| In recent years,rail transit construction projects represented by the subway are in full swing,and high-latitude regions such as the Northeast and North China have become hot spots for subway construction.Concrete is widely used in the construction of subway projects because of its wide source,low cost,and easy access.However,unlike conventional buildings and conventional environments,in the service process of subway lines in high latitudes,concrete often breaks prematurely under the action of freeze-thaw cycles and stray currents.Therefore,it is of great significance and value to carry out research on the durability of concrete under the action of freeze-thaw cycles and stray currents to maintain the operating capacity of subway projects.The main research work and results of this article include the following aspects:1.This paper analyzes and summarizes the destruction mechanism of concrete under the action of freeze-thaw cycles.Combined with Faraday’s first law of electrolysis,the destruction mechanism of concrete under the effect of stray current and the calculation method of steel corrosion amount are determined;the material parameters are determined as the basic Variable thinking of concrete durability research of subway engineering.2.Based on the randomness of the change of material parameters,according to the relevant theories and experimental models at home and abroad,a random method is adopted to investigate the change law of the freeze-thaw service life of concrete under the random change of material parameters.The results show that when other parameters remain unchanged,the greater the water-binder ratio,the worse the frost resistance of the concrete and the shorter the service life.When the water-binder ratio increases from 0.35 to 0.40,the freeze-thaw service life of concrete in the northeast and northwest regions decreases by37.5%;the north China region decreases by 42.9%.The water-binder ratio has a significant effect on the freeze-thaw service life of subway engineering concrete.Under the condition that other parameters remain unchanged,when the gas content is in the range of 4% to 6.5%,increasing the gas content can increase the freeze-thaw service life of the concrete,and the gas content has a significant effect on the freeze-thaw service life.When other parameters remain unchanged,when the fly ash content changes in the range of 18% ～ 32%,the freeze-thaw service life of concrete decreases with the increase of the content,but compared to the water-binder ratio and gas content,its effect on freeze-thaw The impact of service life is not significant.Based on the model established in this paper and the distribution rules of various parameters,the freeze-thaw service life of the subway engineering concrete in the three north areas(North China,Northeast,Northwest)has been calculated to reach 194.5,107.8,and 109.6 years respectively,meeting the freeze-thaw durability requirements of the project.3.The stray current corrosion concrete test was carried out,and the time-varying relationship between the concrete corrosion current and the accumulated electricity was selected for regular analysis;the test results showed that: without the addition of admixtures,the corrosion rate of the concrete is very fast,and the corrosion current increases rapidly,The cumulative electricity consumption shows a linear growth trend under the rapid increase of corrosion current;after adding admixtures,the corrosion of concrete can be divided into three stages: early active ion diffusion stage,mid-term corrosion products and crack generation and expansion stage,The final stage of destruction.4.The test results show that the corrosion rate of concrete under the effect of stray current is affected by factors such as the type,content and proportion of admixture.The addition of admixture can make the concrete destruction time under stray current at least double.In the case of single admixture,different admixtures have a similar effect on the corrosion law of concrete under the effect of stray current;under the same admixture ratio,the effect of slag to inhibit the corrosion of concrete under the effect of stray current is better than fly ash.In the case of double admixture,with the increase of the total admixture,the corrosion resistance of concrete to the effect of stray current is significantly improved.Comparing the cumulative electricity flow rate and corrosion rate of concrete with different mixing ratios under damage,it is found that under the effect of stray current,the cumulative electricity flow rate of concrete damage is generally around 30,000 coulombs,and the corrosion rate is between 3% and 4%.Taking the accumulated electricity and corrosion rate at the time of concrete failure as the main indicators,taking into account the corrosion rate and the fluctuation of corrosion current,it is considered comprehensively that,based on the mix ratio design of this paper,25% fly ash and 25% slag are the best Mix ratio. 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