Investigation of the CFRP-concrete interfacial performance under adhesive curing using the PZT-based wave propagation technique

Structural adhesives were widely employed to apply fiber reinforce polymer (FRP) to concrete for structural strengthening purposes. However, the influences of adhesive curing duration on the development of CFRPconcrete interfacial performance remained unknown. This study aims to investigate the bond behavior of CFRP-concrete interfaces with various adhesive curing periods using a piezoelectric (PZT)-based wave propagation (WP) technique. The CFRP-concrete composite specimens were cured for up to 10 days and then subjected to single shear tests. The results demonstrates that the interfacial mechanical properties developed quickly in the initial three days of curing and subsequently stabilized. The failure mode shifted from adhesive failure to cohesive failure following appropriate curing for 3 days. A generalized method provided in the existing literature was employed to obtain the bond-slip relationship with different curing periods. Furthermore, the PZT-based WP technique was utilized to monitor the interfacial bond development during adhesive curing and interfacial mechanical performance under single shear tests. It can be observed that the WP technique effectively tracked the interfacial performance during adhesive curing and single shear tests. Additionally, semi-analytical relationships were established between the WP monitoring results and the interfacial performance. These findings highlight the potential of the WP technique in predicting the interfacial performance of CFRP strengthened concrete structures.