Study On Durability Of Anticorrosive Coating For Concrete Guardrail Of Expressway Bridge In Cold Region

The use of snow melting agent in many highways in northern China will cause the early damage of the concrete component root.As one of the most effective and economical methods to control the corrosion of concrete members and extend the durability of concrete components,concrete coating protection has been widely used in engineering.Therefore,the corrosion resistance and durability of concrete coating has become a concern of manufacturers and engineering units.The factors influencing the anticorrosion performance of the coating are analyzed by finite element analysis.By mathematical model method,taking epoxy coating as an example,the factors affecting the durability of epoxy coating are analyzed,and the service life of epoxy coating under certain environment is predicted.The specific work is as follows:（1）Through the study of the mechanism of anti-corrosion of concrete coating,the concrete coating is divided into two types.The factors affecting the anticorrosion performance of the coating were determined by exploring the failure of the coating.Based on the chloride ion diffusion model,the simulation model of chloride ion resistance of concrete guard bar coating of highway bridges was established by COMSOL software.The results show that the concrete coating can greatly reduce the chloride ion concentration in the guardrail and promote the durability of the guardrail;When the thickness and environment of different coatings are the same,the smaller the diffusion coefficient is,the better the protective effect is;With the increase of the thickness of concrete coating,the chloride concentration in the guardrail decreases greatly,and the decreasing trend gradually slows down;For the typical permeable coating cement-based permeable crystalline coating,with the increase of relative humidity,the chloride ion concentration in the guardrail gradually decreases,and the decreasing trend gradually increases.When the temperature changes between 261.9 K and 299.6 K,the chloride ion concentration in the guardrail gradually decreases with the increase of temperature.（2）Through the investigation of the failure forms of the coating,the mechanism of the coating failure is analyzed,the factors affecting the durability of the coating are determined.The regression model of service life of cement concrete coating is established by combining the influencing factors with Cox proportional risk regression model.The application of the mathematical model of life prediction is carried out by using SPSS software to verify the reliability of the model.Results show that,under the environment that the relative humidity is 69%,temperature is21℃,irradiation is 4,704.84 MJ/m²·a,chloride ion concentration is 0 mol/L,coating is carried out twice,the cement concrete water cement ratio is 0.5,and the coating is free of physical damage,the epoxy coating will obviously decline at the33^rd month.Prediction shows that the service life of this coating is around 42 months under the aforesaid environment.The model’s prediction results show a good agreement with the experimental research results.