Research On Bonding Performance Of CFRP-Concrete Interface Exposed To Sulfate Solution Under Freeze And Thaw Cycles

In recent years,the carbon fiber reinforced polymer has been widely used for reinforcing concrete structures, which dues to its light weight, high strength, easy to be cut, good durability, corrosion resistance etc. In the practical engineering structure, the destruction of concrete member reinforced with CFRP is mainly caused by CFRP-concrete interface stripping damage. Therefore, it is good bonding performance of the interface of CFRP and concrete that is the key to ensure the quality of CFRP reinforced.In general, the reinforced concrete structures are often in outdoor climates, some of which are even in the severe environment, such as high temperature, intense cold, intensive ultraviolet radiation, strong acid, strong base, seawater immersion, strong corrosive ions etc. In such severe environment, the bonding performance of the interface will significantly decline. The inland saline soil and salt lake in the western area of our country contain a lot of sulfate, which can lead to serious drum-expansion failure of concrete structure. In addition, the areas are located in the inland plateau, which always suffer from drought, bitter coldness and big temperature difference between day and night. In such areas, sulfate erosion to CFRP and concrete interface becomes more serious. So far, domestic and foreign research on the durability of CFRP and concrete interface mainly involves the durability of interface in single environment such as wet-dry cycles, freeze and thaw cycles, temperature, humidity, water environment, carbonization, ultraviolet irradiation etc. These studies mainly focus on the environment in the east coast and the influence of water, but the lack of research on sulfate erosion to CFRP and concrete interface in the western of cold and drought region. Based on the background, the bonding performance of CFRP-concrete interface subjected to sulfate and freeze-thaw cycles in the laboratory is mainly studied, the main researc h content is as follows:(1) Experiment investigation is carried out on tensile performance of CFRP subjected to the test environments such as freeze-thaw cycles in water, freeze-thaw cycle in the sodium sulfate solution. Therefore, the variation law of tensile strength, elastic modulus and elongation with the freezing and thawing times are studied.(2) Normal bonding strength tests of CFRP and concrete samples are carried out to study the effects of freeze-thaw cycles in water and in the sodium sulfate so lution on normal bonding performance. The failure process and failure were described. The effects of erosion environment on positive tensile bearing capacity, normal bonding strength and mechanism of action were analyzed.(3) By double shear test of CFRP and concrete specimen, the failure process and failure characteristic of the interface between CFRP and concrete are studied after the interface is subjected to the freeze-thaw cycles in water and freeze-thaw cycles in sodium sulfate solution. Besides, the effects of erosion environment on ultimate shearing capacity, stress-strain distribution, local bond-slip relationship, bond-slip constitutive relationship and effective bonding length are analyzed.