Simulation Study on Diffusion of Chlorides in Concretes with Load-Induced Heterogeneous Stress

Abstract

Ingress of chlorides (Cl−) in concretes is influenced by external applied loads, and it is difficult to conduct a quantitative conclusion via experiments due to the geometry of concrete components and their different mechanical and chemical properties. To assist in-depth understanding on Cl− ingress in loaded concretes, a numerical model considering different mechanical and transport properties of three concrete components (paste, aggregate, and interfacial transition zone), heterogeneously distributed stress generated by axial loads and the consequent change in Cl− diffusion property at micro level, is established with COMSOL. Its accuracy and functionality have been verified with lab-based results from compressed and tensile samples at a macro level. The obtained results suggested that the model can effectively reveal stress distribution, generation, and propagation of cracks and Cl− diffusion in loaded concretes. Based on this model, it can be deduced that without considering the heterogeneous mechanical and transport properties of concrete components, the extent of Cl− ingress in concretes could be quite close when the induced stress is lower than 40% of the ultimate damaging stress; in comparison, it would be underestimated once the compressive or tensile loads exceed 60% of the ultimate damaging stress. Under 60% compressive loads, the Cl− ingress depth is decreased by 66%, while that is increased by roughly 40% for a 60% tensile loads.