The variations of ultrasonic velocity and attenuation, complex dielectric constant, and heat evolution rate were measured during hydration process of ordinary portland cement (O.P.C) with ratio of water to cement (by weight) ranging from 0.4 to 0.6 in the environmental temperature ranging from 20 to 40℃.
The changes of heat evolution rate during hydration indicate the kinetics of hydration and this measurements are sensitively affected by W/C ratio and environmental temperature.
The variations of ultrasonic velocity and attenuation indicate the setting stage and hardening stage. The dependence of ultrasonic velocity on W/C ratio and environmental temperature are shown to be sensitively related to concentrations of various phases depending on the extent of hydration. The variation of complex dielectric constant during hydration for frequency ranging from 10kHz to 1MHz agrees to Debye's dipole relaxation model for the change of the relaxation time resulted from the change of the viscosity, which depends on the W/C ratio and enviromental temperature, during hydration.
