Mechanisms and kinetic model for steel corrosion in unsaturated cementitious materials

Considering the complex coupling of steel corrosion in partially saturated concrete filled with water, the quantitative description of control mechanisms is still under debate. This work provides new experimental evidence supporting that diffusion control (relative diffusion coefficient) is the dominant mechanism in controlling corrosion rate by limiting the ferrous ion migration in unsaturated concrete. Furthermore, a new mechanism-based kinetic model is developed to predict the corrosion rate in different cementitious materials and corrosion conditions. In addition, the proposed kinetic model can quantify the variation of critical [Cl−]/[OH−] with degree of saturation, classify corrosive conditions, and predict the electrical resistivity and corrosion rate relationships.