Identification of damage mechanisms of polymer-concrete in direct shearing tests by acoustic emission

• The damage characteristics of the polymer-concrete interface were recorded by the AE technique. • AE ringing counts and amplitude can effectively detect the first occurrence of cracks. • Generation of new cracks in the interface of polymer and concrete causes high AE activity. • The statistical damage constitutive models using AE parameters were established. As a new type of trenchless material, non-water reacting grouting polymer has been widely used in the reinforcement and trenchless rehabilitation of concrete infrastructure construction. Understanding the interfacial properties of the polymer-concrete composite structure is of great significance for assessing the serviceability and stability of concrete structures. In this paper, the acoustic emission (AE) technique was applied to monitor the interface damage and reveal the interface failure mechanism of polymer-concrete composite specimens. Direct shear tests were performed on polymer-concrete specimens with different polymer densities, and the AE technique was used to monitor the damage process. Various AE statistical parameters, such as AE ringing counts, energy, amplitude distribution, frequency and b-value, were analyzed. With the Weibull random distribution assumption, statistical damage constitutive models using AE parameters were established. The results reveal that AE events existed throughout the whole failure testing process and were the most significant in the yield stage. The interfacial damage of polymer-concrete specimens could be qualitatively predicted by the sharp increase in the accumulated AE ringing count and energy; the overall b-value of the polymer-concrete specimens with different polymer densities was the same and had a similar trend of a rapid decrease in the yield stage. In addition, the damage variable based on AE parameters can be used to better characterize the interfacial cracking process. The present study indicates that the AE technique is an effective technique in capturing crack development characteristics of polymer-concrete composite structures.