Effect of hygrothermal aging on the bonding performance of glued concrete structures: A combination of experiment and molecular simulation

The bonding performance between the epoxy adhesive and concrete interface is a critical factor. However, hygrothermal aging negatively affects the bonding performance of the epoxy joint. This paper adopts a multiscale method combining macro-scale experiments with nano-scale molecular dynamics simulations to investigate the evolution patterns of failure modes and mechanical strength in glued concrete specimens under various hygrothermal aging conditions. The interaction mechanism between epoxy molecules and the C-S-H matrix was also studied. The results show that as the aging duration, temperature, and humidity of the hygrothermal aging process increased, the splitting failure mode of the specimens gradually changed from cohesive failure of concrete to mixed failure and interfacial failure. Meanwhile, the splitting strength of the specimens also gradually decreased. Under hygrothermal aging conditions of 85 °C and 95 % RH for 7, 14, and 21 days, the splitting strengths of the specimens were 2.63 MPa, 1.52 MPa, and 1.21 MPa, respectively, corresponding to strength reduction rates of 20.30 %, 53.94 %, and 63.33 %. Furthermore, moisture significantly weakened the interfacial interaction energy. Meanwhile, elevated temperature enhanced the mobility and disorder of epoxy molecules, reduced the tightness of their molecular chains, and accelerated the migration of moisture toward the interface, further deteriorating the interfacial crosslinked structure. • Thirty glued concrete specimens were tested after accelerated hydrothermal aging to assess splitting behavior. • Effects of aging duration, temperature, and humidity on splitting performance were systematically evaluated. • A molecular dynamics model was developed to clarify the mechanisms of interfacial degradation.