Study On The Effect Of Electric Field Intensity On Chloride Binding Capacity Of Concrete

A large number of engineering practices have proved that the corrosion of steel bars is the main reason that affects the durability of the reinforced concrete structure.Among them,corrosion of steel bars caused by chloride ions is the most serious and common.After the chloride ions penetrate the concrete,most of them will be bound by the hydration products of the cement-based material in the form of physical adsorption or chemical bound.And this kind of bound chloride will not damage the structure.However,after the corrosion of steel bars caused by free chloride,the corrosion electric field is formed in the concrete,which coexists with the macrocell and microcell of corrosion.In this corrosion electric field,the bound chloride will be released,the content of free chloride will increase,which aggravates the corrosion of steel bars.Therefore,it is very important to determine the effect of corrosion electric field intensity on chloride binding capacity for protecting the concrete structure and establishing an accurate chloride ion migration model.The main research content and results of this paper are as follows:(1)The pros and cons of the chemical titration method and the chloride ion concentration meter in measuring the content of free chloride ion were compared,and finally the chemical titration method was adopted as the method for determining the content of chloride ion in this experiment.In addition,for the acid-soluble and water-soluble methods,a method to reduce test errors was provided from the perspective of analytical chemistry.(2)From the perspectives of the corrosion current density and the initial sodium chloride content,the change of chloride binding capacity in concrete under the action of corrosion electric field was discussed,and the Langmuir nonlinear adsorption curve was used to fit the experimental data.The research results showed that the chloride binding capacity is continuously weakened with the increase of the corrosion current.And the initial concentration of sodium chloride has no obvious effect on the chloride binding capacity under the corrosion electric field.Besides,the parameter of chloride binding capacity in concrete was introduced,and the experimental data showed that the parameter of chloride binding capacity could reflect the change of chloride binding ability under the action of corrosion electric field.(3)A method that can distinguish between physical adsorption and chemical bound chloride in concrete was used to study the changes in the content of physically adsorbed chloride and chemically bound chloride in a corrosion electric field.The experimental results showed that under the action of corrosion electric field,the content of physically adsorbed chloride in the concrete was reduced to a minimum.And the content of chemically bound chloride was also decreased to varying degrees with the increase of corrosion current.The reason may be that the decrease of alkalinity inside concrete caused the decomposition of chemically bound chloride.