Monitoring early age microstructure development of cement paste using bender elements

Ultrasonic waves have been used to monitor early age microstructure development in cementitious materials. The conventional ultrasonic setups typically measure longitudinal (P) waves in fresh cement pastes and need access two sides of the specimen. This type of setup is not suitable for in-situ field testing. In this study, embedded piezoelectric bender elements were used to generate and measure both P and shear (S) waves in fresh cement pastes. The shear waves were observed at very early age of the cement hydration. The velocities of P and S waves 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 of cement pastes and less affected by air contents than the P wave velocity. Shear modulus and Poisson's ratios of the cement pates are derived from the measured P and S wave velocities.