Experiment and simulation on the coupled effects of calcium leaching and chloride transport in concrete under hydraulic pressure

Abstract

This study investigated the coupled effect of calcium leaching and chloride erosion on concrete subjected to hydraulic pressure by combining experiments and numerical simulations. Several tests including titration, pH, XRD, TG, MIP, and SEM-EDS were employed to analyze chloride concentration, pH value, solid phase compositions, and microstructure of concrete under hydraulic pressure. Concurrently, a model based on the physicochemical interactions between the pore solution and the hydration products was constructed to elucidate the process of calcium leaching and multi-ion transport. The experimental and simulation results reveal that hydraulic pressure accelerates calcium leaching in concrete, leading to a maximum porosity that reaches 1.5 times the initial porosity after a year. In addition, both the pH value and chloride binding capacity in the zone close to the exposure surface decrease. The enrichment of Ca²⁺ and OH⁻ occurs at a specific depth within concrete during the calcium leaching process, and over time, this enrichment effect grows increasingly significant. Along the depth within the concrete, a transient increase in chloride binding capacity can be observed, which can be attributed to OH⁻ and Ca²⁺ enrichment.