Electrochemical impedance analysis of corrosion of reinforcing bars in concrete

Abstract

Owing to the presence of loops related to the time constants originating from the structure and interfacial reactions, it is difficult to select a suitable equivalent circuit for curve fitting of the impedance spectrum of reinforced concrete. To investigate the time constants observed in the impedance spectrum of reinforced concrete and propose an appropriate equivalent circuit, electrochemical impedance measurements of reinforced concrete with different cover thicknesses were performed using a two-electrode system. In this case, two parallel reinforcing bars were embedded in the concrete, and a cyclic wet–dry test was conducted to accelerate the corrosion of the reinforcing bars. It was confirmed that part of the large loop in the low-frequency range was related to the reinforcing bar/ concrete interface, a distorted loop in the middle-frequency range was associated with rust formation on the reinforcing bars, and the small loop in the high-frequency range was attributed to the water distribution and pore structure in concrete.