An Experimental Study on the Combined Effect of Curing Duration and Cyclic Wetting-Drying Ratios on Chloride Ingress in OPC Concrete

The durability of reinforced concrete structures in chloride-rich environments remains a global challenge for sustainable infrastructure. The service life of such structures is critically reduced by chloride-induced corrosion, a process that is greatly accelerated under cyclic wetting and drying. Although the importance of proper curing is well recognized, its interaction with realistic exposure conditions in controlling chloride ingress is not yet well understood. This study examines the combined effects of curing duration and exposure cycles on chloride transport in Ordinary Portland Cement (OPC) concrete. Cylindrical specimens (w/c = 0.55) were water-cured for 30 and 90 days and then exposed to chloride environments under continuous immersion and cyclic wetting–drying. The results show that frequent wetting accelerates chloride ingress through moisture-driven suction, while extended curing refines the pore structure and limits internal transport. However, the denser microstructure also promotes higher surface chloride accumulation as ions concentrate near the outer layer. Overall, the findings indicate that curing age shapes both internal resistance and surface behavior, reflecting the time-dependent development of concrete and its role in achieving resilient and resource-efficient infrastructure.