Influence of relative humidity on compressive strength of fly ash cement paste

Abstract

This study is aimed to elucidate the influence of ambient relative humidity on the compressive strength of fly ash cement paste. The ambient relative humidity has an influence on both the internal relative humidity and the hydration reaction, and further influences the compressive strength development. The experiment results revealed that the compressive strength of paste decreases with a reduction in ambient relative humidity. The same tendency can be found on the internal relative humidity and the hydration reaction as well. The detriment of strength development at low ambient relative humidity is affected by the retardation of the hydration reaction of C2S and C4AF. Moreover, the internal relative humidity at the time of test also has an influence on the compressive strength. The compressive strength decreased with the reduction in the relative humidity below the relative humidity lower man 95%. In addition, the compressive strength can be expressed as a function of the internal relative humidity and the hydrated gel volume derived from the degree of hydration of cement and the degree of pozzolanic reaction of fly ash.