The ac impedance response of concrete during early hydration

The complex impedance response of fresh concrete was investigated over the frequency range 100 Hz-10 MHz, together with resistivity measurements on the interstitial water phase. The work corroborates and extends previous studies both in the range of concretes tested and modelling of the data. It is shown that the contained water-phase within the concrete exerts a considerable influence of the impedance response and, as such, is related to the type of cemetitious binder. When the bulk resistivity of the concrete is normalized by that of the contained water, a direct relationship exists between this value and the fractional water content of the concrete. Possibilities exist for the application of impedance spectroscopy techniques in the quality control of structural concrete.