Experimental and statistical analysis of the alkali–silica reaction of accelerating admixtures in shotcrete

This study investigated the alkali–silica reaction of accelerating admixtures for shotcrete. Tests were performed with two types of cement (low- and high-alkali) and three types of accelerating admixture (alkali-free, cement-based mineral and aluminate). An expansion test was performed to determine the alkali–silica reactivity according to ASTM C 1260. The results showed that the expansion increased with the total equivalent alkali content of the specimens. To examine this finding statistically, analyses were conducted at the 95% confidence level. When the low-alkali cement was used, no difference appeared to exist in the expansion after a reasonable period of time regardless of the accelerating admixture. In contrast, when the high-alkali cement was applied, the expansion of the specimens varied with time, although no difference was observed between the expansions of the plain sample and the specimen using the alkali-free accelerating admixture.