Effect of hygrothermal acid rain environment on the shear bonding performance of CFRP-concrete interface

In this study, forty-five carbon fiber-reinforced polymer (CFRP)-concrete single shear specimens were designed to investigate the effect of hygrothermal acid rain environment. At first, the hygrothermal acid rain environment was simulated through a mechanical high-temperature dry-wet cycle and by artificially preparing acid rain solution with a pH value of 1.5. Subsequently, the effects of concrete strength and corrosion times on the interface failure mode, bond shear capacity, ultimate displacement, load-displacement behavior, and strain distribution in bonding interval were studied through the single shear test of CFRP-concrete. Then, the interface constitutive relation model was built based on the influence coefficient of hygrothermal acid rain. Finally, a reference method was proposed to divide the corrosion degree in hygrothermal acid rain environment, and the interface failure mechanism was expounded using a scanning electron microscope (SEM) for detection. The results indicated that the interface bonding performance was enhanced with the increase of the concrete strength, and the interface peeling position tended to change to the adhesive layer. The interfacial bonding performance increased first and then decreased with the increase of the corrosion times. When the corrosion number reaches ten cycles, the interfacial bond performance gets the best, the interfacial peel load and ultimate displacement of the three types of strength concrete(C30\C40\C50) were examined as 3.04 %, 3.50 %, 5.78 %, and 0.50 %, 0.49 %, 0.95 % higher than those of the uncorroded specimens, respectively. The SO42- ions in the acid rain invaded the surface of the concrete to synthesize an expansive substance CaSO4 center dot 2H(2)O, thus temporarily enhancing the interfacial bonding performance at the early corrosion stage. The load-displacement curve comprised four stages, including rising, oscillating, strengthening, and falling. In this study, an interface constitutive model was proposed based on the influence coefficient of hygrothermal acid rain, which is well consistent with the existing experimental data and exhibits high accuracy and safety. The relevant research results can provide theoretical support and design guidance for CFRP reinforcement projects in high-humidity and high-heat acid rain areas.