COMPUTATIONAL MODELLING OF CHLORIDE ION TRANSPORT IN REINFORCED CONCRETE

Exposure to a saline environment is a major threat with respect to the durability of reinforced concrete structures. The chloride ions, which are present in seawater and de-icing salts, are able to penetrate the concrete up to the depth of the reinforcement. They can eventually trigger a pitting corrosion process. The assessment of a corrosion-free service life of concrete structures is of paramount economic interest. However, the modelling of the ingress of chloride ions is complicated due to various influencing factors and transport mechanisms. Here a computational model for chloride ion transport through a porous material is presented. Chloride ion transport in reinforced concrete is modelled by focusing on centimeter-level and setting up three coupled equations for heat, moisture and chloride ion transport respectively. Three quasi-homogeneous components are distinguished: mortar, aggregates and interfacial transition zones. The model is handled computationally by discretising in space according to the finite element method and discretising in time according to the finite difference method. Stationary and transient, linear and non-linear, homogeneous or heterogeneous calculations can be performed. By applying the model a number of examples have been elaborated; one of these is presented. This example focuses on the coupling between chloride ion and moisture flow.