Effect of Piezoelectric Ring Sensor Size on Early-Age Property Monitoring of Self-Consolidating Concrete

The objective of this paper is to investigate the effect of the sensor size used in the piezoelectric ring actuator technique (P-RAT) on the accuracy of shear wave (S-wave) measurements that can be used to determine setting characteristics of concrete. Three different PRAT sensor dimensions operating at different central frequencies of 25, 28, and 45 kHz (big, medium, and small PRAT; respectively) were investigated. In total, 14 self-consolidating concrete (SCC) mixtures were proportioned with slump-flow values of 600 to 780 mm (23.6 to 30.7 in.). A conventional concrete was also prepared with 220 mm (8.7 in.) slump. The quality of the transmitted signal was found to be higher when using the big P-RAT sensor where less scattering and less energy loss were obtained. This can make it easier to determine the S-wave arrival time, which is needed to calculate the S-wave velocity for concrete with relatively high precision. The setting time of concrete based on the criteria of the S-wave velocity (V-s) derivative is shown to correspond well to values evaluated using the standard penetration resistance test tested on mortar sieved from concrete. The results showed that the big PRAT sensor is suitable to determine the setting time of concrete by means of the derivative S-wave velocity (in time domain). However, the average setting time of mortar sieved from concrete determined from the standard penetration resistance occurred approximately 60 minutes later compared to the setting time of concrete obtained with the P-RAT approach. This shift can be due to the presence of coarse aggregate that can affect V-s .