A mechanistic model of the degradation of cement-based materials subjected to sulfate attack

Abstract

The durability of concrete structures is usually threatened by sulfate attack in their service progress. However, there is still no widely accepted model that can accurately predict the process of sulfate attack on concrete. Combined the diffusion-reaction process, constitutive relationship, and fracture criterion, a mechanistic model is proposed by considering the effects of pore filled by products of sulfate attack on the diffusion coefficient and total expansion strain in this study. The establishment assumptions of model can be observed from the macro- and micromorphology of cement-based materials subjected to sulfate attack. The results show that the route of decohesion goes along the interface between the compressed degraded layer and the tensed non- degraded matrix as the triggered by sulfate attack, and the thickness of decohesion is between 50 and 400 μm. The time index used to correct the diffusion coefficient is close to −0.41, while the range of pore filling degree is 3.16–6.29% based on the debonding thickness. Compared with the Atkinson model, the degradation rate calculated from the modified model is the closest to the actual test value with an error less than 10%.