Research On Corrosion Behavior And Protection Method Of Steel Bars In Sea Sand Concrete Structure In Atmospheric Environment

It is an inevitable trend for the future development of construction industry to utilize sea sand resources in coastal area in engineering construction.However,the corrosion of steel bars induced by chloride ions in sea sand is always a problem to be solved.The irregular use of sea sand may cause serious damage to the so called“sea-sand building”.In the atmospheric environment,it is necessary to consider factors such as concrete carbonization that lowers the p H value,release of solidified chloride ions,and chloride ion redistribution.This makes the behavior of steel corrosion in sea sand concrete with greater uncertainty.The synergistic effect of concrete carbonization and chloride ion corrosion is the main reason for the indefinite deterioration of sea sand concrete.Even when the chloride ion content introduced by sea sand is within the limits required by the specification,sea sand concrete may face lower durability than designed Risk of destruction.In addition,there is a lack of corresponding research on suppressing the corrosion of steel bars in sea sand concrete.In this paper,the research on the corrosion behavior of sea sand concrete reinforcement exposed in the atmospheric environment and the protection methods are carried out.The main conclusions are as follows:(1)Under the conditions of natural carbonization and rapid carbonization,the addition of chloride ions during mixing can improve the carbonation resistance of concrete.And when the chloride ion content is within a certain range,the higher the chloride ion content,the better the resistance to carbonization.The chloride ion introduced by sea sand can also improve the carbonation resistance of sea sand concrete.(2)After the concrete is carbonized,with the increase of time,the corrosion potential of steel bars in sea sand concrete tends to become negative,and the corrosion current density decreases.Judging from the corrosion current density,under rapid carbonization conditions,concrete carbonization and chloride ion corrosion have not yet shown a significant additive effect,which may be related to the loweroxygen content in the test environment.(3)Different pretreatment methods of steel bar surface have a certain effect on steel bar corrosion current density.Under the same working conditions,the corrosion current density of pre-rust treated steel bars is greater than that of the original and chemically treated steel bars.The corrosion current density of the steel bar gradually decreases with the increase of the steel bar protective layer,which also has a certain relationship with the thickness of the steel bar protective layer.(4)Comparing different conventional reinforcement methods,the corrosion potential and corrosion current density of reinforcement after CFRP reinforcement and epoxy resin reinforcement show a tendency to slow down corrosion,which has a positive effect on inhibiting corrosion of reinforcement in sea sand concrete.(5)Based on the assumption of the diffusion control of oxygen in concrete,a model for calculating the current density of corroded steel bars is proposed,and the influence of the protective layer thickness of the steel bar and the FRP external reinforcement method on reducing the corrosion current density of corroded steel bars is quantitatively analyzed.Based on the calculation and analysis results,a reinforcement design method for comprehensive load capacity restoration and durability degradation control is proposed.