Numerical Modeling of Coupled Hygromechanical Degradation of Cementitious Materials

A coupled hygromechanical model for finite-element analyses of structures made of cementitious materials such as concrete or plaster is formulated within the framework of thermomechanics of partially saturated porous media. A multisurface elastoplastic-damage model, formulated in the space of plastic effective stresses, is employed to describe the nonlinear pre- and postfailure material behavior of concrete, taking the degradation of stiffness as well as the growth of inelastic strains as a consequence of the opening of microcracks into account. From relating stress and strain quantities defined on the mesolevel to respective homogenized quantities on the macrolevel, the hygromechanical coupling coefficients are identified. The effect of cracking on the isothermal liquid permeability is also accounted for. As a representative example, a two-dimensional simulation of a base restrained concrete wall subjected to both uniform drying and to rewetting at the foundation is described in the paper.