Effects of Concrete Mix Proportion and Chloride Content on Electrochemical Properties of Reinforcing Steel in Concrete

Abstract

Corrosion of steel in concrete has been considered as a major cause reducing the lifespan of reinforced concrete (RC) structures. Evaluation of corrosion rate is crucial to determine service life and maintenance plaining for RC structures. Electrochemical properties of corrosion of embedded steel in concrete, including the Tafel slope, corrosion potential and corrosion current density, are significant parameters predicting corrosion rate. The objective of this paper was to quantitatively evaluate electrochemical properties of steel in different compositions of concrete. Varied parameters include the water to binder ratio of concrete, type of binder and chloride content. The electrochemical properties were evaluated at three periods of exposure. Experimental results reveal that the electrochemical properties of reinforcing steel depend on water to binder ratio, type of binder and chloride content. An increase in chloride content significantly decreases the corrosion potential and increases the corrosion rate of steel. The anodic equilibrium potential is lower with an increase in chloride content. The varied concrete mix proportion significantly influence the cathodic polarization. This is due to the effects of concrete porosity on oxygen concentration, which is influenced by the concrete mix proportions. The results can be used to predict corrosion rate of steel in various concrete mix proportion for determining service life and repairing of RC structures.