Evaluation of electrode-sample contact impedance under different curing humidity conditions during measurement of AC impedance of cement-based materials

Abstract

In this study, a simple method was proposed to calculate electrode-sample contact impedance in the cases of two-point and four-point measurements. The results indicated that when using the saturated calcium hydroxide solution (SCH) as conductive medium, the contact impedance in the four-point measurement is negligible for the impedance range of cement-based materials. The SCH can be used as a reference for correction of the contact impedance. A reasonable combination of curing humidity and different conductive media is recommended for the two-point measurement, which is suitable for testing the ACIS of cement-based materials. In a case of contact impedance not being precisely known, it is highly recommended that a four-point measurement with two different ratios of the length of the sample and the center spacing of the voltage electrodes (L/a) should be conducted to evaluate the effect of the contact impedance following the procedure proposed in this study.

Modeling and Interpretation of Responses of Concretes in Four‐Probe Impedance Measurements

“…[8] Despite the great importance of concrete materials and their characterization methods, multifrequency analysis of impedances related to exclusively bulk phases is relatively rare in the literature. [9][10][11] Many examples are associated with the experiments performed using two-or three-electrode configurations, [12][13][14][15] with equivalent circuits involving the response of the faradaic reactions at the electrodes (see, e. g. [16][17][18][19][20] ), in particular, corrosion processes in concretes under different conditions. [21][22][23][24] Such measurement schemes complicate the extraction and interpretation of the impedance response related to the concrete itself.…”

“…Despite the great importance of concrete materials and their characterization methods, multifrequency analysis of impedances related to exclusively bulk phases is relatively rare in the literature [9–11] . Many examples are associated with the experiments performed using two‐ or three‐electrode configurations, [12–15] with equivalent circuits involving the response of the faradaic reactions at the electrodes (see, e. g [16–20] …”

In situ determination of cement paste porosity in parallel with corrosion study of aluminium alloy 1100 in Portland cement pastes

“…Depending on the type of medium present in between the electrode surface and the cement-based material surface, the different approaches for determining the electrical conductivity of cement-based materials can be categorised as: (i) a direct contact method without extra medium, (ii) an indirect contact method with an insulating or conductive medium and (iii) a non-contact method with a thin air layer [58]. Either the direct contact method [59,60] or the indirect contact method [35,47,60,61] is likely to provide the needed information entangled with a large contact impedance at the electrode/sample interface. Even if the non-contact method is reported to reduce the impact of the interface, some effects associated with the interface (e.g.…”