Numerical modeling of long-term deterioration of concrete structures accounting for hygral and chemical processes

The paper describes numerical models for finite element analyses of long-term structural degradation of concrete structures, taking environmentally induced damage processes into account. A chemo-mechanical model based on the mixture theory is concerned with coupled damage processes caused by calcium dissolution-diffusion processes and mechanical loading. Coupling between both processes is accomplished by the definition of the total porosity as the sum of the initial porosity, the porosity caused by the calcium dissolution and the apparent porosity due to mechanical loading. A hygro-thermo-mechanical model is formulated in the context of the theory of unsaturated porous media using an anisotropic plasticity-damage model. The influence of moisture on the fluid-skeleton and on the material strength as well as the influence of cracks on the permeability are accounted for. For both models, the thermodynamic basis and the evolution equations are described in the paper. A representative numerical example illustrates the structural degradation of a concrete beam subjected to combined mechanical loading and cyclic chemical attack.