Developing a novel expression for chloride ion concentration threshold in reinforced concrete: Integration of electrochemical analysis and time-dependent modeling

Abstract

Chloride ion concentration threshold is a crucial parameter for evaluating the durability of reinforced concrete. This study aimed to develop a novel expression method for this threshold by analyzing the open-circuit potential of steel in simulated mortar pore solution across three pH values. Concurrently, the correlation between pitting potential and chloride ion concentration was examined through potentiodynamic polarization testing. Additionally, Mott-Schottky analysis facilitated the investigation of the passivation film structure on the steel under both passivation and depassivation conditions. By integrating the analysis of the open-circuit potential and pitting potential models in the simulated solution, a time-dependent relationship curve between the chloride ion threshold and time was established. The findings reveal that the steel’s passivation film comprises a dual-layer structure, with its corrosion resistance enhancing as the pH value of the simulated mortar pore solution increases. Furthermore, within the simulated mortar pore solution, the chloride ion concentration threshold exhibited a decreasing trend over time, suggesting a minimum threshold value exists. This research provides a significant foundation for forecasting the corrosion state of steel in steel-reinforced engineering projects.