Effect of repeated tensile load damage on chloride-ion transport properties in concrete

Concrete structures in marine environments often face durability problems owing to the coupled action of external loads and chloride-ion erosion. Therefore, in this study, we conducted chloride ion tests on damaged concrete at four tensile stress levels and three varying number of load cycles. The test results indicate that an increase in the tensile stress and number of load cycles results in a gradual increase in the concrete damage coefficient. At fewer cycles, 50% tensile stress was the critical threshold point of damage; the damage was evident beyond this range. As the number of cycles increased, the damage increased gradually up to the critical threshold and thereafter increased rapidly. With an increase in the tensile stress level, the diffusion coefficient of chloride ions increased gradually; the loading degree improved the permeability of chloride ions. In addition, based on the theory of linear fatigue cumulative damage to concrete, a mathematical model of the relationship between the load factor and concrete damage coefficient was established. Using this model, a prediction model for the chloride ion diffusion coefficient was proposed considering the tensile stress level, load cycle number, and other load factors.