Monitoring Setting and Early Hydration of Cement Using Dielectric Spectroscopy

Dielectric permittivity is a promising technique for making non-destructive measurements of the setting and hydration behavior of cementitious systems. In this paper, preliminary work has been done to investigate the link between the dielectric permittivity behavior of a series of mortars of varying W/C and the setting and hydration behavior in the same mortars as observed using isothermal calorimetry and penetration resistance measurements. The dielectric permittivity of these mortars measured at a frequency of 2.45 GHz appears to be sensitive to the chemical changes experienced during setting. Regions in the dielectric behavior have been tentatively linked to the dormant period of cement hydration, the initial time of set and the peaks in isothermal calorimetry associated with C3S reaction and monosulphoaluminate formation. Dielectric permittivity also shows promise in determining the moisture content of portland cement-based systems.