Computational modeling of transport mechanisms in reactive porous media – application to calcium leaching of concrete

The paper is concerned with a dissociation-diffusion model for calcium leaching of cementitious materials formulated within the framework of the theory of reactive porous media. Main attention is paid to the critical investigation of different diffusion models for electrolyte solutions. This models can take the interaction of migrating electrically charged dissolution products by the electrostatic coupling, the relaxation effect and the electrophoretic phenomenon into account. It is demonstrated, that for reliable life time prognoses of concrete structures subjected to chemically aggressive media the consideration of ion-ion interactions in concentrated electrolyte solutions, resulting in a concentration dependent diffusion coefficient, is necessary. A representative numerical analysis of calcium leaching illustrates the properties and restrictions of the investigated ion diffusion models.