The sulphatic service environment with repetitive wetting-drying alternations will bring about severe impact to concretes’durability,so it is of great importance to study the transport mechanism of corrosive ions in concrete subjected to that working condition. Based on the transport mechanism of sulfate ions in unsaturated concrete,a 2D transport-reaction model of sulfate in concrete prism under repetitive wetting-drying alternation was established. In the model,the ion consumption caused by chemical reactions and the influence of chemical damage on ion diffusivity were taken into account. The alternating direction implicit scheme of finite difference method was used to numerically solve the transport model. The model validation was carried out by MATLAB programming,and the calculated results coincided well with the experimental data. On this basis,a numerical simulation was performed to investigate the transport behavior of water and sulfate ions in the unsaturated concrete prism under marine tidal circumstance. The results indicated that,water does not simply evaporate into environment at the drying stage,but is simultaneously transported to the surface layer and the interior of prism. The sulfate ion concentration exhibits a decreasing trend from surface to centre,which is similar to that under continuous immersion,and there is no obvious boundary between ion convection and diffusion zones inside the prism. © 2024 Cailiao Daobaoshe/ Materials Review. All rights reserved.