Monitoring early age property of cement and concrete using piezoceramic bender elements

Ultrasonic waves are commonly used for non-destructive evaluation of concrete structures. For fresh concrete, ultrasonic waves have also been used to monitor concrete setting and strength development at early ages. However, the conventional ultrasonic test set-up typically needs access to the two opposite sides of concrete structures, which is not always possible for in situ field testing. In this paper, embedded piezoceramic bender elements are proposed to measure ultrasonic shear (S) waves in fresh cement paste, mortar and concrete. The shear wave velocities are obtained from B-scan images of a collection of recorded signals over time. Experimental results indicate that the shear wave velocity is closely related to the setting time, and this relationship is independent of air void content and w/c of cement pastes. The low cost bender elements can also be of use to monitor the setting of fresh concrete and the long term evaluation of hardened concrete.