Chloride Ion Transport in Concrete of Ballastless Track under Fatigue Loading

The chloride ion penetration resistance of concrete structure of ballastless track under fatigue load is one of the main factors affecting its service performance. In order to analyze the variation of chloride ion transport in concrete under fatigue load, the bending fatigue loading test of concrete specimens immersed in chloride solution was carried out. A two-field coupling model based on the structural mechanics field and the chloride transport field was then established with COMSOL finite element software to simulate the chloride diffusion behavior in concrete. The results show that when the erosion time is 2 d, the chloride ion diffusion depths corresponding to the stress levels of 0.3, 0.5, and 0.7 are 7, 11 and 16 mm, respectively, which indicates that the chloride diffusion depth in concrete increases with an increase in fatigue stress level. The chloride ion concentration calculated by the two-field coupling finite element model is basically consistent with the experimental test results, which proves that the model is reasonable. What’s more, the diffusion depth of chloride in concrete increases with the erosion time, and the relationship between them can be described well by a unary quadratic polynomial.