Effect of curing temperature and fly ash content on the hydration and microstructure of fly ash–cement pastes

Abstract

The effect of FA and curing temperature on the hydration and microstructure of FC pastes were studied by means of XRD, 29Si NMR and SEM. The results showed that with increasing FA content, the hydration degree of FA decreases, whereas the hydration of cement was accelerated. The incorporation of FA leads to an increase in the substitution fraction of Si4+ by Al3+ in aluminosilicate chains (Al[4]/Si) and also an increase in the mean aluminosilicate chain length of C-S-H gel (MCL). In the FC pastes with 30% FA cured for 28 d, with the increase of curing temperature, there is an overall increase in the MCL , the Al[4]/Si, the hydration degree of cement and the hydration degree of FA. This validated that the higher curing temperature favor more to enhance the hydration of cement, the pozzolanic reaction of FA and the polymerization of C-S-H gel for accelerated ion diffusion rate.