Research Of Steel Corrosion In Concrete Under The Coupling Actions Of Stray Currents And Chloride Ion

With the accelerating urbanization, subways and light rails gradually become the most effective transportation to relieve the modern urban traffic pressure . But the subway stray current easily causes rebar of the major structure serious corrosion to threaten subway engineering safety and durability greatly. Hence, with the stray current corrosion phenomena becoming more common, scientific and technical workers and government departments at home and abroad have attached great importance to the reinforced concrete corrosion problem of subway major structure increasingly. Aiming to stray current corrosion problems of metro concrete major structure, The paper, which is supported by the Major State Basic Research Development Program of China (National 973 Project) project- the modern concrete failure mechanism of chemical-mechanical coupling damage under the action of in multiple factors (Project Numbers: 2009CB623203),did theoretical and experimental research on such three main aspects: effect of Stray current on transport properties of chlorine ion,reinforced electrochemical corrosion features under coupling action between stray electric current and chloride ions and its effect on the bending fatigue behavior of the reinforced concrete beam. The main conclusions are as follows:(1) Stray current improved migration velocity of chloride ion moving to inner concrete and surface of reinforced bar obviously , moreover, the stray current intensity becomes strengthened and the action time gets longer , the migration velocity of chloride ion moving to inner concrete and surface of reinforced bar becomes lager. Compared with natural conditions, the experiment data indicates that the chloride ion diffusion coefficient under the condition of stray current existence can increase 15.2%～44.3%。(2) Different from the rebar electrochemical corrosion triggered by chloride ion, the feature of rebar electrochemical corrosion triggered by stray current appeared stronger and rebar corrosion velocity increased obviously. Coupling between chloride ion and stray current further accelerates the corrosion progress of rebar and crack of concrete cover, then concrete strength degenerate seriously. (3) Damage variables defined by ultrasonic velocity ,with explicit physical significance,can effectively track the fatigue. The damage variable tracked display that the damage process of the RC beams under the simultaneous actions of stray current and fatigue load is similar to the fatigue damage process of them under general atmospheric environment and can basically be divided into three phases,but the development speed is faster. Especially when stray currents and chloride ion interaction, the reason is mainly caused by chloride ion and the stray current corrosion of steel bar corrosion and fatigue loading form the fatigue effects.