A multi-phase numerical simulation method for the changing process of expansion products on concrete under sulfate attack

Abstract

Concrete constructions used in harsh marine environments are commonly destroyed by sulfate ions. In this paper, by modeling aggregates as random convex polygons, to analyze and forecast the deteriorating condition of concrete under salt attack, a finite element method is suggested. The sulfate attack on concrete is studied using the numerical analytical method to examine changes in sulfate ions and expansion products at the mesoscale. Since concrete is a heterogeneous mixture, the diffusion characteristics of phases, such as the aggregate, interfacial transition zone (ITZ), mortar and pore, were considered. The proposed mesoscale numerical analysis method is validated by experiments. It is demonstrated that: (1) the setting of ITZ thickness and pore has negligible effect on concrete damage in sulfate environment; (2) reducing the water-cement ratio can significantly enhance the erosion resistance of concrete; (3) within a certain range of depth, the surface sulfate concentration is positively correlated with the erosion degree; (4) aluminate determines the peak value of ettringite content in concrete.