Monitoring of Concrete Hydration by Electrical Measurement Methods

Analysis of impedance spectra of inhomogeneous materials is a part of the impedance spectroscopy which is still waiting for its development. Materials having higher electric resistance values (over 500 kΩ) can be considered - under certain simplifying assumptions – as dielectrics. A theory of dielectric polarization was formulated by Debye for homogeneous materials. Concrete setting and hardening determine the concrete quality. The impedance spectroscopy method, as one of the non-destructive testing method group, was used to characterize concrete specimens and track the changes in the concrete spectrum during the hydration process. Variances in the loss factor versus frequency tan δ(f) and impedance imaginary component Im (Z) versus impedance real component Re (Z) of the specimens under investigation have been observed. The specimen quality has been described by means of the loss type prevailing in the material. The results of this study are expected to provide information about the correlation between the n-factor (curve parameter obtained from Cole-Cole diagram) and the concrete setting time. At present, one is not able to determine unambiguously the individual material component contributions to the total electric conductivity and polarization at various frequencies of the exciting field.