Effect of Alkali-silica Reaction on Delayed Ettringite Formation in Concrete

We investigated the effects of alkali-silica reaction (ASR) on delayed ettringite formation (DEF) using mortar test pieces comprising ASR reactive aggregates with added potassium sulfate under various environmental conditions. As a result, it was observed that ASR not only promotes expansion caused by DEF, it causes the expansion to occur prematurely, even under conditions where the amount of sulfate and water supply are not significantly large. The increased DEF expansion could be attributed to microcracks accompanying the progress of ASR at high temperatures, and the decrease in the cured product's pH owing to the consumption of an alkaline component during ASR. However, the final expansion caused by DEF tended to be less in mortars where ASR had occurred.