Study On Deterioration Characteristics Of Reinforced Concrete In The Persence Of Stray Current And Chloride Ion

With the rapid development of urban transit system, stray current inducedcorrosion in subway has attracted much attention. Concrete structures of the subwayengineering are typically exposed to aggressive environment where stray current andchloride ions coexist. Either of the two factors is capable of accelerating thereinforcement corrosion, thus generating cracks and undermining mechanicalperformance. The combine effect of stray current and chloride ions on reinforcementcorrosion is not a simple superposition, but a mutual-enhancing process, making thedegrading mechanism more complex. This paper is organized into three sections,based on a systematic study on the limit concentration of chloride ions, characteristicsof reinforcement corrosion and PHysical and mechanical properties of concrete in thepresence of stray current and chloride ions. Main results were briefly given asfollows:The first section examined the variation of the limit concentration of chlorideions with and without stray current, investigated the relationship between surfacechloride ions concentration and the breakdown potential upon passive film damagewhen different intensities of stray current, and proposed a method to indicate the limitconcentration of chloride ions:[Cl^-]/[OH^-]=2.33e^-0.12AIn the formula: A—Current intensity, mA.The second section discussed the variation of electrochemical parameters withinconcrete when exposed to this aggressive environment, and the effect of mineraladmixtures on reinforcement corrosion was clarified: the incorporation of fly ash (FA)and slag powder (SL) could substantially mitigate stray current induced corrosion; thecurrent density and the extent of corrosion were decreased with more FA and SLpresent and SL was more effective than FA.The third section presented the changes in compressive strength and elastic modulus of concrete and results indicated that addition of mineral admixtureeffectively restrained the degradation of mechanical performance and SL was moreeffective due to its more active pozzolana reaction. The degrading mechanism ofconcrete mechanical performance was also clarified and the relationship between thedegrading mechanical performance after corrosion and the intensity of stray currentand concentration of chloride ions was established.The research results of this paper will promote the design of undergroundengineering, underpins the key technology of urban subway engineering, and bearsgreat significance in the advancement of science, technology and economy in ourcountry.