Monitoring and evaluation of the repair quality of concrete cracks using piezoelectric smart aggregates

Various crack repair methods have been studied, but monitoring and evaluation of crack repair quality are rarely reported. In this paper, a method was proposed to monitor and evaluate the repair quality of concrete cracks using piezoelectric smart aggregates (SAs). SA can be utilized as both the actuator and the sensor in the active sensing approach, and it can be safely embedded in concrete structures due to its encapsulation properties. Moreover, the principle of stress wave propagation in the repairing process of concrete cracks was explored. Three concrete specimens with embedded SAs were fabricated and a self-made SA-based monitoring platform was constructed. The effects of crack damage, crack repair height, and repair material on stress wave propagation in concrete specimens were studied by using the monitoring platform. An energy analysis method based on wavelet packet was developed to quantitatively characterize the signal energy. Accordingly, the crack repair index was defined innovatively. Furthermore, the axial compressive strengths of concrete specimens in different states were measured. The results show that the proposed repair index can monitor the crack repair process in real time and has the potential to evaluate the repair performance of different crack repair materials.