Interpretation of the Impedance Spectroscopy of Cement Paste Via Computer Modelling. Part 1. Bulk Conductivity and Offset Resistance.
Interpretation of the Impedance Spectroscopy of Cement
Paste Via Computer Modelling. Part 1. Bulk
Conductivity and Offset Resistance.
(825 K)
Coverdale, R. T.; Christensen, B. J.; Jennings, H. M.;
Mason, T. O.; Bentz, D. P.; Garboczi, E. J.
Journal of Materials Science, Vol. 30, 712-719, 1995.
Keywords:
building technology; cement paste; computer models;
conductivity; hydration; impedance; spectroscopy
Abstract:
Computer simulation of impedance spectroscopy (IS) of
hydrating cement paste, using a three-dimensional,
four-phase model, is described. Two puzzling features
of experimental IS results, the possible offset
resistance in the Nyquist plot and the shapr decrease in
normalized conductivity within the first 50 h of
reaction, have been studied using the computer
simulation model. Insight is provided into these
features using the ability of the model to compare
quantitatively microstructure and properties. It is
concluded that the offset resistance is an experimental
artefact, and does not directly relate to
microstructure. The drop in conductivity during the
first 50 h is shown to be a consequence of a gradual
shift from parallel-dominated to series-dominated
behavior of the electrical conductivity, as
microstructural modifications take place during
hydration, causing the capillary pore structure to
become more tortuous. This tortuousity can also explain
the high-frequency impedance behavior in terms of a
two-arc response.
