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

Abstract

The main features of a numerical model that predicts the mechanisms of ionic transport in unsaturated cement systems are described. The model, called STADIUM, is divided into four parts: ionic diffusion, moisture transport, chemical reactions, and chemical damage. The diffusion of all ions present in the system is modeled by solving the extended Nernst-Planck/Poisson set of equations. The model takes into account the electrical coupling between the various ionic species in solution and chemical activity effects. The transport of water by capillary suction is described by a diffusion equation. In the model, the transport phenomena and the chemical reactions are uncoupled. Phase dissolution and precipitation phenomena are modeled through a separate chemical equilibrium code. The model considers the influence of chemically induced microstructural alterations on the transport properties of the material. A brief description of the model is presented in the first sections of this paper. Typical applications of the model are given in the last section.