The combined effect of alkalis and aluminum in pore solution on alkali-silica reaction

This study aims to explore the impacts of alkali ions and aqueous Al species in pore solution on alkali-silica reaction (ASR). Wrapped accelerated mortar bar test (100% RH, 38 °C) was carried out on mortars prepared with binders containing various metakaolin (0% and 5%) and alkali content (Na2Oeq = 0.65%, 1.25%, 2.25%, and 2.75%); solid and aqueous compositions of the corresponding hydrated pastes were analyzed using XRD and ICP-OES. A combined effect of alkali ions and aqueous Al species on ASR is identified, which can be characterized by a ratio of alkali (Na + K) to aluminum concentration in pore solution, and ASR expansion increases with this ratio. This finding provides new insights in understanding the relationship between pore solution composition and ASR, and indicates alternative approaches in controlling ASR, other than limiting alkalis content.