Performance Evaluation of Novel Alkali-Silica Reaction Inhibiting Chemical Admixtures in Cementitious Systems

Abstract

Certain salts of calcium and magnesium can mitigate alkali-silica reaction (ASR) by reducing the pH of concrete pore solution. In a previous study, eight such promising salts were identified out of more than 700 possible salts using a systematic approach. This study presents the performance of these admixtures in paste, mortar, and concrete mixtures. Paste mixtures were used to evaluate the long-term pore solution pH (up to 6 months) and pore size distribution. The flow, flow retention, setting time, and drying shrinkage were evaluated using mortar mixtures. ASR mitigation potential of these admixtures was evaluated with a highly reactive aggregate using a concrete prism test. Finally, concrete mixtures were designed with specific performance targets and evaluated for slump, plastic air content, compressive strength, and bulk resistivity. It was observed that the salts maintained a reduced pore solution pH over the long term. The pore size characteristics were found to be similar to or better than the control mixture. The salts mitigated ASR successfully and had minimal impact on workability, air content, and compressive strength. Most salts behaved as set accelerators. Drying shrinkage was found to be slightly higher when compared with the control, but within the limits specified by the standards. Overall, it is concluded that these pH-reducing admixtures can be used with minimal adjustments to concrete mixture proportioning in order to reliably mitigate ASR.