Detection Method of Corrosion Site of Reinforcing Steel in Concrete By Two Electrode System

Abstract

A reinforced concrete has been used for the building structures and bridge in the world. However, the degradation of reinforced concrete related to the corrosion of the reinforcing steel in concrete is now serious problem. It is important to establish the method to evaluate the durability of reinforced steel in concrete. Dawson et al. [1] applied the electrochemical impedance spectroscopy to investigation of the corrosion resistance of reinforced steel in concrete. Koleva et al. [2] investigated the durability of the steel rebar casted mortal cylinder by the rest potential, polarization curve and electrochemical impedance measurements. The present study developed the method to determine the corroded reinforcing steel in concreate by two electrode system. Figure 1 shows the schematic of developed system in the present study. Two copper electrodes are placed on the surface of the concrete in which the steel bar was embedded. The cover thickness of concrete was 10 mm. The half side of the steel bar corroded to simulate the degradation of the steel bar. Schematic of the impedance spectrum of reinforcing steel in concrete measured by two electrode system is shown in Fig. 2. Two loops were observed in the impedance spectrum when the copper electrodes are placed on the concrete in which corroded steel was embedded. It indicated that the current flowing though the copper electrodes was flowed into the corroded region of the steel bar. The loop in the high frequency range was related to concrete and the loop in the low frequency range was related to interface of concrete between steel rebar. Reference:[1] J. L. Dawson, L. M. Callow, K. Hladky and J. A. Richardson, Corrossion/78, 125 (1978).[2] D. A. Koleva, K. van Breugel, J. H. W. de Wit, E. van Westing, N. Boshkov and A. L. A. Fraaij, J. Electrochem. Soc., 154, E45 (2007). Figure 1