Effect of reverse water pressure on chloride penetration within finite concrete during drying-wetting cycles

Chloride ions invasion in a finite RC structure is significantly controlled by the hydraulic head difference between the seawater and the soil sides. In this study, the mechanism of chloride convection-diffusion penetration within the finite RC structure under the coupled effect of drying-wetting marine environment and reverse water pressure is investigated by indoor experiments and numerical modelling. The indoor exposure experiment is designed to characterize the temporal-spatial variation of chloride convection-diffusion behaviors in concrete. A chloride invasion model by considering the coupled effect of drying-wetting cycles and reverse water pressure via the COMSOL Multiphysics software is developed. The results indicated that, by comparing the application of reverse water pressure to natural drying-wetting cycles, the concrete surface chloride ion concentration is significantly reduced, and the growth of the unsaturation zone is clearly limited. Seepage pressure gradient restrains the inward transport of chloride ion in time and space within the RC structure further.