Repetitive water replenishment in CO2 curing: Enhancement in carbon uptake, reactivity, crystal development, and mechanical properties of low calcium binder composites

Abstract

Water plays a crucial role in the carbonation and phase evolution of low-calcium binders (LCBs) under a CO₂ curing environment. This study aimed to improve the mechanical properties of LCB composites through repetitive water replenishment during curing and investigate their impact on microstructural phase evolution and strength development. To assess the effect of the amount of water replenished, distilled water containing 5, 10, and 15 wt% of cement paste was introduced into the samples at 1, 3, 6, and 12 h during CO₂ curing. Water replenishment significantly improved the reaction degree of the LCB, resulting in a characteristic microstructure due to the distinctive CaCO₃ growth. Notably, the samples with water replenishment exhibited a substantial increase in compressive strength, up to two times higher than those without water supplementation, after 24 h of curing. Therefore, the addition of water to LCB composites during CO₂ curing enhances the chemical reactions and refines the microstructure.