Accelerated Alkali-Silica Reaction After a Seven-Year Asr-Dormancy Period

Abstract

The ongoing alkali-silica reaction (ASR) in concrete can be halted by dryness, which is im- portant for repairing ASR-suffered concrete structures. Drying of the concrete establishes an ASR-dormancy period until the end of the dryness. The residual expansion of such concrete after the ingress of water—the end of the dormancy period—is a significant risk, especially for repair works. In this experimental study, the post-dormancy expansion of various mixtures prepared by eight different Portland cement and three different supplementary cementitious materials (SCM) were tested using an accelerated mortar bar test. After accelerated ASR ex- pansions, an ASR-dormancy period was established by keeping the specimens dry for seven years; the residual ASR expansions of the specimens were tested by the same accelerated meth- od. The effect of pre-dormancy reactions on the residual expansions was discussed through two perspectives. The post-dormancy expansion behavior of mixtures without or with insuffi- cient SCM indicated that expansions were primarily driven by the swelling of old gel, whereas in specimens with sufficient SCM, the dominant mechanism was new gel formation, a result of lower pre-dormancy expansions due to the ASR-mitigating effect of SCMs.