Non-Contact Measurement to Detect Steel Rebar Corrosion in Reinforced Concrete by Electrochemical Impedance Spectroscopy

Abstract

Non-contact wide-frequency-range electrochemical impedance measurements were employed to detect the corrosion of a steel rebar embedded into concrete. The measurements were performed by placing two Cu sensing electrodes at a distance of 50 mm from each other on the concrete surface immediately above corroded and non-corroded rebar portions. The low-frequency impedance related to the steel rebar/concrete interface was found to be lower in the former case, leading to the detection of corroded portions of steel rebar embedded in concrete. Such discrimination was only possible at cover thicknesses of up to 50 mm (cf. inter-electrode distance), as at higher thicknesses, a large fraction of current flowed directly from one electrode to the other one. This demonstrates the importance of selecting the proper distance between the sensing electrodes for optimal detection of corrosion portions when the cover thickness of reinforced concrete is known.

SiWa: See into Walls via Deep UWB Radar

“…For large building structures still in use, inspection by destruction is clearly not a sensible approach. As a more reasonable method, intrusive testing encompasses embedding sensors in a wall [17,19] and sticking electrodes on a wall [34,76]. However, embedding sensors into the wall and applying electrodes with conductive fluids can be costly and also degrade the structural integrity of the wall [12].…”

Evaluation of Corrosion Progress Using Multichannel Iron Wire Electrodes Embedded in a Cement Test Block

“…The corrosion condition or passive/depassivation state of the reinforcing bars has been diagnosed from their natural potential measurements using an external reference electrode [15][16][17] and a large Kelvin probe. 18) A non-contact impedance probe, 19) acoustic diagnosis, and non-destructive X-ray diagnosis 20) have also been used to assess the corrosion status. The impedance measurement is also useful because it provides considerable information on the passive/corroding states and corrosion rate of reinforcing bars.…”

Method for obtaining Nyquist plots identical to those of the three-electrode AC impedance method in concrete- embedded rebar without requiring electrical continuity

“…Since it becomes increasingly difficult to repair or reinforce the rebar as the corrosion progresses, it is important to ascertain corrosion of the rebar before corrosion cracks occur. The state of corrosion of rebar in concrete structures can be measured using the AC impedance method [1][2][3][4][5][6][7][8][9][10]. The typical three-electrode AC impedance method requires electrical continuity between the rebar and the measurement device, which may be inconvenient because the structure requires to be partly damaged by processes such as drilling.…”