Experimental Study On Chloride Ion Erosion Of RC Members Strengthened With CFRP In Salt Spray Environment

As the outstanding characteristics such as light weight, high strength, good fatigue resistance and corrosion resistance, carbon fiber reinforced plastic(CFRP) was widely applied to strengthen reinforced concrete structures in civil engineering. However, in coastal areas, due to erosion caused by environmental chloride, concrete structure bridge often corroded, resulting in reduced structural bearing capacity and durability, structural failure in advance and other serious consequences. According to the environmental characteristics of China’s coastal areas in which large numbers of existing bridges serve, the paper took the RC members strengthened with CFL(a new type of CFRP) for study, explored the law of chloride ions corrosion through neutral salt spray test. And then through bending test, the author studied the carrying capacity of RC members strengthened with CFL which were pretreated by neutral salt spray environment. Based on these studies the author hoped to provide theory basis and experimental data for design or assessment of the RC members strengthened with CFRP used in bridge engineering. The main contents and conclusions of the paper are as follows.(1) The author designed a kind of RC members strengthened with CFL with preseted crack, and studied the effect of preseted crack to chloride ion erosion by neutral salt spray test. The test results showed, as to the RC members without strengthened with CFL, among three different widths of cracks, the crack of 1.2mm width had done the most for the acceleration of chloride ion erosion in RC members. After strengthened with CFL, when the crack width is approximately in the range of 0 mm to 0.6 mm, the CFL layer could resist chloride ion erosion the best. When the crack width reached 3 mm, the protective effect of CFL layer is not obvious.(2) Chloride ion erosion rules along the depth direction. Under the condition of without strengthened by CFL, after 30 days neutral salt spray accelerated test, the chloride ion on the surface of steel bar reached critical corroded concentration and started to corrode; while strengthened with CFL, after 50 days of salt spray accelerated test, the chloride ion erosion depth reached near the surface of steel bar. The effect of CFL on resisting chloride ion erosion is obvious.(3) Based on the diffusion model of chloride ion in RC members, the author introduced the concept of “equivalent thickness of concreteeqx ” and established the diffusion model of RC members strengthened with CFL. Through fitting the experimental data, the concentration expression of chloride ion diffusion in RC members before and after strengthened with CFL was obtained. Then the author used ABAQUS to simulate the chloride ion diffusion in RC members.(4) The author took the RC members strengthened with CFL to do bending experiment after the neutral salt spray environment pretreatment. The experiment result showed that after the environmental pretreatment, the strengthened members would destroy with three different failure modes, and the bearing capacity and stiffness will decreased continuously along with the increasing pretreatment time.