Transport Behavior of Sulfate Ions in Concrete Subjected to Chloride Ions: A Mesoscale and Multiphase Model

The normal service life of RC structures in marine environments is significantly influenced by chloride and sulfate corrosion. In this paper, based on a self-developed program, a multiphase aggregate model consisting of aggregates, mortar, interface transition zone, and pores is established. A finite-element model was developed, and a mesoscale numerical model based on the influence of chloride on sulfate erosion of concrete is proposed. The diffusion properties of ions inside various components and the change in the diffusion coefficient with erosion time are taken into account in the model. The model was validated against third-party experimental data. The main factors affecting the ion transport and concrete damage were examined. The results showed that the aggregate model that considers the existence of interior pores yields somewhat better computational results than the model that does not. With increasing aluminate content, the sulfate ion concentration decreased by 56.97% at 6 mm erosion depth. Increasing the temperature from 273 K to 303 K resulted in 104% increase in sulfate ion concentration and 82% increase in chloride ion concentration at 6 mm depth. In addition, the range of the area in which the strain occurs is about 7 mm with increasing the aluminate content. The study offers a valuable reference for the design of RC structures in coastal environments, providing insights into their durability performance and service life prediction.