Experiment And Mesoscopic Numerical Simulation Of Chloride Ion Transmission In Concrete

Reinforcement corrosion is the main reason that leads to the decrease of durability of concrete structure.Especially in marine and deicing salt environment,the corrosion of reinforcement is common due to chloride ion erosion,which leads to cracking of concrete.At the mesoscopic level,concrete is a complex and inhomogeneous composite material.Moreover,in actual engineering environment,the corrosion of chloride ion to concrete structure is affected by many factors and the presence of load effect also affects the transfer of chloride ion in concrete.Therefore,it is of great theoretical significance and engineering application value to study the erosion effect of chloride ions on concrete from macro and meso scales.Supported by the National Natural Science Foundation of China(No.51509084),this paper researched the transmission of chloride ion in concrete from macro and meso scales through a combination of theory,experiment,and numerical simulation.The effects of different coarse aggregate content,water-binder ratio,and porosity on the transmission of chloride ions in concrete were analyzed through a rapid chloride ion migration test and mercury injection test.Then analyzed the influence of mesoscopic parameters and different influencing factors on chloride ion transfer by programming the concrete mesoscopic random aggregate model and establishing the chloride ion transfer model under multifactor actions.Finally,the law of chloride ion transmission in concrete under load was studied.The main research contents were as follows:(1)Through RCM test,the influence of different coarse aggregate content and waterbinder ratio on the diffusion property of chloride ion in concrete was studied,and through mercury injection test,the relationship between the microstructure characteristics of concrete with different water-binder ratio and chloride ion permeability in concrete was obtained.(2)The program of MATLAB software is used to establish the concrete mesoscopic random aggregate model,and the validity of the mesoscopic finite element model was verified by experiments.The influence of mesoscopic parameters such as coarse aggregate distribution,model dimension,coarse aggregate content and interfacial region characteristics on chloride ion diffusion was analyzed.(3)A chloride ion transport model was established which comprehensively considered the influences of water cement ratio,time,binding effect,temperature,relative humidity and concrete deterioration.To verify the effectiveness of the established chloride ion transport model and numerical analysis method under the multifactor actions by numerical analysis of long-term exposure test of Marine concrete.The chloride ion transport model and random aggregate model established in this paper were used to analyze the influence of water cement ratio,binding effect,temperature,relative humidity and concrete deterioration on the chloride ion transport.(4)Based on the established chloride ion transport model under load,the chloride ion erosion test in concrete under bending load was numerically analyzed to verify the validity of the model.The effects of different stress states and stress levels,concrete porosity and elastic modulus on chloride ion transmission were analyzed.