Durability enhancement and prediction model of CFRP-masonry interface in plateau climate: Application of nano-MMT/ZnO hybrid epoxy

The durability of CFRP-strengthened masonry in high-altitude plateau climates is severely compromised by coupled intense UV radiation and hygrothermal cycles. Existing studies on FRP-masonry interfaces mostly focus on isolated environmental factors or on modifying the bonding epoxy with single-type nanofillers. Research on hybrid nanofiller systems under coupled plateau aging remains limited. To mitigate interfacial degradation, this study develops a novel epoxy adhesive modified with hybrid nano-montmorillonite (MMT) and zinc oxide (ZnO). The optimized formulation (M4-Z1-EP, containing 2 wt% nanofiller at 4:1 MMT:ZnO ratio) yielded superior mechanical performance, increasing tensile and flexural strengths by 53.57% and 40.18% over the control epoxy, while reducing UV transmittance by 40.74% via a robust shielding effect. Under simulated 12-month plateau aging, the interfacial bearing capacity exhibited a non-linear decay (max reduction of 60.73%), primarily within the first six months, accompanied by a failure mode shift from cohesive brick shearing to adhesive debonding. Finally, a dual-parameter time-dependent prediction model incorporating the mortar area ratio ( ω ) and environmental aging factor ( η ) was proposed. This model demonstrates high accuracy ( R ² = 0.993), providing a theoretical basis for durability design in plateau regions.