Experimental and simulation study on chloride diffusion in unsaturated concrete under the coupled effect of carbonation and loading

In this paper, the transport of chloride ions in marine concrete was investigated under coupled environment of carbonization and various static sustained loads. Firstly, the influences of concrete strength, exposed ages of concrete, flexural and compressive loads on chloride ion diffusion in concrete were studied by the salt spray erosion and carbonation erosion alternate test. The result showed that the content of chloride ions decreased with the increasing concrete strength, and increased with age. And the chloride ion content increased with the increase of the flexural stress and they first decreased then increased with the increase of the compressive stress level. Carbonization accelerates the chloride ion transmission and increases the chloride ion content to a certain extent under the experimental conditions. Then, the chloride ion transport equation in partially saturated concrete was formulated considering such multiple factors as carbonization, load, saturation, relative humidity and temperature. On the basis of the established chloride transport equation, the chloride diffusion process of the samples was simulated by using COMSOL software at the macro level, and the calculated results display fine consistency with experimental data. Finally, the multi-phase mesoscopic numerical models were proposed by two-dimensional meso-structure of samples with randomly distributed convex polygon aggregates. It is found that aggregate has a significant impact on the transport path and distribution uniformity of chloride ions.