated by
ConcreteWorks is shown in Table 6.6. The results show that an increase in the dimension of the
placement typically increases both the maximum temperature and maximum temperature
difference of the placement. However, there was no increase in either the maximum temperature
or maximum temperature for an increase in width over 27 feet. In addition, the length of the
placement had no effect on the temperature development of the placement.
74
Table 6.6. Dimensional size sensitivity study results
Maximum
Maximum
Temperature
Parameter Depth Width Length Temperature
Difference
Changed
(ft)
(ft)
(ft)
(°F)
(°F)
5
27
43
136
73
7.25*
27
43
147
92
Depth
10
27
43
154
108
15
27
43
162
124
20
27
43
166
131
7.25
10
43
144
65
7.25
20
43
147
89
Width
7.25
27*
43
147
92
7.25
30
43
147
92
7.25
40
43
147
92
7.25
27
20
147
92
7.25
27
30
147
92
Length
7.25
27
40
147
92
7.25
27
43*
147
92
7.25
27
50
147
92
*denotes baseline values
Dimensional Size
Given the width of the placement, larger than 27 feet, and the length, larger than 20 feet, is
excessively large in comparison to the depth of the placement, the element is not affected by an
increase in size. The results show that once a dimension reaches a length that is sufficiently
larger than the other dimension, there is no effect from increasing the dimension on either the
maximum temperature or maximum temperature difference in the placement. As the one
dimension increases, the thermal results converge and the dimension may be assumed to be
infinitely long. Typically, the depth of the placement is the smallest dimension and will have the
largest effect on the thermal development; the width and length of the placement will typically
play a lesser role in the thermal development of the placement.
6.2.3.2 Fresh Placement Temperature
The fresh placement temperature sensitivity study analyzed fresh placement temperatures that
are seen commonly in mass concrete construction. A temperature of 40°F was selected as a
minimum, which is the minimum temperature typically allowed by state agencies for general
construction. A maximum temperature of 90°F was selected to represent the maximum fresh
placement temperature, which is the maximum typically seen in general concrete construction.
The sensitivity study examined the effect of fresh placement temperature in ten-degree
increments from 40 to 90°F.
75
The maximum temperature and maximum temperature difference results for the range of fresh
placement temperatures, as analyzed by ConcreteWorks for the first 14 days after placement, are
shown in Table 6.7.
Table 6.7. Fresh placement temperature sensitivity study results
Fresh
Maximum
Placement
Temperature
Temperature
(°F)
(°F)
40
115
50
126
60
137
68.9*
147
70
148
80
159
90
170
* denotes baseline conditions
Maximum
Temperature
Difference (°F)
74
80
86
92
93
99
105
The results show that both the maximum temperature and maximum temperature difference
increase with an increase in the fresh placement temperature. For the increase in fresh placement
temperature from 40 to 90°F, the maximum temperature and maximum temperature difference
increase by 55°F and 31°F, respectively. For each degree increase in the fresh placement
temperature, the maximum temperature and maximum temperature difference increased on
average by 1.1°F and 0.62°F, respectively.
Fresh placement temperature directly affects the thermal development of a placement by
providing initial heat to the placement. In addition, the rate at which cement hydrates is affected
by the temperature of the concrete; the warmer the concrete is, the faster the process of
hydration. As the process of hydration is accelerated, heat is generated more rapidly, indirectly
increasing the maximum temperature of the placement. In addition, the increased hydration rate
generates larger thermal gradients, resulting from the limited ability of the concrete to dissipate
the generated heat in the placement to the surrounding environment.
6.2.3.3 Curing Method
The curing method sensitivity study considered five different curing methods used in mass
concrete construction: no curing method, white curing compound, black plastic, clear plastic, and
wet curing blanket. The results of the curing method sensitivity study are shown in Table 6.8,
providing the maximum temperature and the maximum temperature difference, as provided by
ConcreteWorks analysis.
76
Table 6.8. Curing method sensitivity study results
Curing Method
None*
White Curing Compound
Black Plastic
Clear Plastic
Wet Curing Blanket
* denotes baseline condition
Maximum
Temperature
(°F)
147
147
147
147
147
Maximum
Temperature
Difference (°F)
92
92
92
92
77
The results show that none of the five curing methods have an effect on the maximum
temperature of the placement. In addition, no curing method, white curing compound, black
plastic, and clear plastic had no effect on the maximum temperature difference of the placement.
Only the wet curing blanket had an effect on the thermal development, reducing the maximum
temperature difference by 15°F compared to the other curing methods.
The curing method had no effect on the rate of hydration of the concrete or the temperature of
the placement and, in turn, had little effect on the maximum temperature of the placement. No
curing method, white curing compound, black plastic, and clear plastic provide minimal, if any,
insulating value to the exterior surface of the concrete and, therefore, have no effect on the
maximum temperature difference of the placement.
The process of wet curing concrete provides additional insulation to the surface of the concrete,
resulting from both the blanket itself and the moisture on the surface concrete providing thermal
resistance to the surface of the placement. The combined thermal insulating properties of the
blanket and water provide a substantial reduction in the maximum temperature difference of the
placement.
6.2.3.4 Forming Method
The forming method sensitivity study considered the two most common formwork methods,
wood and steel, used in mass concrete construction. In addition, the study also considered the
effect of the color of steel formwork on the thermal development of mass concrete. The two
colors examined were red and yellow formwork.
The 14 day maximum temperature and maximum temperature difference analysis results for the
forming method sensitivity study are shown in Table 6.9.
77
Table 6.9. Forming method sensitivity study results
Formwork
Formwork
Material
Color
Natural Wood*
Natural Wood
Steel
Yellow
Steel
Red
* denotes baseline condition
Maximum
Temperature
(°F)
147
147
147
Maximum
Temperature
Difference (°F)
92
98
98
The results show that the formwork material and color had no effect on the maximum
temperature of a placement. In addition, steel formwork, both yellow- and red-colored, had an
increased maximum temperature difference compared to that of wood formwork. Wood
formwork had a maximum temperature difference 6°F less than that of steel formwork.
The reduced maximum temperature difference resulting from the use of the wood formwork is
largely the result of the thermal conductivity of wood compared to that of steel. Wood provides a
larger insulating value and resistance to heat flow compared to steel, retaining more heat at the
surface of the concrete, reducing the maximum temperature difference. The wood formwork
does not provide enough insulation to increase the maximum temperature compared to that of
steel formwork under these conditions.
6.2.3.5 Formwork Removal Time
The formwork removal time sensitivity study examined formwork removal times in the range of
48 hours to 336 hours in 24 hour increments. The minimum formwork removal time, 48 hours,
was chosen to represent the earliest practical time that formwork could be removed in mass
concrete construction. Typically for concrete elements subject to flexure (i.e., some surfaces
could be in tension) before 48 hours, the concrete does not have sufficient strength for the
formwork to be removed. The upper bound of the formwork removal time is 336 hours, or 14
days, which is the maximum allowable analysis time for ConcreteWorks.
The maximum temperature and maximum temperature difference results for the formwork
removal time sensitivity study are shown in Table 6.10.
78
Table 6.10. Formwork removal time sensitivity study results
Maximum
Maximum
Formwork
Removal Time Temperature Temperature
(°F)
Difference (°F)
(hr)
48
145
101
72
147
104
96
147
106
120
147
108
144
147
110
168
147
112
192
147
113
216
147
113
240
147
109
264
147
100
288
147
96
312*
147
92
336
147
77
* denotes baseline condition
The results show that the maximum temperature was not affected by the formwork removal time,
except for the 48 hour, which had a slightly reduced maximum temperature. The results show
that the maximum temperature difference was greatly affected by the formwork removal time.
For formwork removal times between 48 and 192 hours, the maximum temperature difference
increased with an increase in formwork removal time. In addition, the results show that for
formwork removal times of 216 to 336 hours, the maximum temperature difference decreased
with an increase in formwork removal time. The largest maximum temperature difference under
these conditions was during hours 192 and 216, with a maximum temperature difference of
113°F.
The results show that the formwork removal time has no effect on the maximum temperature of
the placement except for formwork removal times of 48 hours. Figure 6.1 shows that the
maximum temperature occurs around 85 hours after the element was placed for these conditions.
79
160
Temperature (°F)
140
120
ConcreteWorks
Maximum
Temperature
100
80
60
Average Ambient Air
Temperature
40
20
0
0
24 48 72 96 120 144 168 192 216 240 264 288 312 336
Time After Placement (hr)
Figure 6.1. ConcreteWorks maximum temperature development and average ambient air
temperature with time
If the formwork removal is to reduce the maximum temperature of the placement, it must be
removed before the maximum temperature in the placement occurs.
The results show that the formwork removal times of 192 and 216 hours result in the largest
maximum temperature difference. Figure 6.1 shows that for the conditions of this sensitivity
study, the ambient air temperature noticeably dropped starting at approximately 144 hours after
placement. The noticeable drop in the ambient air temperature largely accounts for the increased
maximum temperature difference between hours 144 and 216.
The formwork removal time had a lesser effect on the maximum temperature difference of the
placement in the time before 192 hours. Between the time of maximum temperature and 192
hours, the maximum temperature of the placement remains relatively constant and does not
noticeably change the maximum temperature difference of the placement.
As the formwork removal time for the placement is increased after 216 hours, the maximum
temperature difference of the placement decreases. This is the result of the placement being
allowed to cool gradually, shown by the decrease in the maximum temperature.
6.2.3.6 Subbase Material
The subbase sensitivity study considered the effect of various subbase materials on the thermal
development of mass concrete placements. The sensitivity study examined all subbase materials
available in ConcreteWorks to model mass concrete footings. The various subbase materials and
maximum temperature and maximum temperature difference as calculated by ConcreteWorks
are listed in Table 6.11.
80
Table 6.11. Subbase material sensitivity study results
Maximum
Maximum
Subbase
Temperature Temperature
Material
(°F)
Difference (°F)
Clay*
147
92
Granite
144
81
Limestone
145
84
Marble
144
80
Quartzite
143
72
Sandstone
145
82
Sand
151
105
Top Soil
147
91
Concrete
144
79
* denotes baseline condition
The results show that the maximum temperature and the maximum temperature difference are
both affected by the subbase material. Under the conditions of this sensitivity study, the
maximum temperature of the placement ranged from 143 to 151°F, and the maximum
temperature difference ranged from 72 to 105°F.
The difference in the thermal development is attributed to the thermal properties of the subbase
materials. The subbase material properties used by ConcreteWorks to model the placements are
listed in Table 6.12. ConcreteWorks does not use a standard set of thermal properties for
concrete subbase, assuming the same thermal properties as the concrete being analyzed.
Table 6.12. Subbase material thermal properties (Riding 2007)
Thermal
Specific
Subbase
Density Conductivity
Heat
3
Material (kg/m )
(W/m/K)
(J/kg/K)
Clay
1460
1.3
880
Granite
2630
2.79
775
Limestone
2320
2.15
810
Marble
2680
2.8
830
Quartzite
2640
5.38
1105
Sandstone
2150
2.9
745
Sand
1515
0.27
800
Top Soil
2050
0.52
1840
Concrete*
2254
2.77
837
* thermal properties are determined from the
concrete mix used in the sensitivity study
81
6
150
5
148
4
146
3
144
2
142
Sand
Top Soil
Clay*
Limestone
Sandstone
0
Concrete
138
Granite
1
Marble
140
Line shows Thermal Conductivity
(W/m/K)
152
Quartzite
Bars show Maximum Temperature (°F)
The results show that the thermal conductivity of the subbase has the largest effect on the
thermal development of the placement. Figure 6.2 shows the maximum temperature results of the
subbase sensitivity study with the corresponding thermal conductivity of each subbase. The
results show that, as the thermal conductivity decreases, the maximum temperature of the
placement increases.
Figure 6.2. Placement temperature versus subbase material thermal conductivity
6.2.3.7 Sensor Location
The sensor location sensitivity study was conducted to determine the effect of incorrect sensor
placement on the thermal readings. The sensitivity study looked at the three typical sensor
locations: center of the top surface, center of the side surface closest to the geometric center, and
geometric center of the placement. Each sensor location was examined to determine the effect of
varying levels of error on the thermal readings.
The sensitivity study was conducted by examining the thermal development data of the Pier 3
footing as analyzed by ConcreteWorks. ConcreteWorks provides thermal data for the center
cross section of the placement at five-minute time intervals for the entire duration of the thermal
analysis. The sensitivity study considered the cross section with the largest maximum
temperature difference, which occurred at hour 336. The data is represented by a contour plot in
Figure 6.3 to identify the general thermal gradient pattern of the placement.
82
0-20
40-60
80-100
120-140
20-40
60-80
100-120
140
120
80
60
40
Temperature (°F)
100
20
27.0
24.9
22.8
20.8
0
5.9
18.7
16.6
14.5
4.0
12.5
10.4 8.3
2.0
6.2
4.2
2.1
0.0
0.0
Figure 6.3. Pier 3 footing contour plot at time of maximum temperature difference
To examine the effects of incorrect sensor location, the cross-sectional thermal data were
analyzed in the width direction at the center line of the depth for the side surface sensor, center
line of the width in the depth direction for the top surface sensor, and center line of the width and
depth in the depth direction for the center sensor location. The locations and directions were
chosen to have the largest impact with regard to sensor location error. The location of the
thermal data utilized to evaluate the sensor location error is shown with the solid bold (red) lines
in Figure 6.4.
83
Figure 6.4. Top, side, and center sensor error locations
The baseline conditions for the top and side surface sensors were taken to be three inches in from
the outside surface at the corresponding center line. In addition, the baseline condition for the
center sensor is taken to be the intersection of the width and depth center lines. These locations
are typical in practice. It is assumed that if the sensors were placed at these locations, the thermal
reading errors would be zero.
To evaluate the changes from the baseline conditions, the thermal data from the surface to 15
inches below the surface were utilized to quantify the thermal gradient for the top and side
surface sensors. For the center sensor, 12 inches above and below the baseline condition was
utilized to quantify the thermal gradient for the center sensor. The discrete thermal data points,
falling in the respective ranges, were used to develop second-degree polynomial equations for
the thermal gradients at each sensor location. The graph of the thermal gradients for each sensor
is provided in Figure 6.5, with zero representing the baseline condition.
The graph represents sensor locations closer to the surface than the baseline condition as
negative numbers and locations closer to the center of the placement as positive numbers.
Negative temperature errors represent temperature readings larger than that of the baseline
conditions and positive temperature errors represent temperature readings smaller than the
baseline conditions.
84
40
Temperature Error (°F)
30
20
10
0
Top Suface
Sensor
Side Suface
Sensor
Center Sensor
-10
-20
-12
-8
-4
0
4
8
12
Sensor Placement Error (in)
Figure 6.5. Temperature errors for sensor placement errors
The results show that all of the investigated sensor locations are affected by the location. All
sensors show a decrease in the thermal reading temperature as the sensor location moves toward
the surface and an increase as the sensor location moves away from the surface of the placement.
The increase in the center temperature error with positive sensor placement error is the result of
the maximum temperature in the placement not occurring in the exact geometric center of the
placement. Due to the relatively large insulating value of the subbase compared to the top surface
insulation, the maximum temperature in the placement occurs slightly closer to the bottom of the
footing than the top.
The results show that the center sensor has the least amount of temperature error for a given
sensor placement error. In addition, the top surface sensor temperature error is the most affected
by a given error in sensor placement. Because the top surface sensor has the largest temperature
error for a given sensor placement error, a table is provided to characterize the temperature error
of the top surface sensor for a given sensor placement error. Table 6.13 shows how the
temperature varies below the surface, along with the temperature error, using a baseline of three
inches of concrete cover over the sensor.
85
Table 6.13. Top surface sensor temperature error by depth placement error
Actual
Depth
(in.)
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
Actual
Depth
Temperature
Error Temperature
Error
(°F)
(in.)
(°F)
-3
38.3
-11.3
-2
42.2
-7.5
-1
46.0
-3.7
0
49.7
0.0
1
53.2
3.6
2
56.7
7.1
3
60.1
10.5
4
63.4
13.8
5
66.6
17.0
6
69.7
20.1
7
72.7
23.1
8
75.6
26.0
9
78.4
28.8
10
81.2
31.5
11
83.8
34.1
12
86.3
36.6
The results show that substantial temperature reading errors may occur if precautions are not
taken to locate the sensors in the placement accurately. It is important to note that the maximum
temperature of the placement is not located generally at the exact geometric center of the
placement because of the difference in the boundary conditions between the top and bottom
surfaces of the placements, as shown by the temperature contour plot of Pier 3.
The greatly increased maximum temperature differences computed by ConcreteWorks compared
to actual conditions may be attributed largely to the sensor locations. ConcreteWorks computes
the maximum temperature difference from the absolute maximum and minimum temperature in
the placement. Actual temperature recordings are at discrete locations with a certain amount of
concrete cover and placement error.
From the cross-section data for the Pier 3 footing, accounting for only three sensor locations with
three inches of concrete cover without sensor placement error, the adjusted maximum
temperature difference would be 67.9°F. The adjusted maximum temperature difference, as
described above, is reduced greatly compared to that of the raw ConcreteWorks maximum
temperature difference of 92°F.
86
6.2.3.8 Ambient Air Temperature
The ambient air temperature sensitivity study examines the effect of the surrounding ambient air
temperature on the thermal development of mass concrete elements. The study examines the
ambient temperature of two different placement dates: October 30, 2008 and July 30, 2008.
These dates were selected to represent a warm ambient air temperature and a cool ambient air
temperature. A winter date was not selected to prevent complications of the concrete freezing.
October 30 represents a cool ambient air temperature, where freezing of the concrete is of little
concern. July 30 is one of the warmest times of the year typically in the Midwest and was
selected to represent the warmest ambient air temperature conditions.
In lieu of using the ConcreteWorks default values for the corresponding placement dates, the
actual historical weather data provided by the National Weather Service was input. This was
done to give a more accurate representation of how real weather conditions affect the thermal
development of mass concrete. The daily maximum and minimum temperatures for the day of
placement and the 14 subsequent days for each placement are listed in Table 6.14 as inputted
into ConcreteWorks.
Table 6.14. Ambient air temperature sensitivity study maximum and minimum
temperature inputs
Date
10/30/2008
10/31/2008
11/1/2008
11/2/2008
11/3/2008
11/4/2008
11/5/2008
11/6/2008
11/7/2008
11/8/2008
11/9/2008
11/10/2008
11/11/2008
11/12/2008
11/13/2008
Maximum Minimum
Maximum Minimum
(°F)
(°F)
Date
(°F)
(°F)
72
40
7/30/2011
90
69
70
39
7/31/2011
93
70
68
35
8/1/2011
91
71
76
48
8/2/2011
92
68
79
58
8/3/2011
101
77
74
57
8/4/2011
90
75
70
47
8/5/2011
84
67
49
36
8/6/2011
86
63
38
32
8/7/2011
89
61
34
28
8/8/2011
88
66
38
25
8/9/2011
85
68
36
26
8/10/2011
87
61
43
34
8/11/2011
84
67
39
34
8/12/2011
86
64
54
37
8/13/2011
93
66
The maximum temperature and maximum temperature difference as calculated by
ConcreteWorks for the two ambient air temperature conditions are shown in Table 6.15.
87
Table 6.15. Ambient air temperature sensitivity study results
Maximum
Maximum
Placement
Temperature Temperature
Date
(°F)
Difference (°F)
10/30/2008*
147
92
7/30/2008
150
68
* denotes baseline condition
The results show that the ambient air temperature has an effect on both the maximum
temperature and the maximum temperature difference of the placement. The warmer ambient air
temperature for July 30, 2008 generated a higher maximum temperature and a reduced maximum
temperature difference compared to that of the cooler ambient air temperature for October 30,
2008.
The ambient temperature and maximum temperature development with time, as calculated by
ConcreteWorks, is shown in Figure 6.6.
160
140
Temperature (°F)
120
7/30/08 Maximum
Temperature
100
10/30/08 Maximum
Temperature
80
60
7/30/08 Ambient
Temperature
40
10/30/08 Ambient
Temperature
20
0
0
24 48 72 96 120 144 168 192 216 240 264 288 312
Time After Placement (hr)
Figure 6.6. ConcreteWorks ambient air temperature and maximum temperature with time
after placement
The figure shows how ConcreteWorks approximates the ambient air temperature surrounding the
placement from the daily maximum and minimum temperautres. In addition, the graph shows
that the maximum temperature is reduced for the lower ambeint air temperature conditions for
October 30, 2008.
The maximum temperature and ambient air temperature curves show how the maximum
temperature difference changes for each ambient air condition. At the time of formwork removal,
312 hours after placement, the surface of the placement will cool to the ambient air temperature.
88
The maximum temperature difference will approach the difference of the maximum temperature
and the ambient air temperature.
The graph shows that, although the element placed on October 30, 2008 had a slightly reduced
maximum temperature, the ambeient air temperature is greatly reduced compared to that of the
placement poured on July 30, 2008. The greatly reduced ambient air temperature causes an
increase in the maximum temperature difference compared to the placement poured on July 30,
2008.
It is important to note that, in this study, only the ambient air temperature was varied. In actual
application, other parameters will also vary with the ambient air temperature including the fresh
placement temperature and soil temperature. The changes in the additional parameters will alter
the results in actual practice.
6.2.3.9 Cement Content
The cement content sensitivity study evaluated the effect of cement content in a concrete mix
proportion on the thermal development of mass concrete. The study analyzed cementitious
contents in increments of 100 lb/cy ranging from 527 to 827 lb/cy. Over the range of
cementitious content, the class F fly ash and GGBFS contents were held to the baseline
conditions of 105 and 207 lb/cy, respectively. The change in cementitious content only affected
the cement content as shown in Table 6.16.
Table 6.16. Cement content sensitivity study inputs
Total
Cementitious
Material (lb/cy)
427
527
627
727
827
Cement
Content
(lb/cy)
115
215
315
415
515
Class F
Fly Ash
(lb/cy)
105
105
105
105
105
GGBFS
(lb/cy)
207
207
207
207
207
The results of the cement content sensitivity study are shown in Table 6.17. The results show that
both the maximum temperature and the maximum temperature difference increased with an
increase in cement content. For this study, each additional 100lb/cy of cement increased the
maximum temperature and maximum temperature difference by approximately 9°F and 6°F,
respectively. Adding cement increases the heat in the placement due to the fact that additional
material is undergoing hydration. The additional heat generated in the placement results in an
increased maximum temperature and, subsequently, an increased maximum temperature
difference.
89
Table 6.17. Cement content sensitivity study results
Cementitious
Maximum
Content
Temperature
(lb/cy)
(°F)
527
136
627*
147
727
156
827
164
* denotes baseline condition
Maximum
Temperature
Difference
(°F)
85
92
98
103
6.2.3.10 Fly Ash Substitution
The fly ash substitution sensitivity study looked at the effect substituting class F and class C fly
ash for cement in a concrete mix proportion. The sensitivity study looked at the substitution of
fly ash in 10 percent increments from 0 to 50 percent of the total cementitious content. The upper
limit of 50 percent was set to represent typical mass concrete specifications. The total
cementitious content of 627 lb/cy was selected to following the previous baselines. Table 6.18
and Table 6.19 show the inputs used to complete the class F fly ash and class C fly ash
sensitivity study, respectively. No GGBFS was used in the mix proportion in an effort to
simplify the study.
Table 6.18. Class F fly ash sensitivity study inputs
Class F
Fly Ash
Cement
Substitution Content
(%)
(lb/cy)
0
627
10
564
20
502
30
439
40
376
50
314
Class F
Fly Ash
Content
(lb/cy)
0
63
125
188
251
313
90
Table 6.19. Class C fly ash sensitivity study inputs
Class C
Fly Ash
Cement
Substitution Content
(%)
(lb/cy)
0
627
10
564
20
502
30
439
40
376
50
314
Class C
Fly Ash
Content
(lb/cy)
0
63
125
188
251
313
Table 6.20 and Table 6.21 show the results of the sensitivity study for class F and C fly ash,
respectively. The results show that both the maximum temperature and maximum temperature
difference decreased with the substitution of class F fly ash. In addition, the substitution of class
C reduced the maximum temperature of the placement, and the maximum temperature difference
slightly.
Table 6.20. Class F fly ash sensitivity study results
Maximum
Class F
Maximum
Temperature
Fly Ash
Difference
Substitution Temperature
(°F)
(°F)
(%)
0
154
89
10
148
86
20
142
83
30
136
80
40
131
76
50
125
73
Table 6.21. Class C fly ash sensitivity study results
Maximum
Class C
Maximum
Temperature
Fly Ash
Temperature
Difference
Substitution
(°F)
(°F)
(%)
0
154
89
10
152
88
20
150
88
30
150
88
40
145
87
50
142
87
91
Both class F and C fly ash generate less heat during hydration compared to cement. The
chemical composition of class F fly ash allows for a larger reduction in the amount of heat
generated during hydration compared to class C fly ash, resulting from a lower CaO percentage.
Free lime content directly correlates to the amount of heat generated during hydration.
Class F fly ash substitution reduced the maximum temperature in the placement substantially as a
result of the chemical composition. The large reduction in the maximum temperature
subsequently led to a reduction in the maximum temperature difference. Class C fly ash
substitution only lowers the maximum temperature in the placement slightly, which correlates to
the minimal reduction in the maximum temperature difference.
6.2.3.11 GGBFS Substitution
The GGBFS sensitivity study explored the effect of the substitution of GGBFS on the thermal
development of mass concrete placements. The sensitivity study utilized a total cementitious
content of 627 lb/cy, following the previous baseline. The substitution percentage ranged from 0
to 50 percent in 10 percent increments. Table 6.22 identifies the inputs that were used to
complete the sensitivity study. No fly ash was used in the mix proportion in an effort to simplify
the study.
Table 6.22. GGBFS substitution sensitivity study inputs
GGBFS
Cement
Substitution Content
(%)
(lb/cy)
0
627
10
564
20
502
30
439
40
376
50
314
GGBFS
Content
(lb/cy)
0
63
125
188
251
313
Table 6.23 shows the maximum temperature and the maximum temperature difference as
calculated by ConcreteWorks for each GGBFS substitution percentage. The results show that
increasing the substitution of GGBFS has minimal effect on the maximum temperature of the
placement, and increases the maximum temperature difference of the placement slightly.
92
Table 6.23. GGBFS substitution sensitivity study results
GGBFS
Maximum
Maximum
Substitution Temperature Temperature
(%)
(°F)
Difference (°F)
0
154
89
10
154
91
20
154
93
30
154
95
40
156
98
50
158
101
GGBFS delays the generation of heat in concrete. The delayed heat generation causes the
maximum temperature in the placement to be reached at a later time compared to placements
without GGBFS. Since the heat is developed later, the concrete has less time to dissipate the heat
before the formwork is removed. Figure 6.7 shows that the placement with 50 percent GGBFS
substitution will be warmer at the time of form removal compared to the placement without
GGBFS, increasing the maximum temperature difference compared to the concrete without
GGBFS. However, the results of the GGBFS sensitivity study are in conflict with current
understanding of the effect of heat generation of concrete. It is generally believed that the
substitution of GGBFS for cement typically reduces the overall heat generation and subsequent
maximum temperature of mass concrete.
180
160
Temperature (°F)
140
120
0% - Maximum
Temperature
100
80
50% - Maximum
Temperature
60
0% - Maximum
Temperature Difference
40
50% - Maximum
Temperature Difference
20
0
0
24 48 72 96 120 144 168 192 216 240 264 288 312
Time After Placement (hr)
Figure 6.7. Maximum temperature and maximum temperature difference sensitivity study
results for 0% and 50% GGBFS substitution
93
6.2.3.12 Combined Class F Fly Ash and GGBFS Substitution
Class F fly ash and GGBFS are commonly combined in mix proportions used in mass concrete.
The sensitivity study looks at the thermal effect of the substitution of Class F fly ash and GGBFS
at different ratios and total cement substitution percentages. The study looked at class F fly ash
to GGBFS ratios from 0/100 for total cement substitution percentages ranging from 0 to 60
percent. The upper limit of 60 percent total cement substitution was selected to represent typical
mass concrete specifications.
The inputs for the cement, class F fly ash, and GGBFS content used to complete the sensitivity
study are shown in Table 6.24, Table 6.25, and Table 6.26, respectively. The tables are organized
with each column representing a different total cement substitution percentage. In addition, each
row identifies a class F fly ash to GGBFS percentage, with the percentage of the cement
substitution being fly ash in the left-most column and GGBFS in the right-most column.
Table 6.24. Combined class F fly ash and GGBFS substitution – cement content (lb/cy)
inputs
Fly Ash
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
0%
627
627
627
627
627
627
627
627
627
627
627
Total Cement Substitution
10% 20% 30% 40% 50% 60% GGBFS
564 502 439 376 314 251 100%
564 502 439 376 314 251 90%
564 502 439 376 314 251 80%
564 502 439 376 314 251 70%
564 502 439 376 314 251 60%
564 502 439 376 314 251 50%
564 502 439 376 314 251 40%
564 502 439 376 314 251 30%
564 502 439 376 314 251 20%
564 502 439 376 314 251 10%
564 502 439 376 314 251 0%
94
Table 6.25. Combined class F fly ash and GGBFS substitution – class F fly ash (lb/cy)
inputs
Fly Ash
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
Total Cement Substitution
0% 10% 20% 30% 40% 50% 60% GGBFS
0
0
0
0
0
0
0
100%
0
6
13
19
25
31
38 90%
0
13
25
38
50
63
75 80%
0
19
38
56
75
94
113 70%
0
25
50
75
100 125 150 60%
0
31
63
94
125 157 188 50%
0
38
75
113 150 188 226 40%
0
44
88
132 176 219 263 30%
0
50
100 150 201 251 301 20%
0
56
113 169 226 282 339 10%
0
63
125 188 251 314 376 0%
Table 6.26. Combined class F fly ash and GGBFS substitution – GGBFS (lb/cy) inputs
Fly Ash
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
Total Cement Substitution
0% 10% 20% 30% 40% 50% 60% GGBFS
0
63
125 188 251 314 376 100%
0
56
113 169 226 282 339 90%
0
50
100 150 201 251 301 80%
0
44
88
132 176 219 263 70%
0
38
75
113 150 188 226 60%
0
31
63
94
125 157 188 50%
0
25
50
75
100 125 150 40%
0
19
38
56
75
94
113 30%
0
13
25
38
50
63
75 20%
0
6
13
19
25
31
38 10%
0
0
0
0
0
0
0
0%
The results of the sensitivity study are shown in Table 6.27 and Table 6.28. The results are
organized in the same fashion as the inputs. Both the maximum temperature and the maximum
temperature difference follow the same trend; the largest temperature is for 60 percent total
cement substitution with 100 percent of the cement substitution being GGBFS. The minimum
value also occurs at 60 percent total cement substitution, with 100 percent of the substitution
being class F fly ash. Similar to the class F fly ash and GGBFS substitution sensitivity study,
class F fly ash reduces the maximum temperature and maximum temperature difference, while
GGBFS substitution increases both.
95
Table 6.27. Combined class F fly ash and GGBFS substitution results – maximum
temperature (°F)
Fly Ash
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
0%
154
154
154
154
154
154
154
154
154
154
154
Total Cement Substitution
10% 20% 30% 40% 50% 60% GGBFS
154 154 154 156 158 162 100%
153 153 153 153 155 158 90%
153 152 151 151 151 153 80%
152 150 149 148 148 149 70%
152 149 147 145 145 145 60%
151 148 145 143 141 140 50%
150 147 144 141 138 136 40%
150 146 142 138 135 132 30%
149 145 140 136 132 128 20%
149 143 138 133 128 124 10%
148 142 136 131 125 120 0%
Table 6.28. Combined class F fly ash and GGBFS substitution results – maximum
temperature difference (°F)
Fly Ash
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
Total Cement Substitution
0% 10% 20% 30% 40% 50% 60% GGBFS
89
91
93
95
98
101 106 100%
89
90
92
94
96
99
103 90%
89
90
91
92
94
96
99 80%
89
89
90
91
92
93
95 70%
89
89
89
89
89
90
91 60%
89
88
88
87
87
87
88 50%
89
88
87
86
85
85
84 40%
89
87
86
84
83
82
81 30%
89
87
85
83
81
79
77 20%
89
86
84
81
79
76
74 10%
89
86
83
80
76
73
70 0%
A graphic representation of the maximum temperature results is shown in Figure 6.8. In
accordance, the maximum temperature difference follows the same trend as that shown for the
maximum temperature.
96
Figure 6.8. Combined class F fly ash and GGBFS substitution maximum temperature
results
6.2.4 Discussion
The results of the sensitivity study show that all 12 of the parameters examined effect the thermal
development of typical Midwest border bridge mass concrete placements. The parameters that
have the largest effect on the maximum temperature, as shown by the results, include the depth
of the placement, fresh placement temperature, cementitious content, and class F fly ash
substitution.
In addition, parameters having the largest effect on the maximum temperature difference include
dimensional size, fresh placement temperature, ambient air temperature, cementitious content,
and class F fly ash substitution. The results also show that the location of the thermal sensors
plays a large role in maximum temperature and maximum temperature difference readings.
6.3 4C-Temp&Stress Sensitivity Study Results
The sensitivity study was conducted using the software program 4C-Temp&Stress and varying
construction, environmental, mix proportion, and thermal properties parameters as follows:
Construction Parameters
 Temperature sensor location
 Dimensional size
 Insulation method
 Form removal time
 Substructure material
 Cooling pipes
97
Environmental Parameters
 Fresh placement temperature
 Ambient temperature
Mix Proportion, Thermal Properties, and Others
 Cement content, fly ash, GGFBS
 Thermal conductivity
 Coefficient of thermal expansion
 Creep
 Coarse degree of meshes
The range for each set of parameters were selected in a manner that was similar to the one used
for ConcreteWorks. The summary of sensitivity analysis results are provided in Table 6.29.
The major findings can be summarized as follows:
 As sensor depth beneath the surface increases, the temperature increases.
 It is recommended that surface sensors be installed 3 inches below the concrete surface,
where the sensor could be easily attached to the steel rebar.
 Ethafoam, plast foam (10mm), foil with 5 mm air space, and plastic foil were calculated to
provide the lowest cracking risk in this analysis and are recommended to use as top
insulation.
 Formbord (25 mm), plywood, plywood formwork, and timber formwork, which were
calculated to provide the lowest cracking risk in this analysis are recommended for use as
side formwork.
 Maximum temperature and maximum temperature difference were found to increase with the
following:
o Increase of the least dimensional size
o Increase of fresh placement temperature during fall season weather (October)
o Decrease of form removal time
o Increase of cement content
 The use of supplementary cementitious materials, high thermal conductivity aggregate, and
low coefficient of expansion aggregate were effective in reducing the cracking potential.
 Cooling pipes were effective in reducing the maximum temperature and the thermal cracking
potential. The layout and numbers of cooling pipes were important in terms of reducing
cracking potential and construction cost.
 4C inputs could be adjusted to reflect changes in temperature sensor locations. Temperature
sensors near the surface are usually buried about 3 inches below the surface. The temperature
values for subsurface sensors are higher than what they would be for a sensor located on the
surface. This means that calculations directly using the temperature sensor data would
underestimate maximum temperature differences.
 To provide the best predictions using 4C, input methods that involve measured concrete
properties should be selected.
 It is recommended that users input changes of measured heat development and compressive
strength in 4C when mix design of concrete is changed.
98
Table 6.29. Parameters, ranges, and results considered in sensitivity study
Description
Detailed Items and Range
Tmax
∆Tmax
Max. σt/ft Ratio
Baseline
Soil
Footing #
Concrete
cement content
427, 527, 627, 727 pcy
175-284°F
60-90°F
1.1-3.3
Pier 3
F fly ash replacement
0%, 10%, 20%, 30%, 40% ,50%
175-120°F
60-40°F
1.1-0.6
Pier 3
C fly ash replacement
0%, 10%, 20%, 30%, 40% ,50%
175-150°F
60-45°F
1.1-0.75
Pier 3
Slag replacement
0%, 10%, 20%, 30%, 40% ,50%
175-160°F
60-100°F
1.1-1.1
Pier 3
Depth
1.4, 1.5, 1.8 ,2.1, 2.7 m
122-165°F
42-80°F
0.52-1.30
0.5-2.2
Pier 1
Structure Size
Width
3, 4.5, 6, 7.5, 9, 10.5 m
122°F
42-90°F
0.52-1.35
0.6
Pier 1
9, 12, 15, 18, 21 m
5.39, 8, 10,13,18 KJ/kg/°C
122°F
42°F
0.52
0.6
Pier 1
130-110°F
40-18°F
0.75-0.5
0.55-0.48
Pier 1
Concrete
properties
Length
Thermal conductivity
Thermal expansion
coefficient
122°F
42°F
0.52-1.1
0.5-1.3
Pier 1
Creep
w/ or w/o creep influence
45°F
0.75/3.5
Pier 3
72-42°F
1.5-0.75
Pier 3
40-50°F
0.75-1.55
Pier 3
35-80°F
0.75-1.1
Pier 3
Material
Form removal time
Formwork materials
Construction
Curing method
Cooling pipes
Fresh placement
Environmental temperature & placement
date & time
Others
7.36, 9, 11, 13 *10-6/°C,
156°F
48,72, 96, 120, 144, 168, 192, 216, 240, 264,
288, 312 hours
156°F
steel, plywood, plywood formwork, timber,
formbord (0.75, 1.0 in)
153-158°F
etha foam, foil with 5mm air space, plastic foil,
foam plastic,(0.4, 0.8, 1.2in), winter blanket
(2, 4in.)
153-158°F
w/ or w/o cpipes
156/130°F
40/20°F
0.81/0.75
Pier 3
summer: 40, 50, 60, 70, 80, 90°C
122-185°F
20-35°F
1.4-1.2
Pier 3
winter: 40,50,60,70,80,90 °C
118-176°F
32-53°F
0.75-1.5
Pier 3
Sensor locations
from surface to center of concrete with 3in
increment
Mesh sizes of finite
element analysis
2% (fine) or10% (coarse)
Substructure
soil or concrete
99
Pier 1
80-122°F
156/158°F
45-47°F
0.82-0.75
122°F
42°F
0.75
Pier 3
0.57
Pier 1
6.4 Discussion on Sensitivity Studies
Although both 4C and ConcreteWorks provide reasonable predictions of concrete thermal
behavior, there are some differences in the predictions. This was especially true for the
maximum temperature difference. ConcreteWorks predicts a higher temperature difference
consistently, because it compares the temperature at the surface with the temperature in the
middle of the placement. However, the temperature is usually not measured at the surface but
rather at the location of a temperature sensor, which was usually buried three or more inches in
the concrete. The surface temperature is influenced directly by the ambient temperature
conditions and thus a larger temperature difference is predicted.
Several forming and insulation alternatives can be selected in ConcreteWorks and the analysis in
4C using the same selections provided similar predictions. However, 4C provided more options
for forming and insulation materials. Furthermore, 4C provided results that were similar to those
of ConcreteWorks regarding the effect of changes in placement date. Generally, smaller
maximum temperature difference and less cracking potential were predicted for colder weather
placements in comparison to warmer weather placements. Issues with warmer weather placement
were mitigated when the fresh placement temperature was held to less than 70°F.
ConcreteWorks was developed to allow considering the influences of changes in mix design. The
results appear to be reasonable. Even though the 4C output confirmed the general trends
provided by ConcreteWorks, the maximum concrete temperatures were noticeably different. The
research team was not able to find a satisfactory method to input mix design parameters into 4C
to conduct a sensitivity analysis on mix design.
100
CHAPTER 7. TEMPERATURE DIFFERENCE CASE STUDIES
An objective of the present case study is to find the relationship between the maximum
temperature differences and the cracking potential of mass concrete. Field measurements are
often monitored by embedded temperature sensors and are often used to identify the maximum
temperature and maximum temperature differences of mass concrete elements.
7.1 I-80 Bridge
A total of 13 concrete structural elements, including the footings for Piers 1 through 6, the
columns for Piers 1 through 5, and the column for Pier 10 of the I-80 Bridge were analyzed using
the 4C program. Some of these elements had a soil subbase and some had a concrete subbase.
The maximum temperature difference and the бt/ft ratio of these concrete elements were obtained
from the analyses. Four different time intervals were considered: 0-24, 24-48, 48-72, and after 72
hours. A computer software application that performs statistical analyses, JMP 9 (JMP 9, 2012),
was used to analyze the data and to identify a relationship between the predicted maximum
temperature difference and the бt/ft ratio. The results are presented in Figure 7.1. Illustrated is a
linear relationship between the predicted maximum temperature difference and ln(бt/ft) for the
time interval investigated.
101
Figure 7.1. Relationship between бt/ft ratio and the maximum temperature difference
When the subbase is soil, the бt/ft ratios of concrete in footings or columns are very high during
first 24 hours (lower part of Figure 7.1). This may not be problematic because the concrete is
relatively soft and can deform without significant cracking before it fully sets and hardens. The
simulation or stress/strength prediction is often less accurate at such an early age because the
concrete properties are difficult to measure or assess accurately at an early age. Special attention
should be given to the high бt/ft ratios during the age of 24-48 hours. Figure 7.1 shows that
during the time from 24 to 48 hours, the бt/ft ratio reaches the critical value of 0.75 when the
concrete maximum temperature difference increases to approximately 32C. After 48 hours, the
concrete maximum temperature and temperature difference are reduced, obviously due to the
reduced heat of cement hydration. Therefore, the бt/ft ratio generally remains less than 0.75 in the
present analysis; this stress ratio is considered to represent a low cracking potential.
102
When a concrete member is placed on a concrete subbase, the upper part of Figure 7.1 shows
that the concrete elements generally have a low cracking potential (бt/ft <0.75) for the first72
hours. However, after 72 hours, the бt/ft ratio reaches the critical value of 0.75 when the concrete
maximum temperature difference increases to approximately 16 C. Furthermore, the бt/ft ratio
further increases as the maximum temperature difference increases in the concrete.
Coincidentally, formwork removal for the case study mass concrete construction projects
generally occurred after 72 hours or 3 days of placement. The highest temperature difference
often occurs shortly after the formwork removal. Therefore, the бt/ft ratios after formwork
removal are important for mass concrete placed on a concrete subbase, while the бt/ft ratios
before formwork removal are important for mass concrete placed on a soil subbase.
Based on the discussion above, in order to ensure that бt/ft <0.75, it is recommended that the
critical maximum temperature difference limits should be set at 30 °C for 24 to 48 hours after
concrete is placed when the subbase is soil and at 15 °C for after 72 hours when the subbase is
concrete. When the subbase material is soil, the allowable maximum temperature difference is
increasing during 0 to 72 hours. When the subbase material is concrete, the allowable maximum
temperature difference is decreasing. This may be due to the following:


A concrete subbase may provide more restraint to footings and columns in comparison to
soil, thus increasing the stresses in footings and columns with a concrete subbase with
increasing age
The data from 4C analyses are fitted using the covariance model for all of the various time
intervals that were analyzed, so that the R2 value of each model is the same
Further study is needed to fully explain the trends that were observed regarding the cracking
potential for mass concrete, especially for elements that have concrete subbases.
7.2 US 34 Bridge
In an effort to further investigate the applicability of the 4C program to river bridges in the US
Midwest, the Pier 4 footing of the US 34 Bridge project was analyzed using the 4C program. The
Pier 4 footing was constructed on a soil subbase on March, 30, 2012. The ambient temperature
and fresh placement temperature (15.6 °C) were monitored on-site. Cooling pipes were used for
this footing, and the temperature prediction results were compared with the collected field
measurements as shown in the top graph of Figure 7.2.
103
1
𝜎𝑡/𝑓𝑡 ratio
0.8
0.6
0.4
0.2
0
0
24
48
Time( hr)
72
96
Figure 7.2. Case study results for Pier 4 footing of US 34 Bridge
The maximum temperature of concrete had a 3% discrepancy between the predicted and actual
values. The prediction discrepancies for the temperature during the analysis period may be due to
the assumptions made in 4C analysis, such as input ambient temperature not being exactly the
same as actual monitored environmental temperature. The critical бt/ft ratio is below 0.75. This
matches with field observations that found the concrete element showed no evidence of thermal
cracking upon field investigation. These observations corroborate the finding from the study of
the I-80 Bridge that indicated the 4C program is useful in predicting the thermal behavior of
mass concrete for larger US Midwest river crossing bridges.
104
CHAPTER 8. CONCLUSIONS AND RECOMMENDATIONS
The research yielded the following conclusions and recommendations:
1. ConcreteWorks is capable of predicting the general trend of thermal development of mass
concrete elements. In a comparison between actual and predicted maximum temperatures for
22 different concrete elements on theI-80 WB Bridge, the errors ranged from underestimates
of 35°F to overestimates of about 1°F; the average was an underestimate of 12.3°F. In a
comparison between actual and predicted maximum temperature differences, errors ranged
from underestimates of 21°F to overestimates of 14°F with an average of 1.9°F. Some
adjustment to the inputs and outputs could be made to ensure that the results are conservative.
Input values would be easily available to Iowa DOT personnel. Output regarding cracking
potential is only available for the first seven days of the placement and cracking potential is
described qualitatively as low, medium, and high. Because of a programming limitation, the
entire analysis ends in 14 days, while thermal development continues on some typical
concrete placements in Iowa for a longer period.
2. 4C-Temp&Stress is also capable of predicting the general trend of thermal development of
mass concrete elements. A comparison between actual and predicted maximum concrete
temperatures for 26 concrete elements were within 25 degrees, except for stem elements,
which had predictions of lesser quality. Many input values would be easily available to Iowa
DOT personnel; however, some effort to correlate or calculate some input values is required.
The length of time for the output covers the entire thermal development period for the type of
construction in the case studies of I-80 WB and US 34. Output is provided as temperatures
and the stress ratio (tensile stress: tensile strength) at various locations. Iso-curves are also
available for temperature and stress ratio.
3. Sensitivity analysis using both Concrete Works and 4C both confirm actions that are
documented in the literature that are effective in controlling the thermal performance of mass
concrete elements. For example, reducing the fresh placement temperature, limiting cement
content, and substituting fly ash for concrete all tend to improve the thermal performance of
mass concrete. The sensitivity studies provide further verification regarding the operation of
ConcreteWorks and 4C-Temp&Stress.
4. The Iowa DOT maximum allowable temperature difference gradient limits specified in
Control Heat of Hydration DS-09047, August 17, 2010 are confirmed to be applicable for
bridges similar to that of the WB I-80 Missouri River Bridge and the US 34 Missouri River
Bridge, where bridge elements are founded on concrete. By having lower limits on the
maximum allowable temperature difference at earlier ages, the specification recognizes that
concrete is relatively weak shortly after placement and becomes stronger and more able to
resist thermal cracking as it matures.
5. Further investigation regarding the influence of subbase material on cracking and how to
model cooling pipes in mass concrete elements would be useful.
105
6. Enhancing ConcreteWorks to have longer analysis periods would increase its usefulness for
modeling mass concrete placements that are similar to those for the I-80 WB and US 34
bridges over the Missouri River.
7. The Iowa DOT could consider allowing contractors to have greater latitude in developing
plans for mass concrete placements if the potential success of such plans can be verified by
4C-Temp&Stress or ConcreteWorks.
106
REFERENCES
4C. 1998. User Manual 4C-Temp&Stress ver. 2.0 for Windows. DTI Building Technology.
AHTD. 2003. Standard specification for highway construction, Arkansas Highway and
Transportation Department, Little Rock, AR.
Ash Grove Cement Company. 2010. Type I/II cement Report, Ash Grove Cement Company,
Louisville, NE.
California DOT. 2010. Standard specifications, California Department of Transportation,
Sacramento, CA.
Carino, N. J., and Lew, H. S. 2001. The maturity method: From theory to application, National
Institute of Standards and Technology, Gaithersburg, MD.
Florida DOT. 2006. Structural design guidelines, Florida Department of Transportation,
Tallahassee, FL.
Florida DOT. 2010. Standard specifications for road and bridge construction, Florida Department
of Transportation, Tallahassee, FL.
Ge, Zhi. 2005. Predicting temperature and strength development of the fieild cocnrete. Ames,
Iowa, 2005.
Ge, Zhi, and Kejin Wang. 2003. Evaluating Properties of Blended Cements for Concrete
Pavements. The center for Portland Cment Concrete Pavement Technology, December
2003.
Headwaters Resources. 2005. Chemical comparison of fly ash and Portland cement, Headwaters
Resources, South Jordan, UT.
Idaho DOT. 2004. Standard specifications for highway construction, Idaho Transportation
Department, Boise, ID.
Illinois DOT. 2012. Illinois special provision 2012 - 1020.15 Heat of Hydration Control for
Concrete Structures, Illinois Department of Transportation, Springfield, IL.
Iowa DOT. 2010. DS-09047 Developmental specification for mass concrete – Control of heat of
hydration, Iowa Department of Transportation, Ames, IA.
Kentucky Transportation Cabinet. 2008. Special note for structural mass concrete, Kentucky
Transportation Cabinet, Frankfort, KY.
Kim, S. 2010. “Effect of heat generation from cement hydration on mass concrete placement.”
M.S. Thesis, Iowa State University, Ames, IA.
Kosmatka, S., Kerkhoff, B. and Panarese W. 2002. Design and control of concrete mixtures, 14th
Ed., Portland Cement Association, Skokie, IL.
New Jersey DOT. 2007. Standard specifications for road and bridge construction, New Jersey
Department of Transportation, Trenton, NJ.
New York State DOT. 2012. Concrete for structures class MP (mass placement), New York
State Department of Transportation, Albany, NY.
Rhode Island DOT. 2010. Standard specifications for road and bridge construction, Rhode Island
Department of Transportation, Providence, RI.
Riding, K. 2007. “Early age concrete thermal stress measurement and modeling.” Ph.D
Dissertation, The University of Texas at Austin, Austin, TX.
South Carolina DOT. 2007. Standard specifications for highway construction, South Carolina
Department of Transportation, Columbia, SC.
Texas DOT. 2004. Standard specifications for construction and maintenance of highways,
streets, and bridges, Texas Department of Transportation, Austin, TX.
Wang, K., Hu, J., and Ge, Z. 2008. Task 6: Material Thermal Input for Iowa Materials. Center of
Transportation Research and Education, Iowa State University, Ames, IA. February
2008.
West Virginia DOT. 2006. Special provision for section 601 – Structural, West Virginia
Department of Transportation Division of Highways, Charleston, WV.
Westman, Gustaf. 1999. Concrete Creep and Thermal Stresses. Sweden: Division of Structural
Engineering, Lulea University of Technology, 1999.
APPENDIX A. INSTALLATION AND LAYOUT OF THERMAL SENSORS
Figure A.1. Installation of thermal sensors with cable ties and tie wire
109
Figure A.2. Top surface and center sensors installed with electrical tape
110
Figure A.3. Thermal sensor supported and protected with supplemental rebar
111
Figure A.4. Typical top surface and center sensor layout
112
Figure A.5. Typical side surface and center sensor layout
113
Figure A.6. Verification of proper sensor function after installation
114
APPENDIX B. COMPARISON BETWEEN 4C (PREDICTION) AND CTL (ACTUAL)
160
140
Temp( F)
120
100
4C
80
CTL
60
40
20
0
0
50
100
time(hrs)
150
200
Figure B.1. Maximum temperature development for Pier 2 footing comparison between
measured (CTL) and predicted (4C)
160
140
Temp (F)
120
100
80
4C
60
CTL
40
20
0
0
50
100
time(hr)
150
200
Figure B.2. Maximum temperature development for Pier 3 footing comparison between
measured (CTL) and predicted (4C)
115
160
140
Temp(F)
120
100
80
4C
60
CTL
40
20
0
0
50
100
time(hr)
150
200
Figure B.3. Maximum temperature development for Pier 4 footing comparison between
measured (CTL) and predicted (4C)
160
140
Temp (F)
120
100
80
4C
60
CTL
40
20
0
0
50
100
Time(hr)
150
200
Figure B.4. Maximum temperature development for Pier 5 footing comparison between
measured (CTL) and predicted (4C)
116
160
140
Temp (F)
120
100
80
4c
60
CTL
40
20
0
0
50
100
150
200
Time(hr)
Figure B.5. Maximum temperature development for Pier 6 footing comparison between
measured (CTL) and predicted (4C)
160
140
Temp (F)
120
100
80
4C
60
CTL
40
20
0
0
50
100
150
200
Time(hr)
Figure B.6. Maximum temperature development for Pier 1 stem comparison between
measured (CTL) and predicted (4C)
117
160
140
Temp (F)
120
100
80
4C
60
CTL
40
20
0
0
50
100
Time(hr)
150
200
Figure B.7. Maximum temperature development for Pier 2 stem comparison between
measured (CTL) and predicted (4C)
160
140
Temp(F)
120
100
4C
80
CTL
60
40
20
0
0
50
100
Time(hr)
150
200
Figure B.8. Maximum temperature development for Pier 3 stem comparison between
measured (CTL) and predicted (4C)
118
160
140
Temp(F)
120
100
4C
80
CTL
60
40
20
0
0
50
100
Time(hr)
150
200
Figure B.9. Maximum temperature development for Pier 4 stem comparison between
measured (CTL) and predicted (4C)
160
140
Temp(F)
120
100
80
4C
60
CTL
40
20
0
0
50
100
Time(hr)
150
200
Figure B.10. Maximum temperature development for Pier 5 stem comparison between
measured (CTL) and predicted (4C)
119
160
140
Temp. (F)
120
100
4C
80
CTL
60
40
20
0
0
50
100
Time(hr)
150
200
Figure B.11. Maximum temperature development for Pier 7 stem comparison between
measured (CTL) and predicted (4C)
160
140
Temp (F)
120
100
4C
80
CTL
60
40
20
0
0
50
100
Time(hr)
150
200
Figure B.12. Maximum temperature development for Pier 9 stem comparison between
measured (CTL) and predicted (4C)
120
160
140
Temp(F)
120
100
80
4C
60
CTL
40
20
0
0
50
100
150
200
Time(hr)
Figure B.13. Maximum temperature development for Pier 1 cap comparison between
measured (CTL) and predicted (4C)
160
140
Temp(F)
120
100
4C
80
CTL
60
40
20
0
0
50
100
Time(hr)
150
200
Figure B.14. Maximum temperature development for Pier 2 cap comparison between
measured (CTL) and predicted (4C)
121
160
140
Temp(F)
120
100
4C
80
CTL
60
40
20
0
0
50
100
Time(hr)
150
200
Figure B.15. Maximum temperature development for Pier 3 cap comparison between
measured (CTL) and predicted (4C)
160
140
Temp(F)
120
100
4C
80
CTL
60
40
20
0
0
50
100
Time(hr)
150
200
Figure B.16. Maximum temperature development for Pier 4 cap comparison between
measured (CTL) and predicted (4C)
122
160
140
Temp(F)
120
100
4C
80
CTL
60
40
20
0
0
50
100
Time(hr)
150
200
Figure B.17. Maximum temperature development for Pier 5 cap comparison between
measured (CTL) and predicted (4C)
160
140
Temp(F)
120
100
80
4C
60
CTL
40
20
0
0
50
100
Time(hr)
150
200
Figure B.18. Maximum temperature development for Pier 1 column comparison between
measured (CTL) and predicted (4C)
123
160
140
Temp.(F)
120
100
4C
80
CTL
60
40
20
0
0
50
100
Time(hr)
150
200
Figure B.19. Maximum temperature development for Pier 2 column comparison between
measured (CTL) and predicted (4C)
160
140
Temp(F)
120
100
4C
80
CTL
60
40
20
0
0
50
100
Time(hr)
150
200
Figure B.20. Maximum temperature development for Pier 3 column comparison between
measured (CTL) and predicted (4C)
124
160
140
Temp(F)
120
100
80
4C
60
CTL
40
20
0
0
50
100
150
200
Time(hr)
Figure B.21. Maximum temperature development for Pier 4 column comparison between
measured (CTL) and predicted (4C)
160
140
Temp(F)
120
100
80
4C
60
CTL
40
20
0
0
50
100
150
200
Time(hr)
Figure B.22. Maximum temperature development for Pier 2 column comparison between
measured (CTL) and predicted (4C)
125
160
140
Temp(F)
120
100
80
4C
60
CTL
40
20
0
0
50
100
150
200
Time(hr)
Figure B.23. Maximum temperature development for Pier 7 column comparison between
measured (CTL) and predicted (4C)
180
160
140
Temp(F)
120
100
4C
80
CTL
60
40
20
0
0
50
100
Time(hr)
150
200
Figure B.24. Maximum temperature development for Pier 10 column comparison between
measured (CTL) and predicted (4C)
126
APPENDIX C. CONCRETEWORKS WESTBOUND I-80 CASE STUDY THERMAL
RESULTS
140
130
Temperature (°F)
120
110
Actual Center
100
CW Center
90
Actual Top
CW Top
80
Actual Side
70
CW Side
60
50
0
24
48
72
96
120
144
168
192
Time after placement (hours)
Figure C.1. WB I-80 case study thermal results – Pier 1 footing
100
Temperature (°F)
90
Actual Center
80
CW Center
Actual Top
70
CW Top
Actual Side
60
CW Side
50
0
24
48
72
Time after placement (hours)
Figure C.2. WB I-80 case study thermal results – Pier 1 stem/column
127
110
100
Temperature (°F)
90
Actual Center
80
CW Center
Actual Top
70
CW Top
Actual Side
60
CW Side
50
40
0
24
48
72
Time after placement (°F)
Figure C.3. WB I-80 case study thermal results – Pier 1 cap
140
130
Temperature (°F)
120
Actual Center
110
CW Center
100
Actual Top
90
CW Top
Actual Side
80
CW Side
70
60
0
24
48
72
96
120 144 168 192 216 240 264
Time after placement (hours)
Figure C.4. WB I-80 case study thermal results – Pier 2 footing
128
140
130
120
Temperature (°F)
110
Actual Center
100
90
CW Center
80
Actual Top
70
CW Top
60
Actual Side
50
CW Side
40
30
0
24
48
72
96
120
144
168
192
216
Time after placement (hours)
Figure C.5. WB I-80 case study thermal results – Pier 2 stem
130
120
Temperature (°F)
110
Actual Center
100
CW Center
Actual Top
90
CW Top
80
Actual Side
CW Side
70
60
0
24
48
72
96
Time after placement (hours)
Figure C.6. WB I-80 case study thermal results – Pier 2 column
129
140
130
Temperature (°F)
120
110
Actual Center
100
CW Center
90
Actual Top
CW Top
80
Actual Side
70
CW Side
60
50
0
24
48
72
96
120
Time after placement (hours)
Figure C.7. WB I-80 case study thermal results – Pier 2 cap
160
150
140
Temperature (°F)
130
120
Actual Center
110
CW Center
100
Actual Top
90
CW Top
80
Actual Side
70
CW Side
60
50
0 24 48 72 96 120 144 168 192 216 240 264 288 312 336 360
Time after placement (hours)
Figure C.8. WB I-80 case study thermal results – Pier 3 footing
130
140
130
Temperature (°F)
120
110
Actual Center
100
CW Center
90
Actual Top
CW Top
80
Actual Side
70
CW Side
60
50
0
24
48
72
96
120 144 168 192 216 240 264
Time after placement (hours)
Figure C.9. WB I-80 case study thermal results – Pier 3 stem
130
120
Temperature (°F)
110
Actual Center
100
CW Center
90
Actual Top
80
CW Top
Actual Side
70
CW Side
60
50
0
24
48
72
96
120
144
Time after placement (hours)
Figure C.10. WB I-80 case study thermal results – Pier 3 column
131
150
140
Temperature (°F)
130
120
Actual Center
110
CW Center
100
Actual Top
CW Top
90
Actual Side
80
CW Side
70
60
0
24
48
72
96
120
144
Time after placement (hours)
Figure C.11. WB I-80 case study thermal results – Pier 3 cap
150
140
Temperature (°F)
130
120
Actual Center
110
CW Center
100
Actual Top
CW Top
90
Actual Side
80
CW Side
70
60
0
24
48
72
96
120
144
168
Time after placement (hours)
*side sensor was not turned on until hours 16
Figure C.12. WB I-80 case study thermal results – Pier 4 footing
132
140
130
120
Temperature (°F)
110
100
Actual Center
90
CW Center
80
Actual Top
70
CW Top
60
Actual Side
50
CW Side
40
30
20
0
24
48
72
96 120 144 168 192 216 240 264 288 312
Time after placement (hours)
Figure C.13. WB I-80 case study thermal results – Pier 4 stem
150
140
130
Temperature (°F)
120
110
Actual Center
100
CW Center
90
Actual Top
80
CW Top
70
Actual Side
60
CW Side
50
40
0
24
48
72
96
120
Time after placement (hours)
Figure C.14. WB I-80 case study thermal results – Pier 4 column
133
130
120
Temperature (°F)
110
Actual Center
100
CW Center
90
Actual Top
80
CW Top
Actual Side
70
CW Side
60
50
0
24
48
72
96
120
Time after placement (hours)
Figure C.15. WB I-80 case study thermal results – Pier 4 cap
140
130
120
Temperature (°F)
110
Actual Center
100
90
CW Center
80
Actual Top
70
CW Top
60
Actual Side
50
CW Side
40
30
0
24 48 72 96 120 144 168 192 216 240 264 288 312 336
Time after placement (hours)
Figure C.16. WB I-80 case study thermal results – Pier 5 footing
134
150
140
130
Temperature (°F)
120
110
Actual Center
100
CW Center
90
Actual Top
80
CW Top
70
Actual Side
60
CW Side
50
40
30
0
24
48
72
96 120 144 168 192 216 240 264 288
Time after placement (hours)
Figure C.17. WB I-80 case study thermal results – Pier 5 stem
150
140
130
Temperature (°F)
120
110
Actual Center
100
CW Center
90
Actual Top
80
CW Top
70
Actual Side
60
CW Side
50
40
0
24
48
72
96
120
144
Time after placement (hours)
Figure C.18. WB I-80 case study thermal results – Pier 5 column
135
150
140
Temperature (°F)
130
120
Actual Center
110
CW Center
100
Actual Top
CW Top
90
Actual Side
80
CW Side
70
60
0
24
48
72
96
120
144
Time after placement (hours)
Figure C.19. WB I-80 case study thermal results – Pier 5 cap
160
150
140
Temperature (°F)
130
120
Actual Center
110
CW Center
100
Actual Top
90
CW Top
80
Actual Side
70
CW Side
60
50
40
0 24 48 72 96 120 144 168 192 216 240 264 288 312 336 360
Time after placement (hours)
Figure C.20. WB I-80 case study thermal results – Pier 6 footing
136
160
150
140
Temperature (°F)
130
120
110
Actual Center
100
CW Center
90
Actual Top
80
CW Top
70
Actual Side
60
CW Side
50
40
30
0
24 48 72 96 120 144 168 192 216 240 264 288 312 336
Time after placement (hours)
Figure C.21. WB I-80 case study thermal results – Pier 6 column
137
APPENDIX D. US 34 CASE STUDY THERMAL RESULTS
130
120
Temperature (°F)
110
100
Actual Center
90
CW Center
80
Actual Top
70
CW Top
60
Actual Side
50
CW Side
40
30
0
24
48
72
96
120
144
Time after placement (hours)
Figure D.1. US 34 case study thermal results – Pier 2 footing – A
130
120
Temperature (°F)
110
100
Actual Center
90
CW Center
80
Actual Top
70
CW Top
60
Actual Side
50
CW Side
40
30
0
24
48
72
96
120
144
Time after placement (hours)
Figure D.2. US 34 case study thermal results – Pier 2 footing – B
138
130
120
Temperature (°F)
110
100
Actual Center
90
CW Center
80
Actual Top
CW Top
70
Actual Side
60
CW Side
50
40
0
24
48
72
96
120
144
168
Time after placement (hours)
Figure D.3. US 34 case study thermal results – Pier 2 footing – C
130
120
Temperature (°F)
110
100
Actual Center
90
CW Center
80
Actual Top
CW Top
70
Actual Side
60
CW Side
50
40
0
24
48
72
96
120
144
168
192
216
Time after placement (hours)
Figure D.4. US 34 case study thermal results – Pier 2 footing – D
139
140
130
Temperature (°F)
120
110
Actual Center
100
CW Center
90
Actual Side
CW Side
80
70
60
0
24
48
72
96
120
Time after placement (hours)
Figure D.5. US 34 case study thermal results – Pier 2 column – A
140
130
Temperature (°F)
120
110
Actual Center
100
CW Center
90
Actual Side
CW Side
80
70
60
0
24
48
72
96
120
Time after placement (hours)
Figure D.6. US 34 case study thermal results – Pier 2 column – B
140
130
120
Temperature (°F)
110
100
Actual Center
90
CW Center
80
Actual Side
CW Side
70
60
50
0
24
48
72
96
Time after placement (hours)
Figure D.7. US 34 case study thermal results – Pier 2 column – C
140
130
Temperature (°F)
120
110
100
Actual Center
CW Center
90
Actual Side
80
CW Side
70
60
50
0
24
48
72
96
120
144
Time after placement (hours)
Figure D.8. US 34 case study thermal results – Pier 2 column – D
141
140
130
Temperature (°F)
120
110
Actual Center
100
CW Center
90
Actual Top
CW Top
80
Actual Side
70
CW Side
60
50
0
24
48
72
96
120
Time after placement (hours)
Figure D.9. US 34 case study thermal results – Pier 2 cap
150
140
Temperature (°F)
130
120
Actual Center
110
CW Center
100
Actual Top
CW Top
90
Actual Side
80
CW Side
70
60
0
24
48
72
96
120
144
168
192
Time after placement (hours)
Figure D.10. US 34 case study thermal results – Pier 3 footing – C
142
150
140
Temperature (°F)
130
120
Actual Center
110
CW Center
100
Actual Top
CW Top
90
Actual Side
80
CW Side
70
60
0
24
48
72
96
120
144
168
192
Time after placement (hours)
Figure D.11. US 34 case study thermal results – Pier 3 footing – D
150
140
Temperature (°F)
130
120
110
Actual Center
100
CW Center
90
Actual Side
80
CW Side
70
60
50
0
24
48
72
Time after placement (hours)
Figure D.12. US 34 case study thermal results – Pier 3 column – A
143
150
140
Temperature (°F)
130
120
110
Actual Center
100
CW Center
90
Actual Side
80
CW Side
70
60
50
0
24
48
72
Time after placement (hours)
Figure D.13. US 34 case study thermal results – Pier 3 column – B
150
140
Temperature (°F)
130
120
110
Actual Center
100
CW Center
Actual Side
90
CW Side
80
70
60
0
24
48
72
96
Time after placement (hours)
Figure D.14. US 34 case study thermal results – Pier 3 column – C
144
160
150
Temperature (°F)
140
130
120
Actual Center
110
CW Center
100
Actual Side
90
CW Side
80
70
60
0
24
48
72
96
Time after placement (hours)
Figure D.15. US 34 case study thermal results – Pier 3 column – D
145
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