The effect of using internal curing on chloride penetration of self-compacting concrete

In recent years, the use of internal curing has received attention as a solution to reduce problems caused by shrinkage in self-compacting concrete (SCC). However, the use of internal curing agents increases the internal porosity of concrete, which can lead to durability issues in some environmental conditions. This study examines the effects of internal curing on the properties and durability of SCC incorporating recycled Lightweight aggregate (RLWA) and superabsorbent polymers (SAP) as internal curing agents. Mixtures containing 15% and 30% RLWA or 0.1% SAP were evaluated under both saturated and 50% relative humidity conditions. The tests included compressive strength and rapid chloride migration. The results indicated that under 50% relative humidity, internal curing agents enhanced compressive strength by up to 6.8% at 28 days and reduced the chloride ion diffusion coefficient by up to 18.4% at 360 days. Using the chloride diffusion coefficients obtained, along with the Crank-Nielsen method, the phenomenon of chloride ion penetration in concrete was modeled, and the initiation time for reinforcement corrosion was estimated. SAP extended the corrosion initiation time by 25.8% compared to Ref.-DW and demonstrated 17.2% superior durability performance compared to 15RLWA-DW. The findings show that SAP is a more effective internal curing agent for improving the durability and corrosion resistance of SCC in unsaturated environments, offering a valuable approach to enhancing concrete durability.