Modeling the behavior of unsaturated cement systems exposed to aggressive chemical environments

The main features of a numerical model that predicts the mechanisms of ioni c transport in unsaturated cement systems are described. The model, called STADIUM, is divided into four parts: ionic diffusion, moisture transport, c hemical reactions, and chemical damage. The diffusion of all ions present i n the system is modeled by solving the extended Nernst-Planck/Poisson set o f equations. The model takes into account the electrical coupling between t he various ionic species in solution and chemical activity effects. The tra nsport of water by capillary suction is described by a diffusion equation. In the model, the transport phenomena and the chemical reactions are uncoup led. Phase dissolution and precipitation phenomena are modeled through a se parate chemical equilibrium code. The model considers the influence of chem ically induced microstructural alterations on the transport properties of t he material. A brief description of the model is presented in the first sec tions of this paper. Typical applications of the model are given in the las t section.