Influence of calcareous fly ash on the temperature of concrete in massive elements during the first 72 hours of hardening

Abstract

As a measure to avoid thermally induced cracking in massive concrete, mineral admixtures are often added as a substitute for a certain portion of cement. This paper presents the results of testing in course of which the temperature was measured during hardening of concrete mixtures produced with addition of calcareous fly ash obtained from the Power Station in Bełchatów, Poland. The investigation covered 76 concrete mixtures produced with three different aggregates and diverse binder content. In the experimental part of the research, the thermal parameters of hardening concrete were determined with a specially developed method in which the mixture was placed in a one-dimensional mould which allowed for unrestrained flow of heat in one direction. The results of testing were used to assess the influence of the respective ingredients, in particular calcareous fly ash, on the rate of rise of the fresh concrete temperature, on the time of occurrence of the maximum temperature and on the temperature gradients. Finally, a formula for calculating the specific heat of hydration depending on the mixture composition was proposed.