Precision of existing hydration heat models for Portland cement in capturing the effects of supplementary cementitious materials and retarders

摘要

A great deal of effort has been made in previous studies to develop numerical simulation models to predict the risk of early age thermal cracking in concrete. A major input to such models, which significantly affects the temperature rise predictions and thus, the results of the analysis, is the hydration heat estimate. The precision of hydration heat estimation models for different cement compositions has been extensively verified in previous studies. However, little has been done to investigate the accuracy of such models for concrete mixes containing supplementary cementitious materials and retarders, which are commonly used in practice to minimize the risk of thermal cracking. In this paper, the results of an experimental study conducted to evaluate the capability of existing hydration heat prediction models in capturing the effects of Supplementary Cementitious Materials (SCMs) and retarders on hydration heat of general purpose Portland cement are presented. The effects of addition of various amounts of Class F Fly ash, Ground Granulated Blast Furnace Slag (GGBFS), as well as a number of common retarders including Citrate, Retardant N (Sika) and Sucrose on the hydration heat profile of cement over a period of six days was investigated using a TAM Air isothermal calorimeter. Comparing the experimental results and predictions of existing hydration heat models reveals the possibility of considerable errors in estimating the hydration heat and, thus the risk of early age thermal cracking, for concrete mixes containing SCMs and retarders.