Sensitivity Analysis of Damage in Cement Materials under Sulfate Attack and Calcium Leaching

A numerical model developed in previous work by the authors is extended in this paper and used to evaluate the influence of several factors on the degradation of cementitious materials under the combined effects of external sulfate attack and calcium leaching. The previous model included (1) diffusion of ions in and out of the structure under concentration gradients and chemical activity gradients, (2) chemical reactions under local equilibrium condition assumption, and (3) damage accumulation using continuum damage mechanics. This paper extends the model by incorporating a continuum micromechanics based approach for assessing changes in elastic properties and strength of the structure attributed to chemical reactions. Two homogenization schemes combined with Eshelby's equivalent inclusion method are used to estimate the mechanical properties of the structure that change with time because of dissolution and precipitation of solids. Sensitivity analysis is performed by using the improved numerical model to evaluate the effects of several external and internal factors (e.g., pH and composition of the external solution, and porosity and tortuosity of the material) on the degradation of the structure. It is found that the damage progression rate is mostly dependent on relative rates of sulfate ingress and calcium leaching. The relations between the factors and the damage progression rate are observed to be significantly nonlinear. DOI: 10.1061/(ASCE)MT.1943-5533.0000407. (C) 2012 American Society of Civil Engineers.