Corrosion of steel rebar in concrete induced by chloride ions under natural environments

In-lab accelerated steel rebar corrosion tests have greatly deepened the understandings in corrosion behaviors, but remain still far from being filling the gaps between the corrosion mechanisms and the performance of concrete structures under natural environments. This paper reviews and analyzes the previous research of steel corrosion in reinforced concrete under natural environments, focusing on corrosion rate, microstructure at the steel-concrete interface, rust composition and properties, accelerated techniques to reproduce natural corrosion characteristics, predictive models and corrosion repair technology. Natural corrosion data of steel rebar in concrete collected from various field exposure stations across China are compiled and analyzed. Natural corrosion rate of steel in concrete tends to decrease over time in long terms. The non-uniform distribution of multilayer corrosion products at the steel-concrete interface causes rapid development of cracks. How to obtain the corresponding relationship between laboratory acceleration techniques and steel corrosion under a specific natural environment would be the important tendency of future research. Post-repair durability behavior assessment system of existing technologies needs establishment.