In-situ crack propagation monitoring in mortar embedded with cement-based piezoelectric ceramic sensors

This paper describes a study on using embedded cement-based piezoelectric ceramic sensors to detect crack propagation in mortar specimens under cubic-splitting load by acoustic emission (AE). The main objective is to characterize the fracture process in mortar specimen in the cubic-splitting test. AE sensors (piezoelectric composites as core elements, and a mixture of cement, epoxy resin and hardener as packaging material) can be embedded into concrete and still have broadband frequency response and good matching ability with the cement material. The three-dimensional localization of the AE sources, signal-based AE energy index and variation characteristics of the AE frequency content were used to explain and quantitatively evaluate the fracture processes of the mortar specimens. The results show that the fracture processes in the mortar under the cubic-splitting are evidently brittle fracture and the variation behaviors of the AE frequency content, which exhibited a close relationship with the applied loading processes during the tests. It was also found that the application of cement-based piezoelectric ceramic sensors by means of AE represents a good option to analyze the crack growth in the specimens under increasing load, the location of the cracks and, in addition, it offers the potential for in-situ application.