Numerical Study On The Effect Of Chloride Salt Corrosion On The Mechanical Properties Of Concrete Members

In the study of concrete durability,the research on the effect of loading effect on the chloride salt erosion process and the change law of concrete mechanical properties after erosion has always been the top priority.A large number of scholars have conducted experimental research and numerical simulation analysis on this topic However,due to the inconsistency of environmental conditions,the comparability of many research results is weak,and most of the studies have focused on the study of chloride ion diffusion behavior in concrete under axial tensile stress.For shear stress and axial compressive stress The research below is slightly inadequate.This paper takes C30 concrete as the research object,quantitatively analyzes the chloride ion concentration in the concrete under shear and tensile(compressive)load effects and the uniaxial compressive strength value of the concrete after being eroded by the chloride salt through numerical simulation,and further draws different The variation law of chloride ion diffusion coefficient in concrete under load and the change trend of damage of concrete mechanical properties under the action of chloride salt corrosion.Specific research includes:(1)Based on the existing research results of the mechanical properties of the chloride.eroded concrete,based on Fick's second law,the chloride ion diffusion equation under the consideration of time effect,concrete curing ability,crack state and other factors was established.(2)Based on the COMSOL software,it is easy to deal with the problem of ion migration in solid matter under the coupling of multiple physical fields.A numerical simulation study on the diffusion process of chloride ions in concrete under tensile,compressive,and shear stress is carried out.The results show that the effect of axial tensile stress and shear stress is similar,and it is more significant to increase the diffusion rate of chloride ions in concrete.On the contrary,the effect of axial compressive stress makes the microscopic pores in the concrete decrease or even close,thereby delaying the migration of chloride ions and reducing the diffusion coefficient of chloride ions.On the other hand,the chloride ion diffusion coefficients are not much different under different loads under low stress levels,and the higher stress levels will cause the chloride ion diffusion coefficient to increase significantly.(3)The compressive strength of concrete under different chloride salt concentrations and different diffusion depths is discussed,and the damage rate is defined by the compressive strength change rate.It is found that as the erosion time increases,the concrete first exhibits negative damage(increase in strength)Subsequent damage(reduced strength)occurs,and the damage rate curve takes the form of a parabola.The correlation between the erosion time and the damage rate is obtained,and the change rule of the damage rate with time under the erosion environment of the chloride salt solution is obtained through data fitting.