Steel Reinforcement Corrosion in Fatigue-Damaged Concrete in a Carbonation Environment

With respect to safety-critical infrastructure such as nuclear power plants, offshore wind turbine platforms, and cross-sea bridges, the coupled effects of carbonation, corrosion, and fatigue may lead to catastrophic failures. In this study, an experiment involving 14 reinforced concrete beams was conducted to investigate the indirect coupling effect of fatigue damage and a carbonation environment. On the basis of the results of the fatigue damage tests, porosity was selected as the damage variable. Finally, based on the electrochemical principles of reinforcement corrosion and considering the impact of fatigue damage on oxygen diffusion, a corrosion-based electrochemical model for reinforced concrete under the coupled effects of fatigue damage and carbonation was established, along with a numerical simulation. The key factors influencing the reinforcement corrosion behavior were also analyzed. (1) The oxygen concentration distribution at any position on the steel reinforcement surface within the concrete increased with increasing damage, whereas the lowest oxygen concentration occurred at the interface between the anode and cathode. The corrosion current density on the steel reinforcement surface reached its maximum value at the anode–cathode interface, and the average corrosion rate increased with increasing damage. The corrosion rate of steel reinforcement in concrete with 82.5% damage was up to 18% higher than that observed in undamaged concrete. (2) When the saturation rate s < 0.7, the corrosion of the reinforcing steel in concrete was mainly controlled by its resistivity, and the corrosion current density increased with increasing saturation; when the saturation rate S > 0.7, the corrosion process was controlled by cathodic oxygen diffusion, and the corrosion current density decreased with increasing saturation. (3) Compared with the effect of temperature, the influence of fatigue damage on the corrosion potential was weaker. The average corrosion current density increased with both temperature and fatigue damage. For concrete with 82.5% damage, the average corrosion current density was 0.00265 A/m² at a certain temperature and increased to 0.00315 A/m² at a higher temperature, representing an increase of approximately 20%. (4) When the concrete was undamaged, the average corrosion current density of the reinforcing steel anode continuously decreased as the thickness of the concrete cover increased. However, after the damage level increased, the average corrosion current density of the anode initially increased but then decreased with increasing cover thickness. The results of this study provide a theoretical basis and a reference for the safe operation and maintenance of major engineering projects.