Study On Durability Of The Bonded Interface Between CFRP And High Strength Concrete Under Freeze-thaw Cycles And Wet-thermal Environment

In recent years, high strength concrete is developed fast, widely used in high-rise and large-span structures. However, due to the vast land and frequent natural disasters in China, Structures will be consequentially destroyed to some extent, exposed to natural and man-made environment. Therefore, the reinforcement of high strength concrete structures is an urgent research topic. Based on the merits of light weight, high corrosion resistance and fine mechanical properties, carbon fiber reinforced polymer (CFRP) has been widely used. Concrete structures strengthened by CFRP were researched widely. But the research of high strength concrete structures strengthened by CFRP is relatively fewer. Meanwhile, the perfect bonded property between CFRP and high strength concrete structures is the basis for two materials to work together. The research on durability of bonded interface is meaningful. Due to the above background, with double shear method, the bonded interface properties between CFRP and high strength concrete under the freeze-thaw cycles and wet-thermal environment were researched in the paper. And the concept of minimum bond length has been proposed in the paper and researched. The main contents are as follows:1. The durability of bonded interface between CFRP and high strength concrete subjected to different freeze-thaw cycles were studied. The test results indicate that with the increase of freeze-thaw cycles, ultimate bond load, ultimate global slip response, local shear stress, ductility and effective bond length will decrease. But it has little effects on initial stripping load. The failure modes change from adhesive debonding to shear failure of concrete.2. The properties of bonded interface between CFRP and high strength concrete subjected to wet-thermal environment were studied. The test results indicate that at room temperature, with the increase of time, it has little effects on initial stripping load, but ultimate bond load will rise. Yield ratio, ductility and ultimate global slip response will decrease. At high temperature, initial stripping load, initial stripping response, ultimate bond load and yield ratio will increase with the decrease of ductility and ultimate global slip response The higher the temperature is, the smaller the effective bond length will be.3. The properties of bonded interface between CFRP and high strength concrete with different bond lengths were studied. The test results indicate that with the increase of bond length, ultimate bond load and ultimate global slip response will grow. But it has little influence on initial stripping load and initial stripping response. During the load period, the stress transfer area and its length shows a process of dynamic change. Effective bond length and minimum bond length have fixed multiple relationships.