Research of Corrosion Monitoring of Rebar in Concrete with Electrochemical Impedance Spectroscopy

Abstract

We developed a probe electrode for impedance measurement to investigate of rebar corrosion in concrete. Impedance measurements of the electrode in an aqueous solution simulating the transition zone of concrete and rebar interface were carried out. The charge transfer resistance R ct obtained from the two point frequency measurement results by the method developed by Haruyama and Tsuru almost agreed with R ct estimated by spectral measurement. It was also confirmed that R ct was drastically decreased by de-passivation following the decrease in pH. Furthermore, impedance measurement of the probe electrode in concrete specimen was carried out.It was confirmed that R ct was small when the depth of setting the probe electrode was shallow. It was concluded that the state of the rebar/concrete interface can be evaluated by R ct of the probe electrode installed in the concrete.

Evaluation of Chloride Ion Concentration and pH on Depassivation of Steel Rebar in Concrete Investigated by Electrochemical Impedance Measurement of Probe Electrodes

“…Details of the development of probe electrodes were previously described. 4,5) A deformed reinforcing bar (JIS standard: SD345, C: lower than 0.27%, S: lower than 0.040%, C + Mn: lower than 0.50%) was used as the electrode with a diameter and thickness of 1.0 cm and 0.8 cm, respectively. The top and bottom surface of the electrode were insulated by epoxy resin.…”

“…2, the R ct is the charge transfer resistance at the electrode/solution interface, the R sol is the solution resistance, and the C dl is electric double-layer capacitance at the electrode/solution interface. As previously reported, 4,5) the two frequencies impedance measurement was performed using the same equipment (CEM-100A). The impedance at 10 kHz and 10 mHz was automatically measured every 10 min.…”

“…( 1) by measuring the impedance of probe electrodes as previously reported. 4,5) As the electrochemical reactions at the steel rebar/electrolyte solution interface include the reaction intermediate formation, film formation, and diffusion process, 810) the interfacial impedance should be expressed by Faraday impedance or polarization resistance. In this study, the interfacial impedance is expressed by R ct to simplify the analysis.…”

“…Our group 4,5) have developed a probe electrode for corrosion monitoring of steel rebar embedded in concrete. A pair of probe electrodes is embedded near steel rebar in concrete during this measurement, and a two frequencies impedance measurement performed to obtain charge transfer resistance.…”

“…A pair of probe electrodes is embedded near steel rebar in concrete during this measurement, and a two frequencies impedance measurement performed to obtain charge transfer resistance. 4,5) In this study, the two frequencies impedance measurement of a pair of probe electrodes was implemented in a saturated calcium hydroxide solution, which simulates a concrete pore environment. The air was pumped to the electrolyte solution containing an arbitrary concentration of chloride ions during measurement to simulate the neutralization and salt damage of concrete.…”