Abstract
This paper discusses the suppressing mechanism of supplementary cementitious materials (SCM) for expansion by alkali-silica reaction from the viewpoint of phase composition of cement hydrates. Hydration process and phase composition of hydrated cement paste were analyzed by using combined XRD/Rietveld analysis and chemical analysis. Suppressing effect of SCM was evaluated by mortar bars with 1.2% alkali and 40°C. Additionally, hydroxide ion concentration in pore solution was estimated based on the chemical composition of C-S-H gel. As the results, incorporating SCM contributed to the reduced Ca/Si ratio of C-S-H gel. The suppressing effect of SCM was correlated with the hydroxide ion concentration. These results strongly suggest that the mechanism of SCM for suppressing ASR expansion can be attributed to the reduction in hydroxide ion concentration in pore solution.
