The dielectric response of hydrating cement paste has been measured in the frequency range 5 - Hz. The spectra of complex capacitance have been characterized in terms of the dispersive bulk and barrier responses at high- and low-frequency ranges, respectively, and by a generalized Maxwell - Wagner response at intermediate frequencies. We have developed a theoretical model for the bulk response of the cement paste by considering a lattice gas model for the diffusion of ions in pores exhibiting a fractal distribution in size. Using this model we have assigned physical meanings to parameters characterizing the bulk dielectric response and have determined the variation of these parameters during hydration.

Dynamic dielectric analysis and the measurement of heat evolution rate were performed during the hydration process of ordinary Portland cement with the water/cement ratio ranging from 0.4 to 0.6 at an environmental temperature of 20 degrees C. The variations of complex dielectric permittivity and its water/cement ratio dependency were analysed in terms of the Debye model of the dipole relaxation process and the effective dipole relaxation time. The dielectric permittivity at low and high frequency, epsilon 0 and epsilon infinity respectively, was approximately 160 and 80, which is nearly invariant with the water/cement ratio between 0.4 and 0.6. The calculated effective dipole relaxation time reflected the change of physical properties during hydration.