Experimental Study On The Bonding Performance Between GFRP Bars And Concrete Under Erosion Environment

FRP bar is a new type of lightweight,high strength,electromagnetic fatigue resistance and corrosion resistance composite material,because of its good thermodynamic properties,is widely used in large span space buildings,bridge structures,offshore residential buildings,and some harsh natural environment.At the same time,FRP bar is also regarded as one of the good materials to replace steel,which is used to deal with the problem of structural aging due to the corrosion of steel.The interface between FRP bars and concrete has reliable bond performance,which is conducive to the wide application of FRP bars in civil engineering structures.With the development of China’s coastal construction and industrialization,higher requirements are put forward on whether the structure can work in some special environments.Based on the above background,the following studies are carried out in this paper:1.The mechanical properties of GFRP bars were tested,and the tensile strength and elastic modulus of GFRP bars were obtained.The compressive strength of seawater sand concrete and ordinary concrete were tested respectively,and the failure modes were observed,and the compressive strength in indoor environment and erosion environment were obtained,which laid the foundation for the subsequent test analysis.2.Experimental research was carried out on the bond performance of different types of concrete(seawater sand concrete,ordinary concrete)and GFRP bars.The influence of the key parameters,such as concrete type,reinforcement diameter,bonding length and reinforcement surface treatment,on the bonding performance of GFRP bars and concrete,was investigated through the center drawing test of 51 bond specimens in 17 groups.The test material,loading device and test process are described in detail,and the failure mode of the specimen is defined.The variation trend of bond strength between GFRP bars and concrete under different parameters is summarized and analyzed.Compared with ordinary concrete,the bond strength between seawater sand concrete and GFRP bars is good.Due to the uneven distribution of bond stress along the buried length,the bond strength between GFRP bars and concrete decreases with the increase of diameter and bond length.For the surface treatment form of reinforcement,the bond strength between shallow thread GFRP bars and concrete is greater than sand blasting GFRP bars and greater than winding GFRP bars.3.A comprehensive and in-depth analysis was carried out on the bond performance of GFRP bars and concrete in an erosion environment.Firstly,36 bond specimens in 18 groups were soaked in salt solution and alkali solution,and the center drawing test was done when the soaking period was reached.Secondly,the surface changes of the specimens after corrosion are analyzed from the macroscopic perspective,and the failure mechanism between the reinforcement and concrete is analyzed from the microscopic perspective.Secondly,based on the factors of bonding length and soaking time,the change of bonding strength between GFRP bars and concrete in corrosive environment was investigated,and the τ-s curve between GFRP bars and concrete in corrosive environment was drawn.Compared with salt environment,FRP bars and concrete are more sensitive to alkali environment,and the bond strength degrades more,and the bond strength decreases with the increase of bond length and soaking time.4.Based on the summary and test of the existing bond slip constitutive model,a bond slip constitutive model of GFRP bars and concrete is proposed,which is suitable for erosion environment.The concept is clear and fits well with the test results.In this paper,the test of bonding performance between GFRP bars and concrete is detailed and comprehensive,the analysis of test results is clear and profound,and the established research results have certain reference significance for related structural design.