In this contribution a possibility of using an ultrasonic wave reflection method (USWR) to evaluate microstructural changes during the early age hydration process of cement paste will be presented. The method is materialized in a specially designed instrument ‘USWR-4 Hardening meter’. With the apparatus the changes in amplitude and phase shift of ultrasonic shear waves upon reflection can be measured in real time simultaneously and continuously during hydration from the first contact of cement with water. The reflection coefficient changes with time are related to the time growth of viscoelastic shear properties of the cement pastes. The method and the apparatus are very sensitive to parameters like cement type, w/c ratio, temperature, cement fineness and amount of C3A. A possibility of using USWR method to estimate the initial and final setting time is also demonstrated.
B.03 Paper at an international scientific conference