J. Stepišnik, Oddelek za fiziko, FMF, Univerza v Ljubljani, Ljubljana

In this work an apparatus employing a novel nondestructive method based on the reflection of ultrasonic shear waves is described. Application possibilities for studies of the early hydration processes of pastes in selected hydraulic, mostly cementitious materials are presented. These measurements demonstrate, that the shear wave method presented is quite sensitive to different parameters (composition, water/cement ratio, fineness, grain size distribution, addition of additives, temperature and humidity) which influence the hardening process of these materials. Applications to curing process following, in time domain, of some non-cement compounds will be shown. On the basis of an evaluation of these and other ongoing experimental studies a compact 'hardness and cure meter' for research and for industrial testing can be constructed.