Monitoring setting and hardening process of mortar and concrete using ultrasonic shear waves

Ultrasonic wave methods have been extensively investigated for monitoring the setting and hardening process of cementitious materials. However, the commonly used P wave velocity parameter is affected by air voids in the material in the fresh state. In addition, the conventional ultrasonic wave velocity test setup typically needs access to both sides of a structural member, which is not always possible for in-situ field testing. The ultrasonic shear wave reflection method measures the acoustic property of the near surface material only. In this paper, ultrasonic shear waves, measured by embedded piezoceramic bender elements, are used to monitor the setting and hardening process of mortar and concrete. Experimental results from mortar and concrete mixtures with different water to cement ratios show a clear relationship between the shear wave velocity and the penetration resistance (ASTM C403), which indicates that the shear wave velocity is a more reliable indicator than the P wave velocity for in-situ monitoring of the setting and hardening process of cementitious materials.