Noninvasive Surface Measurement of Corrosion Impedance of Reinforcing Bar in Concrete— Part 3: Effect of Geometry and Material Properties

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Title: Noninvasive Surface Measurement of Corrosion Impedance of Reinforcing Bar in Concrete— Part 3: Effect of Geometry and Material Properties

Author(s): Jieying Zhang, Paulo J. M. Monteiro, H. Frank Morrison, and Mauricio Mancio

Publication: Materials Journal

Volume: 101

Issue: 4

Appears on pages(s): 273-280

Keywords: bars; corrosion; nondestructive testing; reinforcement

Date: 7/1/2004

Abstract:
The authors’ laboratory experiments have shown that valuable information on the corrosion of reinforced concrete can be obtained by placing four electrodes parallel to the reinforcing bar on the concrete surface and measuring impedance. Mathematical modeling has confirmed that any change in the interfacial impedance at the reinforcing bar/concrete interface can be captured from the measured impedance on the concrete surface. For the four-electrode configuration, both the electrical capacitance and resistance of the measured impedance become geometry dependent and it depends on the interfacial impedance, the measurement geometry, and the concrete material property. To illustrate this dependence, the paper presents both experimental results and numerical simulations to show how the geometry and the concrete property affect the surface-measured impedance for a constant interfacial impedance. The considered variables include the relative direction between the electrode array and the reinforcing bar, the ratio of the electrode distance to the concrete cover, and the concrete resistivity. The model in another study by three of the authors has been used to simulate the impedance responses from the constant interfacial impedance as a function of the aforementioned variables. The study of the geometric effect can help to interpret measured data and optimize the measurement setup, and it can also derive the embedded reinforcing bar’s position and the depth of concrete cover.