Study On Interface Mechanism Between Composite Cement-based Materials And Concrete

Along with the urban renovation,the application of wire-cement based materials composite layer has been considered a suitable solution to strengthen concrete structures.However,the bond interface mechanism and the tensile properties of this composite layer are indeterminated.This paper is devoted to study the tensile performance and the bond mechanism of steel strand mesh-cement based composite layer.Specifically,the bond-slip characteristics of the interface between steel wire and cement-based material,the bond mechanism of interface between the composite layer and concrete and the tensile properties of composite layer are tested and analyzed respectively.Obtained results furnish the effect rules of the chopped steel fibers,PP fibers and bond length on the interface bond properties.The bond-slip model of the interface between the concrete and the composite layer is presented,and the influence of chopped fibers on the composite layer tensile properties is discussed.The following concluding remarks can be drawn:(1)Based on the pull-out test of the steel wire-polymer mortar specimens,it can be found that when the high-strength steel wire was pulled out,the mortar specimens were not appeared obvious damage.The failure mode of the steel wires by the interaction was characterized.Comparing the pulled-out force-relative displacement curves of three kinds of polymer mortars,the interaction of the bond interface between steel wires and polymer mortar was weakened by adding steel fibers and PP fibers.(2)Because of the different kinds of the composite layers,single shear tests on the interface between composite layer and concrete confirmed that the failure modes were cracking on mortar layer,tensile failure of steel wire,complete debond failure of composite layer and slip failure of steel wire.The bond area of the composite layer with short PP fibers had a great influence on the bond force of the interface,but it had little effect on the bond stress.Meanwhile,based on the existing formulas,a bond-slip model suitable for the interface between composite layer and concrete in this test was obtained,aiming to provide reference for the reinforcement design.(3)The axial tension tests of the composite layer confirmed that the failure mode of the composite layer under was mainly the tensile failure.The ultimate tensile force of the composite layer was increased by 12.51% for adding PP fiber,and 16.43% for adding steel fiber.The tensile stiffness of the composite layer at the non-cracking stage was greatly affected by the types of fibers.The addition of PP fibers and steel fibers can increase 13.36% and 23.06% respectively.However,the tensile strength of the composite layer during the cracked failure stage was the tensile stiffness of the steel wire,which is not affected by the type of fibers.