Accelerated chloride-induced corrosion of hot-dipped galvanized reinforcements and its influence on bond strength to concrete

Abstract

This work studies the behavior of hot-dipped galvanized steel against chloride corrosion and its effect on its bond strength to concrete. Chloride-induced corrosion was accelerated using an electrical field. Two steel diameters were adopted and bond strength was assessed using a standardized pull-out test, followed by measuring different degrees of reinforcement corrosion. Results show that the initial corrosion of hot-dipped galvanized steel, due to the high alkalinity of fresh concrete, does not affect the performance of reinforced concrete and that galvanized steel has superior bond strength to concrete than non-galvanized steel. The relationship between the degree of corrosion of galvanized reinforcement and its bond strength to concrete occurs according to a regular pattern, independently of the diameters of the reinforcements. The pattern shows an initial increase in bond strength, followed by a stabilization region and then a region where the bond strength decreases with the increase in degree of corrosion. Experimental results also show that the corrosion process of galvanized steel may be represented by an adaptation of Tuutti’s model that shows all the phases of the corrosion process: zinc passivation period, initiation period, depassivation of zinc layer, corrosion propagation of zinc, simultaneous depassivation of steel, and corrosion propagation of steel.