Estimation of elastic modulus of cementitious materials under external sulfate attack

A module-oriented numerical method, consisting of an ionic diffusion module, a chemical reaction module and a micromechanical module, is developed in this paper to evaluate the degradation of elastic modulus of a cement mortar when subjected to external sulfate attack. The recently developed Modified-Poisson-Nernst-Planck (MPNP) model is adopted to model the ionic diffusion process in the material with cracking propagations. Chemical reactions are solved using the chemical thermodynamics, and the elastic modulus is predicted by a micromechanical method, i.e. the Mori-Tanaka method. The proposed method is employed to model the degradation of elastic modulus of a cement mortar immersed in the sodium sulfate solution for 420 days. The good agreements between the computed results and the experimental measurements validate the proposed method. Moreover, the influence of the shape of the micro-crack on the overall elastic property is also discussed.