Microstructure-electrical property relationships in cement-based materials

A recent progress on the application of impedance spectroscopy (IS) to the study of microstructure and transport in cement-based materials has been reported. With the IS spectrum, bulk resistance could be determined. The high values of the relative dielectric constant result of the microstructure inducing dielectric amplification. The role of large capillary pores in the dielectric amplification in young pastes are confirmed by solvent exchange experiments coupled with digital-image-based computer modeling. When the conductivities (ε_r) and relative dielectric constants (ε_r) of ordinary portland cement (OPC) pastes were monitored during cooling and solvent exchange with isopropanol and methanol, dramatic decreases in and as well as a secondary dielectric amplification were observed. By comparing the dielectric behavior of methanol-exchanged OPC pastes to isopropanol-exchanged OPC pastes, additional insight into the variable nature of the C-S-H microstructure was achieved.