Applicability of AC impedance method for measuring time-variant corrosion rate to cracked and crack-repaired reinforced concrete

Abstract

Several models of the time-variant corrosion rate (CR) have been proposed to predict the service life of reinforced concrete (RC) structures based on polarization resistance (PR) monitoring. However, few of them have verified the accuracy by comparing the estimated corrosion weight loss (CWL) obtained from the PR monitoring with the actual CWL. In addition, few studies have measured the time-variant CR on crack-repaired RC specimens, and the evaluation of repair efficacy is clearly an essential step in the maintenance of the structures. This study aims to clarify the applicability of the alternating current (AC) impedance method, one of the PR methods, to cracked and crack-repaired RC. The CRs in such RC in an accelerated corrosion environment were measured every one to three months over three years using the AC impedance method. To confirm accuracy, the corroded area and CWL of the steel bars were measured. The results clarify that the measurement area of the AC impedance method was almost equal to the corroded area, which indicates that the corrosion area should be calculated in addition to the CWL for accuracy verification. The results also show that the AC impedance method can be applied to cracked and crack-repaired RC for measuring time-variant CR. The CR increases rapidly after crack initiation but becomes constant with time, and early crack repair can delay corrosion progress in cracked RC to the same extent as in uncracked concrete.