Prediction of chloride ingress into blended cement concrete: Evaluation of a combined short-term laboratory-numerical procedure

Chloride-induced corrosion is commonly recognized to be a major cause of deterioration of coastal reinforced concrete structures (CRCS). Therefore, prediction of chloride penetration into concrete is a major concern in durability based design of CRCS. In this study, moisture transfer coefficient (MTC) and chloride diffusion coefficient (CDC) of some concrete specimens were determined by short-term laboratory tests and these parameters are used to numerically predict the chloride profile of the specimens subjected to long-term field tidal exposure. Thus, two series of concrete specimens with a constant water to cementitious materials ratio (w/cm) of 0.40 and different replacement levels of silica fume (SF) and natural zeolite (NZ) were prepared. The first group of the samples was exposed to the tidal condition of natural marine environment of the Qeshm Island, located in the south of Iran, for 50 months after curing in laboratory, while the second group of the samples was prepared for short-term laboratory tests to determine the MTC and CDC. Moreover, a finite element based convection-diffusion model was developed to predict the chloride penetration in the long-term field exposed specimens using short-term laboratory-determined MTC and CDC. The long-term field test results confirmed the feasibility of the proposed combined short-term laboratory-numerical procedure. In addition, the results showed that the chloride concentration decreased in the diffusion zone and increased in the convection zone with increase of SF replacement level of up to 10%. The similar trend was also observed for NZ mixtures with replacement level of up to 20%.