Durability Of Bond Performance Between CFRP And High Strength Concrete Under Loading And Environmental Conditions

Recent years have witnessed the wide application of high strength concrete due to its superiority in technology and economic performance. And the issue of reinforcement of high strength concrete is becoming more attractive. CFRP has the advantages of light weight, high strength, and corrosion resistance, which is widely used for reinforcing concrete structures. In addition to forces, reinforced structures also endure the effects of erosion environment during their service. However, the studies on long term durability of CFRP reinforced concrete structures under the combination of loads and environment are still insufficient, especially for high strength concrete.In this paper, double-shear specimens were exerted sustained loads with self-designed loading device and then exposed to freeze-thaw and wet-dry cycles. The performance of CFRP-high strength concrete bonded joints subjected to sustained loads and corrosion environment is presented as follows.The influence of loads and freeze-thaw cycles on the interface between CFRP and high strength concrete was researched. The results indicate that each factor has adverse effects on ultimate load, ultimate global slip, bond stiffness, and the peak of partial shear stress, and their combination would make the degeneration more serious. Effective bond length between CFRP and concrete rises with the increase of cycles and loads. And failure mode changes from debond between resin and concrete to the shear fracture of concrete.The influence of loads and wet-dry cycles on the interface between CFRP and high strength concrete was researched. The results indicate that with the effect of loads and cycles, ultimate load generally decreases with a rise at the early stage. Wet-dry cycles have greater impact on the bond strength, and sustained loads decrease the bong stiffness. With the increase of loads and cycles, effective bond length slightly grows, and the concrete paste on debonded CFRP sheets decreases.In conclusion, the combinations of sustained loads and freeze-thaw cycles, wet-dry cycles both induce degeneration of bond performance of CFRP-high strength concrete interface. However, the mechanisms are different. As to specimens under loads and freeze-thaw cycles, decline of concrete strength is the major reason of bond degeneration, however, aging of resin induced by wet-dry cycles primarily leads to the degradation of bond performance. Thus, improving freezing resistance of concrete is an efficient method to enhance durability of CFRP reinforced concrete structures under freeze-thaw condition, and the endurance of resin is vital for their durability under wet-dry cycles.