Corrosion rate of ordinary and high-performance concrete subjected to chloride attack by AC impedance spectroscopy

Corrosion of reinforcing steel in concrete is studied by using AC impedance. Subjected to different conditions and chloride concentrations, a laboratory study was conducted to estimate the corrosion rate of reinforcing steel embedded in ordinary Portland concrete (OPC) and high-performance concrete (HPC). One hundred and four OPC and HPC concrete cylinders embedded with a single reinforcing steel bar were exposed to sodium chloride solution with 0%, 1%, 3% and 5% concentrations. Specimens were also subjected to pre-conditioning and drying-wetting cycles. The AC Impedance technique (IS) was used to determine the corrosion rate of the reinforced concrete cylinders. In order to interpret the AC impedance spectra, several electrical equivalent circuits were employed. This investigation aims to compare IS with commonly used corrosion assessment techniques, such as Tafel plot (TP) and linear Polarization (LP). Results confirm that data obtained from AC impedance can be used to calculate the corrosion rate of reinforcing steel. A reasonable agreement with the results of TP and LP techniques is demonstrated. It is found that the corrosion rates obtained by AC impedance technique are lower than TP by 5-20%, while results of LP are 20-30% higher than those of TP. (C) 2005 Elsevier Ltd. All rights reserved.