Reinforced Concrete Under Freeze-Thaw-Chlorideion Coupling Study Of Interfacial Bond Strength

Reinforcing steel and concrete are two materials with different mechanical properties.A good synergy between reinforcing steel and concrete is a basic prerequisite to ensure that reinforced concrete structures have adequate safety performance.When reinforced concrete（RC）is subjected to freeze-thaw cycles and chloride ion attack,the reinforcement in the concrete will gradually corrode over the years,resulting in a reduction in the bonding properties between the reinforcement and the concrete,which will have a significant impact on the normal performance and load-bearing capacity of reinforced concrete structural members.Therefore,it is important to study the bond slip properties of the reinforcement-concrete interface under the combined effect of freeze-thaw cycles and chloride ions.Most of the existing results are focused on the bond performance of reinforcement and concrete under the action of chloride ions alone,but less research has been conducted on the coupled freeze-thaw-chloride ion environment,where the deterioration of the concrete protective layer is accelerated,leading to accelerated chloride ion erosion and further accelerated corrosion of the reinforcement.In view of this,this paper,based on existing research,combines theoretical analysis and numerical simulation to investigate the bond-slip performance of the reinforcement-concrete interface under the coupled freeze-thaw-chloride ion effect.（1）a large number of domestic and international studies have been collated and analysed to systematically summarise the mechanisms of structural deterioration of concrete under freeze-thaw cycles and corrosion of reinforcement under the action of chloride ions,and based on previous studies on the degradation of mechanical properties of rusted reinforcement,an intrinsic model of bond-slip at the reinforcement-concrete interface based on the action of different conditions has been collated.At the same time,the diffusion process of chloride ions and the corrosion process of reinforcement under the action of chloride ions are comprehensively analysed and discussed,and a model for the area loss of rusted reinforcement under the action of chloride ions is proposed,which provides the foundation support for the refined analysis in the subsequent chapters.（2）In order to obtain the bond-slip model of reinforced concrete under freeze-thaw-chloride ion coupling,based on the cross-sectional area of rusted reinforcement under chloride ion action,the expression of chloride ion diffusion coefficient under freeze-thaw cycling is analysed and fitted according to the collation of different existing test data,and the cross-sectional area of rusted reinforcement under freeze-thaw-chloride ion coupling is obtained by combining the initial time of reinforcement corrosion,and the freeze-thaw-chloride ion coupling is introduced.The remaining ratio of the cross-sectional area of reinforcement under the coupling action of chloride ions is also introduced,while the bond-slip calculation formula for the reinforcement-concrete interface under the coupling action of freeze-thaw-chloride ions is established on the basis of the bond-slip formula for rusted reinforcement based on China’s Concrete Structural Design Code.（3）In order to realize the finite element modeling of reinforced concrete based on the coupling effect of both,this paper uses ABAQUS computational analysis software to create the numerical analysis model of the drawing specimen,and establishes the freeze-thaw-chloride ion coupling based on the material ontological relationship between reinforcement and concrete,as well as the freeze-thaw-chloride ion coupling effect of reinforcement-concrete interface bond-slip ontological model established in this paper.The finite element model of bond-slip of reinforced concrete under the coupling effect of freeze-thaw-chloride ions was established.The applicability and reliability of the numerical simulations are verified,and the results can be used as a reference for the study of the bonding performance of reinforced concrete under the coupling effect of freeze-thaw-chloride ions.