A poroplastic model for hygro.chemo-mechanical damage of concrete

The paper proposes an analytical model for calcium leaching of concrete due to water. The model is set in the framework of chemically active saturated porous media. Continuum damage mechanics is used in order to develop a phenomenological poroplastic model of concrete. Two forms of damaging processes are included: mechanical, modelled with two scalar damage internal variables; chemical, related to the decreasing calcium concentration in the matrix. Main ingredients of the model are: a damage-poroplastic mechanical model for concrete; a fluid motion mechanism with an explicit dependence of the permeability on the porosity and the damage variables; a diffusive-convective mechanism for ion transportation, governed by a diffusion coefficient function of porosity and of calcium concentration. The evolution of the state of the material is given by a set of internal variables including, in addition to mechanical and damage variables, porosity and calcium concentration in the solid skeleton. For them, evolution laws are provided by the relevant "elastic" mechanisms, governed by the internal energy, and dissipation mechanisms.