Influence of the coupled time and concrete stress effects on instantaneous chloride diffusion coefficient

Chloride ion penetration can cause corrosion of steel embedded in concrete in chloride-laden environment. Investigating the model of chloride diffusion is of vital importance to durability assessment and residual service life prediction of concrete structures. In this paper, firstly, a calculation method of instantaneous chloride diffusion coefficient (D-ins) is established based on the apparent chloride diffusion coefficient (D-a). Then, the existing experimental data in the literature are used for studying the influence of the coupled time and concrete stress effects on D-ins, and the theoretical model of D-ins is established. Finally, based on the established model of D-ins, a prediction model of chloride concentration is proposed and the model is validated by two sets of experimental data. By comparative study with experimental data, the results show that the calculation method of D-ins is reasonable and feasible, and D-ins is smaller than D-a at the same exposure time. Generally, the relative error between D-ins and D-a increases with the exposure time under the same tensile or compressive stress level, while at the same exposure time, it first increases and then decreases with increasing concrete tensile stress level, whereas it decreases with increasing concrete compressive stress level. It is found that D-ins has strong time and stress dependence. The computed results of the proposed chloride ion concentration model agree well with the experimental data. (C) 2019 Elsevier Ltd. All rights reserved.