Corrosion Damage Mechamism Of Reinforced Concrete Structures Caused By The Stray Current Of Rail Transit System

Rapid development of the rail transit is the major strategic needs of our country.Rail transit can effectively ease traffic pressure with the advantages of large transport capacity and high speed and energy saving etc.Compared with the general reinforced concrete structure,the rail traffic has higher requirements.The modern electrified train generally uses the rail as the power supply return circuit.As the insulation performance between the rail and the substructure becomes worse,a part of the power supply backflow will leak from the rail and form stray current(SC).New problems have been caused by rail transit,stray current corrosion damage(SCCD)has a serious threat to the safety of critical infrastructure.Aiming at the harsh reality of steel-concrete mixed structure and stray current corrosion in rail transit,in this paper,stray current corrosion mechanism,corrosion evolution law is studied with a combination of theoretical research and experimental verification.Finally,from the durability level,the basic theory,practical methods and core technology for the rail traffic safety operation are achieved.SC corrosion is different from natural corrosion,the current flows into the steel-concrete structure and acts as a corrosive agent to the reinforcement..Based on the electrochemical kinetics of corrosion,the mechanism of SC corrosion was discussed.The damage law of steel bar in simulated concrete under the coupling of SC and chlorine was studied.In this paper,the polarization curves of the anode and cathode regions of the steel are measured by Potentiodynamic scan(PDS).It is found that the corrosion of the steel surface undergoes the passivation state-active state.Chloride and SC with the role,the broken electrode electrode electrode will reduce the broken potential.So that steel into the early corrosion state.In the cathode region,the oxygen electrode reaction occurs first on the surface of the steel bar.With the increase of the potential of the electrode,the hydrogen evolution occurs,and the generation of hydrogen may cause the hydrogen embrittlement of the steel bar to fail and reduce the safe service life of the structureThe evolution mechanism of particle swarm in concrete porous media under the action of stray electric field and the interaction mechanism between SC corrosion and environmental particle swarm evolution.In this paper,the evolution and evolution of particle swell in concrete pore are studied by Inductive Coupled Plasma(ICP).It was found that the anions in the pore of the concrete moved to the anode under the action of the electric field,the cation moved to the cathode.Under the action of anodic electric field,the chloride ion moves toward the anode electrode and the chloride ion concentration,and the passivation film on the surface of the steel bar is destroyed,which makes the reinforcement enter the active state early.Under the action of the cathodic electric field,the sodium ions and potassium ions in the pore pore solution move toward the cathode electrode,and the SC leads to the formation of a soluble alkali silicate or aluminate with the interface between the reinforcement and the concrete,reducing the interface between the concrete and the steel The cohesive force further causes changes in the pore structure of the concrete.The contents of Calcium Hydroxide(CH)in concrete were studied by thermogravimetric analysis(TG or TGA)and X-ray diffraction(XRD).The results showed that the content of Calcium Hydroxide(CH)had not changed significantly.The microscopic changes of concrete pore structure under the action of nitrogen isothermal adsorption(Brunauer Emmett and Teller,BET)were studied.It was found that the porosity of concrete increased under strong electric field.