Three Dimensional Mesoscopic Numerical Simulation Of Chloride Diffusion In Reinforced Concrete

In the marine environment,the chloride eroding concrete structure causes the corrosion of concrete.It is not uncommon the deterioration of the bearing capacity or even the destruction of the concrete structure.The chloride intrusion problem has become a hotspot in concrete durability analysis.It is a long and slow process of the chloride ion diffusion in concrete.At present,the research methods on chloride diffusion in concrete are physical model experiment and numerical simulation.The physical model test period is long,and will consume a lot of time and effort.Furthermore,it is difficult to study the meso structure and properties of the concrete.While numerical simulation can not only simulate long-term chloride diffusion,but also can study the mesoscopic characteristics of concrete,which is a quick and effective method.More and more scholars have studied the chloride ion diffusion in concrete by numerical simulation.The meso-features of concrete mainly include cement mortar,coarse aggregate and interface transition zone.The properties of each part may have a great impact on the diffusion of chloride ion in concrete.In order to study the characteristics and properties of mass transfer in concrete,this paper focuses on the diffusion process of chloride ions in reinforced concrete at meso-level.The three-dimensional spherical random aggregate model is developed,and based on the model establish the method of meso-scale numerical simulation for chloride diffusion in concrete,study the effects of interface transition zone,volume fraction of coarse aggregate,rebar retardation effect and load on chloride diffusion with numerical simulation means.The aim of this study is to explore the diffusion of chloride ions in concrete,providing the basis for practical engineering applications.The main contents of this paper are as follows:1.This paper summarizes the research results of corrosion of steel bar and chloride ion transport in concrete,and combs out the basic model of chloride ion diffusion in concrete.Through integration,comparison and analysis,propose the selected chloride ion diffusion model of this paper.2.The three-dimensional random aggregate model of concrete is established by MATLAB.The model takes into account of randomness of aggregate size and distribution in aggregate,which is closer to the real situation.Based on this model,the diffusion of chloride ions in concrete was simulated by the COMSOL software.Compare the numerical results with the experimental results,and the results were in good agreement with each other to verify the reliability of the model.3.Study the influence of mesoscopic factors on the diffusion of chloride ions by the numerical simulation of chloride ion diffusion in concrete based on the three-dimensional spherical random aggregate model.And conclude the influence of interface transition zone and coarse aggregate volume fraction on chloride diffusion in Concrete.4.Based on the three-dimensional spherical random aggregate model of plain concrete,three-dimensional random aggregate model of reinforced concrete is established.Study the effect of steel bar on diffusion of chloride ions.And explore the effects of protective layer thickness,rebar diameter,rebar spacing on the rebar retardation effect.5.The effect of load on the diffusion of chloride ions is studied before and after the concrete is cracked.Calculate the volume strain of concrete under load before the concrete is cracked.The influence of load on the chloride diffusion coefficient is obtained according to the relationship between volume strain and diffusion coefficient.After the concrete is cracked,present the calculation method of crack width under load,and study the influence of different crack width on chloride diffusion.