Impedance measurements on cement paste

The present paper is devoted to the study of the high frequency region of the impedance spectrum, and focused at determining the origin of the time constants in the impedance and their relation to the dielectric properties of cement paste. The origin of the intermediate frequency capacitive range was investigated by intercalating polyester sheets between the paste sample and the graphite electrodes. It was concluded that the dielectric constant of cement paste can be determined only when impedance measurements are performed to frequencies higher than 10 MHz. Oven dried cement paste presents a single almost perfect capacitive behaviour with a dielectric constant, epsilon, below 10. In partially moistened cement paste the higher frequency range gives a reasonable epsilon (approximate to 80) for a water containing material. It is concluded that the interpretation of the high values of epsilon in terms of the DAF effect does not seem correct. (C) 1997 Elsevier Science Ltd.