Electro-chemical investigation for the effect of rebar source and surface condition on the corrosion rate of reinforced concrete structures under varying corrosive environments

Abstract

This paper examines the effect of elemental composition and surface conditions on the corrosion rate of reinforced concrete (RC) structures under varying severe environmental stressors (chloride and temperature). The RC specimens were cast from five steel bars (A to E) with different elemental compositions and two surface conditions (polished and unpolished). Half-cell potential, corrosion current and corrosion mass loss were measured. The highest corrosion rate was obtained for steel sources ‘D’ and ‘E’, which indicates that they are the most prone to corrosion. Both steel sources ‘A’ and ‘B’ were found to have improved corrosion behavior and low corrosion rates. Steel source ‘C’ exhibited intermediate corrosion values. Additionally, a change in the rate and gradient of corrosion was observed for different steel sources with increasing temperature, which can be attributed to the distinct chemistry and microstructure of the steel sources and their reaction to varying temperature conditions. Steels with polished and unpolished surface conditions showed a consistent difference between their magnitudes of corrosion. Regardless of the chloride content and temperature, the polished surface demonstrated better corrosion resistance and a lower corrosion rate compared to the unpolished steel surface, which can be attributed to the improved passive layer that was formed on the polished steel surface and the enhanced concrete microstructure around the rebar. The relative difference in the magnitude of corrosion for varying chloride concentrations seems to decrease with an increase in temperature.