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Electrode Configurations and Impedance Spectra of Cement Pastes.


pdf icon Electrode Configurations and Impedance Spectra of Cement Pastes. (662 K)
Ford, S. J.; Mason, T. O.; Christensen, B. J.; Coverdale, R. T.; Jennings, H. M.; Garboczi, E. J.

Journal of Materials Science, Vol. 30, 1217-1224, 1995.

Keywords:

building technology; electrode configurations; capacitance

Abstract:

Electrode effects on impedance spectra of cement pastes were investigated by two-, three-, and four point measurements without a potentiostat over the frequency range 0.01 Hz-10 MHz. Electrode immittance effects arising from highly resistive/capacitive contracts cannot be fully corrected by nulling procedures. Two-point measurements are much more susceptible to such effects than three- or four-point measurements. The three- and four-point results on pastes suggest that there is negligible high-frequency "offset" resistance, and that bulk paste arcs are not significantly depressed below the real axis in Nyquist plots. The important impedance-derived equivalent circuit parameters are bulk resistance and capacitance; offset resistance and arc depression angle may not be physically meaningful parameters. Whereas all electrode configurations give reliable values of bulk paste resistance, only the three-point configuration provides the total paste/electrode dual arc spectrum involving a single electrode. Multielectrode (three- or four-point) measurements may be necessary to establish the true bulk paste dielectric constant.