Study On Axial Compression Performance Of RC Columns Strengthened By TRC Based On Impressed Current Cathodic Protection In Chloride Environment

Reinforced concrete columns,as the main bearing capacity of vertical load in the structure,and its durability in corrosive environment deserve attention.China has a long coastline and many saline alkali environments.When reinforced concrete(RC)columns are in chloride environment for a long time,the internal reinforcement of concrete is easy to suffer from the erosion of chloride ions from the outside,which leads to the corrosion of reinforcement and the expansion and cracking of protective layer concrete.This phenomenon is more serious under the action of dry and wet cycles such as tide and wave splash.The bearing capacity and deformation capacity of RC columns are reduced to some extent after being corroded by chloride.When encountering earthquake,corroded RC columns are prone to non ductile failure such as shear and bending shear,and even lead to overall collapse of the structure.Therefore,how to use effective anti chloride ion corrosion reinforcement method to effectively strengthen RC structure is the hot spot and urgent need of relevant research at present.Textile reinforced concrete(TRC)is a new type of fiber-reinforced composite material,which has the advantages of light weight,high strength,high temperature resistance and corrosion resistance.The application of TRC in the reinforcement of chloride environment structure can not only improve the mechanical properties of RC structure or components,but also prevent the structure from further chloride corrosion.However,the TRC reinforcement layer itself can not completely block the connection between the external corrosion environment and the internal environment of the structure.The strengthened structure or components may still suffer from chloride ion corrosion under the continuous corrosion environment,which requires that when the TRC is used for the reinforcement of corroded RC,it is necessary to assist a certain measure or method of chloride corrosion resistance to further protect the internal reinforcement of concrete to ensure that After reinforcement,the corrosion protection structure has better resistance to chloride ion corrosion.Impressed current cathodic protection(ICCP)is a very effectiveanti-corrosion technology recognized internationally.In order to improve the effectiveness and reliability of the reinforcement of corroded structures or components in chloride environment,it is very important to combine TRC with ICCP.In this paper,with the support of the National Natural Science Foundation of China "Research on the life cycle mechanical properties of fabric reinforced concrete formwork and its composite beams and slabs(51478408)" and "Research on the seismic performance and damage mechanism of RC columns damaged by bending and shearing considering the history of cyclic loading(51508154)",the research on the axial compression performance of RC columns strengthened by TRC in chloride environment based on impressed current cathodic protection was carried out The main research contents and conclusions are as follows:(1)Based on the axial compression test of 12 RC columns in chloride environment,the failure mode,cracking load,axial bearing capacity and deformation(or ductility)of RC columns with different design parameters,number of cycles and stirrup ratio under dry and wet cyclic corrosion were analyzed,and the degradation mechanism of the axial compression performance of RC columns in chloride environment was analyzed according to the test results.The results show that the bearing capacity and deformation performance of RC columns in chloride environment are decreased to some extent after cyclic wet and dry erosion,with the maximum decrease of 19.01% and 25.57%.The non ductile failure mode tends to be obvious with the increase of corrosion degree,and even brittle failure occurs in the corroded RC columns.The mechanical properties and failure modes of RC columns with lower stirrup ratio and smaller cross-section size are greatly affected by dry wet cyclic erosion.(2)Based on the study of the axial compression performance of 24 RC columns strengthened by TRC in chloride environment,the failure mode,cracking load,axial bearing capacity and deformation(or ductility)of RC columns strengthened by TRC with different design parameters(specimen size,reinforcement ratio and grid distribution ratio)under dry wet cyclic corrosion were analyzed,and the degradationmechanism of the axial compression performance of RC columns strengthened by TRC in chloride corrosion environment was studied according to the test results And the stress-strain relationship model of TRC confined RC columns considering the effect of chloride drying and wetting cycles is established.The results show that the axial compression performance of RC columns strengthened by TRC is improved obviously,and the more layers of fiber mesh in the reinforcement layer,the more obvious the reinforcement effect is,and the maximum bearing capacity and deformation performance of RC columns after reinforcement can be increased by30.76% and 31.08%;the degradation degree of axial compression performance of RC columns strengthened by TRC is significantly lower than that of unreinforced columns under chlorine salt dry wet cycle,but the bearing capacity and deformation still have a certain degree The loss shows that the corrosion of RC columns by chloride can not be completely prevented by TRC alone.The stress-strain relationship model of RC columns restrained by TRC considering the influence of chloride corrosion can be used to describe the constitutive relationship of RC columns strengthened by TRC in chloride environment.(3)Based on the research on the axial compression performance of RC columns strengthened by TRC in chloride environment,the axial compression performance of RC columns strengthened by TRC with different design parameters(protection potential,section size,stirrup ratio and grid ratio)under dry and wet cyclic corrosion is analyzed.Combined with the results of research content(2),the chloride resistance of RC columns strengthened by ICCP and TRC in chloride environment is compared and analyzed Sub erosive properties.The results show that the corrosion resistance of RC columns strengthened by TRC can be further improved by using ICCP technology in chloride environment.The corrosion rate of stirrups in the same number of dry and wet cycles is significantly lower than that only strengthened by TRC.The degradation degree of bearing capacity and deformation performance of reinforced columns is significantly reduced.The bearing capacity and deformation performance of RC columns strengthened by TRC are better than that of RC columns strengthened byTRC alone The maximum increase of columns is 24.97% and 37.23%,which is beneficial to the service life of RC columns in chloride environment.