Chloride Diffusion Analysis of Concrete Members Considering Depth-Dependent Diffusion Coefficients and Effect of Reinforcement Presence

This paper presents the results of an experimental investigation on chloride diffusion in plain concretes and reinforced concretes. Concretes were exposed to chloride environment simulated by a self-designed tidal circulation device for 35, 70, and 100 days. Chloride concentrations (Cl−) in powder samples which were milled layer-by-layer from plain concretes and drilled along the direction of rebar from reinforced concretes were measured. Cl− at the apex of the rebar were compared to that at the corresponding depth in plain concretes to study the blocking effect of rebar. Meanwhile, diffusion coefficients (Dx) at different depths were determined by applying Fick’s second law to study the depth-dependent characteristic of Cl− diffusion. The results show that along the direction of penetration, Dx decreases first and then increases; rebar does change the distribution of Cl−, and the larger the diameter, the greater the effect. The effect of rebar is not only embodied in the physical obstruction but also in the variations in concrete composition. Based on the results obtained, a quantitative chloride diffusion model considering rebar presence, depth-dependent characteristics, and time is given.