Effect Of Sulfate Erosion On Interfacial Bond Behavior Of CFRP-concrete Under Different Stress Levels

Carbon fiber reinforced composite(CFRP)has many advantages such as light weight,high strength,good durability and convenient construction.CFRP reinforced concrete structure is through the bond stress between CFRP sheet and concrete to achieve the load transfer of the two materials,so that the synthesis of the two materials work together as a whole.Therefore,the mechanical properties of CFRP-concrete bond interface is the core of CFRP reinforced concrete technology.However,in practical projects,CFRP-reinforced concrete structures are often in a harsh environment,which will affect the bonding performance of the CFRP-concrete interface,and thus affect the strengthening effect of CFRP-reinforced concrete structures.At present,the research on the durability of the CFRP-concrete interface is not enough.In this paper,the sulfate dry-wet cycle and continuous load coupling are used to simulate the environmental erosion,and the degradation law and degradation mechanism of the mechanical properties of the CFRP-concrete interface under the sulfate environment are discussed.The main research contents and conclusions of this paper are as follows:(1)The influence of sulfate on the failure morphology,tensile strength,elastic mod ulus and elongation of CFRP sheet was studied through the tensile test of CFRP sheet under the coupled action of room temperature,sulfate dry-wet cycle and continuous load.The results show that the dry and wet cycle and continuous load of sulfate have little effect on the properties of CFRP sheet.(2)Double-sided shear test was used to conduct experimental research on the bonding interface performance of CFRP-concrete under room temperature,sulfate dry-wet cycle and continuous load coupling,and the variation rules of performance parameters such as failure mode,interface bearing capacity and stress and strain distribution of CFRP-concrete bonding interface were emphatically analyzed.The influence of concrete strength and continuous load level on the bond interface performance is also analyzed.The experimental results show that:(1)After the action of sulfate wet and dry cycle,the interface failure morphology gradually changed,with the increase of dry and wet cycle time,the interface failure from the bonding interface of the shallow layer of concrete damage gradually become bonding interface failure;(2)In the early stage of wet and dry cycle erosion,CFRP-concrete interface bearing capacity,interface stress and strain are slightly increased.However,with the increase of erosion time,all parameters began to decline,and the longer the erosion time,the greater the decline;(3)Change the concrete strength and continuous load level will affect the interface parameters,concrete strength will increase the value of the parameters,the load level will reduce the value of the parameters.(3)Based on the regression analysis of the change law of the interface bearing capacity with the erosion time,and the influence coefficient of the bearing capacity under the action of sulfate dry-wet cycle(considering the strength and load level of concrete),the CFRP-concrete interface bearing capacity model considering the action of sulfate dry-wet cycle was established.(4)Based on the regression analysis of the change law of the interface adhesion-slip curve,the expressions of the interface characteristic parameters(the peak value of the interface shear stress and its corresponding slip amount)and the interface ductility parameters were obtained.On this basis,the CFRP-concrete interface adhesion-slip model considering the action of the dry and wet cycle of sulfate was established.