Time-and-Depth-Dependent Model of Chloride Diffusion Coefficient for Concrete Members Considering the Effect of Coarse Aggregate

Abstract

Chloride-induced reinforcement corrosion is one of the major causes of durability failure of concrete structures in a salty environment. Because concrete is a kind of heterogeneous material, the effect of coarse aggregate on chloride diffusion cannot be ignored. This paper presents the results of an indoor experimental investigation on chloride diffusion in concrete specimens with continuously graded coarse aggregate. Concrete specimens with different coarse aggregate volume fraction (CAVF) and various maximum sizes of aggregate (MSA) were exposed in a self-designed tidal cycle device, where the chloride environment of a tidal zone was simulated, to determine the chloride concentration profile along depth for 3, 6, 9, 13, and 17 days. A time-and-depth-dependent chloride diffusion coefficient was determined using the Boltzmann–Matano method in terms of the chloride measurements. CAVF and MSA impact factors were obtained on the basis of statistical analysis. The results show that the chloride diffusion coefficient increases initially and becomes stable afterward along the penetrating direction, but decreases as CAVF or MSA increases. Based on the aforementioned results, the authors propose a time-and-depth-dependent model of a chloride diffusion coefficient considering the effect of coarse aggregate, which is called the T-D model.