Effects of w/b ratio, fly ash, and chloride content on corrosion of reinforcing steel

Abstract

To predict the corrosion of reinforcing steel, the electrochemical properties of reinforcing steel with different concrete mix proportions and chloride content were studied. The water to binder ratio of concrete was varied (0.45 and 0.60). Coal fly ash was used to replace OPC (0 and 30% by weight of the total binder). The initial chloride was 0, 2, and 4% by weight of concrete. Potentiodynamic polarization testing was conducted by controlling the moisture of specimens. The Tafel slope, corrosion potential, and corrosion rate were analyzed from the testing results. Results show that chloride content significantly affects the electrochemical properties of reinforcing steel. The anodic Tafel slope decreased as chloride content increased. The cathodic Tafel slope increased when the water to binder ratio decreased, or when the fly ash content increased due to a denser concrete pore structure, limiting oxygen diffusion. Results from this study can be used to simulate the corrosion of reinforcing steel and predict the service life of reinforced concrete structures. Also, the electrochemical compatibility between existing and repaired sections can be evaluated to ensure the durability of repaired RC structures.