Prediction of early-age temperatures of blended-cement concrete

The advisability of controlling the temperature rise and fall in concrete at early age is well recognised, and the choice of an appropriate low-heat cement with suitable heat of hydration characteristics can assist in this control. This is particularly pertinent with respect to water-retaining and massive concrete structures, where the need to prevent early-age thermal cracking is paramount. Portland cement/ground granulated blast-furnace slag (PC/ggbs) or PC/fly ash cements are often used in these structures because of their low heat of hydration properties. This paper describes a study carried out to predict the early temperature rises for concrete containing different PC/ggbs and PC/fly ash cements. Current UK guidance normally requires knowledge of the proportion of ggbs or fly ash. Such information may not be available when using the recently published European standards for low-heat cements. To provide design data for these materials, cements just meeting the limiting heats of hydration for the low-heat and very low-heat classes were simulated. Temperature rises were predicted by a computer program that applied heat of hydration models to general heat flow theory with parameters to account for cement content, formwork type and section thickness.