Combined impact of carbonation and crack width on the Chloride Penetration and Corrosion Resistance of Concrete Structures

Chloride-induced corrosion of steel rebar embedded in concrete is one of the major concerns influencing the durability of reinforced concrete structures. It is widely recognized that the carbonation in concrete affects the chloride diffusivity and accelerates chloride-induced reinforcement corrosion. The service load-related cracks also have a dominant influence on reinforcement corrosion. This study aims to investigate the potential impact of concrete carbonation on the chloride penetration resistance, and the rate of corrosion, in RC structures subjected to service-related cracks, which is not yet fully understood within the literature. The experimental programme involves casting concrete prisms (100 × 100 × 500 mm) with different water-cement ratios of 0.4, 0.5 and 0.6 and with four different crack width ranges (0, 0.05–0.15 mm, 0.15–0.25 mm and 0.25–0.35 mm), developed through flexural loading of prisms. These samples were exposed initially to accelerated carbon dioxide (CO ₂) environment and then exposed to the accelerated chloride environment. Carbonation depth, chloride penetration, and the degree of corrosion (using half-cell potential and linear polarization resistance) were experimentally measured. The results indicated that (i): The depth of carbonation increases with the increase in crack width and w/c ratio, (ii) chloride penetration depth and chloride concentration profile in concrete structures increases significantly due to the influence of carbonation and (iii) half-cell corrosion potential and linear polarization resistance increases significantly when carbonated concrete samples are exposed to the chloride environment relative to the uncarbonated concrete samples.