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

Ingress of chlorides (${\mathrm{Cl}}^{-}$) 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 ${\mathrm{Cl}}^{-}$ 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 ${\mathrm{Cl}}^{-}$ 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 ${\mathrm{Cl}}^{-}$ 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 ${\mathrm{Cl}}^{-}$ 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 ${\mathrm{Cl}}^{-}$ ingress depth is decreased by 66%, while that is increased by roughly 40% for a 60% tensile loads.