Effect of Feldspar Dissolution on Alkali–Silica Reaction at Elevated Temperatures

Abstract

Two feldspars were used as fine aggregates and cement replacement to explore the effect of feldspar dissolution on alkali–silica reaction (ASR) expansion at elevated temperatures (38°C and 60°C). At elevated temperatures, feldspar dissolution increased alkali concentration in pore solution significantly but did not increase ASR expansion of fused silica aggregate. On the contrary, feldspar dissolution even reduced ASR expansion, and the reduction in ASR expansion is more significant at 60°C than at 38°C. The mitigating effect can be attributed to the increase of Al concentration in pore solution resulting from feldspar dissolution because aqueous Al limits the dissolution of reactive silica contained in aggregate. The impact of feldspar dissolution on pore solution may lead to incorrect identification of field-deleterious feldspar-bearing aggregates as nonreactive ones.