High-frequency ultrasonic testing of young cement-based materials using the 'prism technique'

A new technique for testing young cement paste and mortar is presented. It is based on a method, which uses unconventional prism-shaped specimens. It involves the precise measurement at fixed intervals of 24 h of the time-of-flight of both compressional and shear waves using high-frequency ultrasound. A water tank was designed that allows for easy coupling and handling of the specimens. Both waves are generated by mode conversion using the same transducer. The echoes from all the specimens were strong, and no signal processing was required. Thus, reliable and repeatable results were achieved using a very basic apparatus. Second-order elastic constants were evaluated, and correlation was made with the porosity and age of mortar. A new standard based on this method is proposed which would help in the making of prediction models for evaluating the strength of cement-based materials.