Dynamic dielectric analysis during early-stage hydration of ordinary Portland cement

Abstract

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.