Corrosion of Stirrups under Different Relative Humidity Conditions in Concrete Exposed to Chloride Environment

This paper aimed to investigate the corrosion mechanisms of stirrups in concrete, considering the macrocell current between stirrup and longitudinal rebar. The impacts of relative humidity (RH) and area ratio of stirrup to longitudinal rebar were studied. To avoid mechanical damage like bending on the corrosion activity of stirrups, straight stirrups were used in concrete specimens. Corrosion experiments of concrete were carried out under a simulated marine atmospheric environment. Measurements of polarization curves and macrocell currents were performed to calculate the increase of the total anodic current of stirrups due to the macrocell current by means of curve-fitting analysis. The results showed that the microcell corrosion is the major mechanism in the corrosion of stirrups under different RH conditions. Results also indicated that as RH increased, microcell and macrocell corrosion current densities increased, whereas the galvanic coupling effect that was used to quantify the increase of the total current density of stirrups decreased.