Electrode Configurations and Impedance Spectra of Cement Pastes.
Electrode Configurations and Impedance Spectra of Cement
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.
building technology; electrode configurations;
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.