Interpretation of the impedance spectroscopy of cement paste via computer modelling

摘要: The d.c. conductivity, σ, and low-frequency relative dielectric constant, k, of Portland cement paste were monitored, using impedance spectroscopy, during cooling from room temperature down to -50 °C. Dramatic decreases in the values σ as great two orders magnitude, occurred at initial freezing point aqueous phase macropores larger capillary pores. This result provides strong experimental support for amplification mechanism, proposed Part II this series, explain high measured constant hydrating paste. Only gradual changes electrical properties observed below sudden drop, continued decrease. k frozen paste, a -40 °C, dominated by calcium-silicate-hydrate (C-S-H) so increased with degree hydration indicating C-S-H gel percolation threshold volume fraction approximately 15%–20%, good agreement previous predictions. Good was found between results digital-image-based model computations Freeze-thaw cycling caused drop unfrozen state, that measurements could be useful monitoring microstructural freeze-thaw other processes gradually damage parts microstructure.