Superior ASR mitigation by combined carbonation and prewetting curing with optimized sequence and time allocation

Abstract Alkali-silica reaction (ASR) is a major threat to concrete durability, causing internal expansion and cracking. Carbonation and pre-wetting curing show synergistic potential for ASR inhibition, but their combined mechanism and process optimization remain insufficiently explored. This study proposes a short-term combined curing strategy with a fixed 6-hour duration to suppress mortar ASR expansion. Results show that the carbonation-first, pre-wetting-second sequence effectively reduces ASR expansion, with the optimal regime (4 h carbonation + 2 h pre-wetting) achieving a 28-day expansion of just 0.001%, while single curing methods failed to meet the 0.1% limit. Microstructural characterizations suggest that the carbonation-first sequence forms a dense CaCO 3 protective layer, significantly reducing porosity and lowering the availability of calcium hydroxide. The inhibition is primarily attributed to a dual effect involving chemical consumption of calcium hydroxide and physical densification of the matrix. This study provides a basis for efficient, short-term ASR mitigation.