Prediction Model For Concrete Behavior: Final Report
1. Report No.FHWA/TX-08/0-4563-1Technical Report Documentation Page2. Government3. Recipient’s Catalog No.Accession No.4. Title and SubtitlePrediction Model for Concrete Behavior—Final Report5. Report DateOctober 2007, Rev. May 20086. Performing Organization Code7. Author(s)8. Performing Organization Report No.Kevin J. Folliard, Maria Juenger, Anton Schindler, Kyle0-4563-1Riding, Jonathan Poole, Loukas F. Kallivokas, SamuelSlatnick, Jared Whigham, J.L. Meadows9. Performing Organization Name and Address10. Work Unit No. (TRAIS)Center for Transportation Research11. Contract or Grant No.The University of Texas at Austin0-45633208 Red River, Suite 200Austin, TX 78705-265012. Sponsoring Agency Name and Address13. Type of Report and Period CoveredTexas Department of TransportationTechnical ReportResearch and Technology Implementation OfficeSeptember 2002- August 2007P.O. Box 5080Austin, TX 78763-508014. Sponsoring Agency Code15. Supplementary NotesProject performed in cooperation with the Texas Department of Transportation and the Federal HighwayAdministration.16. AbstractThis report summarizes work performed under Texas Department of Transportation (TxDOT) Project4563, Prediction Model for Concrete Behavior. The main product developed under this project is a softwareprogram, named Concrete Works, which gives laboratory technicians, engineers, and contractors a tool thatcombines concrete design, analysis, and performance prediction to improve and optimize the performance ofconcrete structures.A unique feature of the testing performed is the use of rigid cracking frames. This test was developed inGermany, and measures the cracking sensitivity of a restrained dog-bone-shaped concrete specimen from thetime of concrete placement. Temperature-controlled formwork is used to cure the specimen to match fieldconditions of mass concrete members. These frames are designed to allow fresh concrete to be cast into theirformwork, which enables the study of very early-age behavior of concrete mixtures. More than 70 tests havebeen completed to date and these results were used to characterize the very early-age creep behavior and risk ofcracking of various concretes. Mixture-specific heat of hydration values are used to accurately model the effectof various cementitious materials material on the in-place concrete temperature distribution. The model hasbeen calibrated with over 33,000 hours of temperature data collected from field sites. The software providesdetailed results to check compliance with specification to control thermal cracking, alkali silica reaction,delayed ettringite formation, and service-life expectancy.This report concludes with a section aimed at implementing ConcreteWorks, with emphasis on how bestto use, specify, and check compliance with mass concrete design guidelines.17. Key Words18. Distribution Statementprediction model, concrete, concreteworksNo restrictions. This document is available to thepublic through the National Technical InformationService, Springfield, Virginia 22161; www.ntis.gov.19. Security Classif. (of report) 20. Security Classif. (of this page) 21. No. of pagesUnclassifiedUnclassified78Form DOT F 1700.7 (8-72) Reproduction of completed page authorized22. Price
Prediction Model for Concrete Behavior—Final ReportKevin J. FolliardMaria JuengerAnton SchindlerKyle RidingJonathan PooleLoukas F. KallivokasSamuel SlatnickJared WhighamJ.L. MeadowsCTR Technical Report:Report Date:Research Project:Research Project Title:Sponsoring Agency:Performing Agency:0-4563-1October 2007, Rev. May 20080-4563Prediction Model for Concrete BehaviorTexas Department of TransportationCenter for Transportation Research at The University of Texas at AustinProject performed in cooperation with the Texas Department of Transportation and the Federal HighwayAdministration.
Center for Transportation ResearchThe University of Texas at Austin3208 Red RiverAustin, TX 78705www.utexas.edu/research/ctrCopyright 2008Center for Transportation ResearchThe University of Texas at AustinAll rights reservedPrinted in the United States of America
DisclaimersAuthors’ Disclaimer: The contents of this report reflect the views of the authors, who areresponsible for the facts and the accuracy of the data presented herein. The contents do notnecessarily reflect the official view or policies of the Federal Highway Administration or theTexas Department of Transportation. This report does not constitute a standard, specification, orregulation.Patent Disclaimer: There was no invention or discovery conceived or first actuallyreduced to practice in the course of or under this contract, including any art, method, process,machine manufacture, design or composition of matter, or any new useful improvement thereof,or any variety of plant, which is or may be patentable under the patent laws of the United Statesof America or any foreign country.Engineering DisclaimerNOT INTENDED FOR CONSTRUCTION, BIDDING, OR PERMIT PURPOSES.Project Engineer: David W. FowlerProfessional Engineer License Number: Texas No. 27859P. E. Designation: Researcherv
AcknowledgmentsThe authors express appreciation to the TxDOT Project Director (Ralph Browne), membersof the Project Monitoring Committee, and the staff at the Concrete Durability Center.vi
Table of Contents1. Introduction .11.1Thermal Cracking .11.2 Durability Problems.32. Heat of Hydration .72.1Introduction .72.2Method for Calculating the Apparent Activation Energy .72.3Ea Trends .92.4Model for Estimating Activation Energy .122.5Semi-Adiabatic Testing .132.6Calculation of Adiabatic Temperature Rise .132.7Hydration Trends .162.8 Model for the Hydration of Cementitious Systems .183. Temperature Modeling .213.1Basics of Temperature Prediction .213.2Concrete Member Models .243.3 Comparison with Field Site Data .274. Development of Early-age Properties .314.2Mechanical Property Development .334.3Free Shrinkage Device .354.4Cracking Frame Methodology .364.5Creep Stresses .384.6Coefficient of Thermal Expansion (CTE) Testing .404.7Cracking Frame Results .404.8Limitations .414.9 Autogenous Shrinkage.425. ConcreteWorks .435.2General Inputs .445.3Member Geometry.455.4Mixture Design .465.5Material/Mechanical Properties.475.6Construction Inputs .485.7Input Check .49vii
5.8 Results .496. Project Implementation .536.1Technology Transfer .536.2Training .536.3Trial Software Use .536.4Public Dissemination of Research .546.5Specification Changes .546.6 User Feedback .597. Conclusions .617.1Summary.617.2Economic Benefits.617.3 Additional Research .62References .63viii
List of FiguresFigure 1.1 Thermal Cracking in a column in the IH-10 in Houston, TX (photo courtesy ofJ.C. Liu) .2Figure 1.2 DEF in a column in San Antonio, TX .4Figure 1.3 ASR in a transmission tower foundation in La Grange, TX .5Figure 2.1 Effect of Increasing αu on the Hydration Curve .13Figure 2.2 Effect of Increasing τ on the Hydration Curve .14Figure 2.3 Effect of Increasing β on the Hydration Curve .14Figure 2.4 Isothermal Calorimeter (Left) and Semi-Adiabatic Calorimeter with ConcreteSample (Right) .15Figure 3.1 Control Volume Example - Three Neighboring Nodes (Riding 2007) .22Figure 3.2 Summary of Column Boundary Conditions (Riding 2007) .24Figure 3.3 Simplified Rectangular Column Model used in ConcreteWorks (Riding 2007) .25Figure 3.4 Example Rectangular Column Node and Control Volumes (Riding 2007) .26Figure 3.5 Rectangular Column during Form Removal and the Beginning of the Secondconstruction stage (Riding 2007) .27Figure 4.1 Flow chart describing the relationship between different parameters in thermalstress modeling of concrete structures (Riding 2007).32Figure 4.2 Free Shrinkage Frame a) Diagram and b) Frame used for this project .36Figure 4.3 Rigid Cracking Frame Drawing .37Figure 4.4 Photograph of Rigid Cracking Frame (Whigham 2005) .38Figure 5.2 “General Inputs” Screen (Riding 2007) .45Figure 5.3 “Mixture Proportion Inputs” Screen (Riding 2007) .46Figure 5.4 “Construction Inputs” Screen for a Rectangular Column (Riding 2007) .48Figure 5.5 “Mix Checks” Tab for a Rectangular Column (Riding 2007) .50Figure 5.6 Cracking Risk Classification Chart (Riding 2007) .51Figure 5.7 “Animation” Tab for a Rectangular Column (Riding 2007) .52Figure 6.1 Temperature sensor locations for a rectangular column.56Figure 6.2 Temperature sensor placement for a rectangular column with insulation or aform liner on the longer of the two plan dimensions .57Figure 6.3 Temperature Difference Modification Factor Chart for a Rectangular Column .58Figure 6.4 Maximum temperature Difference Versus the in-place Concrete CompressiveStrength for Different Temperature Difference Modification Factors .58ix
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List of TablesTable 2.1 Summary of Variables that affect Ea (Poole 2007) .11Table 2.2 Effect of Different Mixture Characteristics on Exponential Model HydrationParameters .18Table 3.1 Comparison of Predicted to Measured Maximum Concrete MemberTemperature .28Table 3.2 Comparison of Predicted to Measured Maximum Concrete TemperatureDifference .28Table 4.1 Effects of MLLM Parameters on Concrete Stress Relaxation (Riding 2007) .41Table 5.1 Software features available for each concrete member type (Riding 2007) .43Table 6.1 Proposed Maximum in-Place Temperature Limit Specification .55xi
1. IntroductionThe cost of repairing or replacing bridges that are not functionally obsolete is staggering.The premature deterioration of our infrastructure from cracking and concrete material relateddurability problems can be prevented. To ensure a long service life for a concrete structure it iscritical to plan appropriately during the design phase and to take appropriate precautions duringthe construction phase. Consideration of the causes of concrete deterioration during constructionplanning can ensure a maximum use of locally available, cost effective materials, improveconstruction efficiency and speed, and ensure a durable structure.In order for engineers and contractors to consider concrete durability in the design andconstruction planning stages, these professionals need to understand the issues affecting astructure’s service life. They also need a simple, user-friendly method or tool that will allowthem to quickly evaluate the effectiveness of alternative methods and materials. As part of thisresearch, a user-friendly software package named ConcreteWorks has been developed thatallows users to compare how different materials and construction techniques affect thestructure’s durability against several causes of premature deterioration.This chapter gives an overview of some of the commonly occurring causes of prematureconcrete degradation. Chapter 2 presents the heat of hydration model developed and the researchbehind it. Chapter 3 details the temperature prediction model developed for ConcreteWorks andprovides comparison with field site data. Chapter 4 explains the various early-age models thatcombine to estimate the in-place performance of a specific concrete member. Chapter 5 providesinsight into the uses of the program. Chapter 6 describes how the project outcomes should beimplemented, including proposed specification changes. Chapter 7 provides a summary, anexplanation of economic benefits, and recommended further research.Much more detail on the laboratory evaluations, field studies, and modeling efforts canbe found in Ph.D. dissertations by Poole (2007) and Riding (2007), as well as MS theses byWhigham (2005) and Meadows (2007).1.1 Thermal Cracking1.1.1ProblemA large amount of heat is released during the chemical reaction between cementitiousmaterials and water. The heat released during this chemical reaction known as hydration will noteasily dissipate in large concrete members, thus raising the concrete temperature significantly.Large internal stresses can be generated in the concrete because of the non-uniform temperatureand stiffness development in the concrete members. Cracking can occur when the concreteresidual stress exceeds the concrete tensile strength. A recent example of thermal cracking in ahighway structure in Houston highlights the risk posed by thermal cracking. Figure 1 shows thevertical thermal cracks that were found in a column in this structure. By engineering andoptimizing the construction methods and concrete materials used to control the concretetemperature and internal stress development, the risk of cracking can be substantially reduced.1
Figure 1.1Thermal Cracking in a column in the IH-10 in Houston, TX (photo courtesy of J.C.Liu)Thermal cracking in mass concrete elements has been recognized since the beginning ofthe twentieth century, when it was first discovered in dams (ACI 207 2005). Thermal gradientsin bridge elements were generally not considered in the United States. Recently, however, moreattention has been given to concrete bridge members as their size has grown in recent yearsbecause of structural and aesthetic reasons. The departments of transportation in the UnitedStates that have a mass concrete specification try to reduce the risk of concrete crackingindirectly by limiting the maximum temperature reached and maximum temperature differencein the concrete member (Chini et al. 2003). Owners and engineers in Europe, however, havechosen a more scientific approach for reducing the risk of thermal cracking in mass concrete.Large jobs in Europe (such as the Chunnel from England to France) conduct laboratory testingsuch as adiabiatic calorimetry and advanced cracking frame testing as well as perform a finiteelement thermal stress analysis prior to construction of a project (Poole 2007). It is not, however,cost-effective to perform a comprehensive laboratory analysis for every mass concrete memberbuilt by TxDOT. A model that can predict the heat of hydration and early-age mechanicalproperty development of concrete based on the mat
4563, Prediction Model for Concrete Behavior. The main product developed under this project is a software program, named Concrete Works, which gives laboratory technicians, engineers, and contractors a tool that combines concrete design, analysis, and performance prediction to improve and optimize the performance of concrete structures.
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