Experimental Research On Chloride Ion Erosion Of Fatigue-damaged Concrete In Salt Spray Environment

Concrete bridges in coastal areas not only bear the cyclic load of the vehicle,but also suffered the erosion of chloride ions in the environment.The interaction of fatigue loading and chloride penetration will accelerate the deterioration of the performance of bridge structures,resulting in premature durability problems.From actual conditions,this paper focus on the effect of fatigue damage on chloride ion transport in concrete under salt spray environment.The main issues in this paper are as follows:(1)Concrete constant amplitude bending fatigue test is carried out,and the development regularity of concrete deformation and fatigue damage is analyzed.The ratio of residual strain to ultimate residual strain is defined as the damage extent.According to the results of this experiment,concrete fatigue damage evolution equation is deduced.(2)The water permeability of fatigue damage concrete is tested by Autoclam permeability tester.The results show that fatigue damage deteriorates the impermeability properties of the concrete and decrease its impermeability level.Damage variable 0.4 is the starting point of the sharp deterioration of concrete impermeability.(3)Using climate test box to simulate the coastal salt spray environment,salt spray corrosion test of fatigue damage concrete is carried out and the effect of fatigue damage on chloride ion transport in concrete is analyzed.The results revealed that fatigue damage deteriorates the performance of concrete to resist chloride ion corrosion,increases chloride ion contest and surface chloride concentrate of concrete and improves chloride diffusion coefficient.Damage variable 0.4 is the starting point of the sharp deterioration of the concrete resistance to chloride ion corrosion.Further research shows that there is a good linear correlation between the concrete chloride diffusion coefficient and water permeability coefficient.(4)Based on the Fick’s second law,a chloride diffusion model considering the effect of fatigue load is established and the model is demonstrated by laboratory tests.