Effect of saturation degree on chloride transport in mortars under two conditions: diffusion and continuous immersion

In actual engineering, most concrete structures are unsaturated, and the transport of harmful media in concrete highly depends on its saturation degree. In this study, chloride transport in mortars with different saturation degrees (0, 0.2, 0.4, 0.6, 0.8, and 1.0) under two conditions was investigated. One condition was that the mortars did not exchange moisture with the outside and that the internal saturation degree was constant. The other was that the mortars were continuously immersed in 3% NaCl solution, meaning that the saturation degree increased gradually. The chloride content distribution in mortars was obtained for exposure times 6, 18, 30, and 44 weeks. From the values obtained, the relationship between the relative chloride diffusion coefficient and initial saturation degree was established. Meanwhile, based on the diffusion mechanism and the capillary effect, a convection-diffusion numerical model was proposed to simulate chloride transport in mortars. The simulation results agreed well with the experimental results, especially at depths of 0-15 mm. This work aims to make a further understanding of chloride transport in concrete, and is of great significance to assess the durability and predict the service life.

Automated summary

This study investigates the transport of chloride ions in mortars with different saturation degrees. The relationship between the relative chloride diffusion coefficient and initial saturation degree is established, and a numerical model for simulating chloride transport is proposed. The results of this research contribute to a better understanding of chloride transport in concrete and have important implications for durability assessment and service life prediction.