Mitigating alkali-silica reaction through metakaolin-based internal conditioning: New insights into property evolution and mitigation mechanism

Abstract

This study investigates the role of metakaolin-based internal conditioning (MIC) in mitigating alkali-silica reaction (ASR) by monitoring volume expansion, cracking, permeability, strength, and microstructure of mortar containing reactive aggregates. Comprehensive insights into the mitigation mechanisms were obtained by elucidating the silica dissolution of aggregate and property evaluations of ASR gels with varying compositions. Substantial decreases in ASR expansion and cracking density up to 80.2 % and 73.5 %, respectively, revealed the robust role of MIC in ASR suppression outperforming single uses of metakaolin or lithium. A synergistic effect in suppressing multiple prerequisites of ASR was observed from the co-existing MIC and lithium, which was explained by the complementary efficiency between lithium and aluminum in suppressing silica dissolution, 55.7 % lower water uptake and 87.3 % less swelling potential of ASR gel, as well as the conversion of expansive ASR (Q3) gel into non-expansive C-S-H (Q2) phase making it a promising approach in designing durable concrete.