Piezoelectric-based Crack Detection Techniques of Concrete Structures: Experimental study

This paper presents a feasibility study for practical applications of a wave propagation-based active crack detection technique for nondestructive evaluations (NDE) of concrete structures applying surface bonded and embedded piezoelectric-ceramic (PZT) patches. At first, the wave propagation mechanisms in concrete are analyzed. Then, an active sensing system with integrated actuators/sensors is constructed. One PZT patch is used as an actuator to generate high frequency waves, and the other PZT patches are used as sensors to detect the propagating wave. Scattered wave signals from the damage can be obtained by subtracting the baseline signal of the intact structure from the recorded signal of the damaged structure. In the experimental study, progressive cracked damage inflicted artificially on the plain concrete beam is assessed by using both lateral and thickness modes of the PZT patches. The results show that with the increasing number and severity of cracks, the magnitude of the sensor output decreases for the surface bonded PZT patches, increases for the embedded PZT patches.