To prevent early-age thermal cracking in massive and water-retaining concrete structures, crack control reinforcement is required. The amount of crack control reinforcement needed is proportional to the temperature fall from peak temperature to mean ambient temperature (T_1). Several technical documents are available that assist in this, including CIRIA Report 91 and BD 28. However, these documents give rather scarce information with regard to blended cements. This paper describes the development of T_1 values, based on a series of heat evolution tests and established hydration models, to generate data for 'low heat' ggbs cements. The data were generated by computer programs developed and covered a range of cement combinations from 0% to 90% ggbs content by mass. Data for two formwork types, four section thicknesses and four cement contents were calculated using two methods, and the results compared with those in CIRIA Report 91. Similar results were obtained. The comparison showed that in the CIRIA Report data range, the calculation results were generally similar or slightly higher for steel formwork; whereas for other ggbs content, the estimates were compatible with the recommendations given in CIRIA Report 91. Based on the findings, the data provided in this paper may be used as supplementary design data alongside CIRIA Report 91 to enable calculations of T_1 to be made for ggbs cements meeting the 'low heat' cement class.
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