Study On Bond Behavior Between Rebar And Concrete Modified With Nano-clay Under Chloride Enviroment

Large amounts of existing concrete structures are being deteriorated due to environmental exposure. The chloride ions diffuse from environment into the concrete structures, which induce corrosion of steel and degradation of bond properties between reinforcing rebar and concrete. This process leads to the deterioration of concrete structures and makes serious damage to durability of reinforcement concrete structures. It has become an engineering challenges to impede the chloride penetration into concrete and to protect the embedded reinforcement from corrosion, which has attracted extensive attention worldwide. Consequently, addition of nano-clay in concrete provides an excellent way to counteract the chloride diffusion in the concrete, which is beneficial for the durability of concrete structures. A kind of kaolinite nano-clay was applied to modify the chloride resistance of concrete in this paper. The bond property of RC structures was studied, which based on the systematic investigation of the literatures. This paper supported by the National Natural Science Foundation of China (Grant No. 51178069) and the program for New Century Excellent Talents in University (Grant No. NCET-11-0860). The main contents are as follows:1、The effects of nano-clay on the chloride diffusion depth and chloride ion content in concrete. An electrical corrosion method was used to corrode the concrete specimens with different nano-clay addition. Chloride diffusion and chloride content test were carried to evaluate the effects of nano-clay on the chloride diffusion depth and chloride ion content in concrete.2、The studies on long time monitoring of corrosion in reinforcement concrete under different additions of nano-clay. Natural soaking method was used to corrode concrete samples for a long time under different content of nano-clay in the laboratory, then the change of corrosion state of reinforcement in concrete samples was obtained.3、The effects of nano-clay on steel corrosion and the bond property between concrete and reinforcing steel were investigated. An electrochemical test including 96 cylinder specimens was designed to induce the corrosion of reinforcing bars embedded in concrete in the laboratory. Pullout tests were performed to assess the bond properties including bond-slip curve, ultimate bond strength between concrete and rebar before and after corrosion. The results showed that the use of nano-clay leads to a remarkable improvement for the bond behavior between the reinforcement and concrete. An effective delay for corrosion of reinforcement embedded in the concrete was observed. In summary, the application of nano-clay exhibited an efficient benefit in producing reinforced concrete members with high anti-corrosion property.4、A Finite Element model was established to analyze the bond property between reinforcement bar and concrete. After the pullout test, the numerical simulation was conducted by ANSYS. The influence of different additions of nano-clay was studied on the mechanical property of RC member. It was concluded that the bond deterioration of bond property between corroded concrete and steel bar should be considered in Finite Element analysis of the corroded concrete reinforcement structure.