THE USE OF MICROWAVES TO DETERMINE THE FREE WATER CONTENT IN A CEMENT PASTE DURING HYDRATION
The hydration of cement is a phenomenon which can be evaluated by means of hyperfrequency dielectric measurements, but the various methods which have been developed for other types of study are not well adapted to this kind of material. A new method is proposed, that uses a parallel piped resonant cavity of varying length. The samples consist of small glass or rigid plastic tubes which have been filled with fresh cement paste to be studied. Complex dielectric constant measurements were made on three types of cement paste at 3000 mhz. They show that variations in the dielectric constant as a function of the time passed since mixing accurately reflect the cement hydration rate. This method could be applied to the control of the setting of mortar and fresh concrete. /TRRL/