Bonding Behaviors Of Ultra High Performance Concrete And Reinforced Concrete

Ultra-high performance concrete(UHPC)has the super high strength and super durability.Bridge reinforcement with UHPC can achieve significant improvements in bearing capacity and durability.In the engineering and academic circles,materials and technologies research on bridge reinforcement with UHPC has aroused widespread concern.However,this research has just started,there are still many problems to be solved,such as theory,technology,materials,structures and so on.The keypoint problems focused on the interfacial bonding between UHPC and the reinforced structure,which has important significance for ensuring reinforcement effect and durability.In this paper,the interface properties of UHPC and normal concrete(NC)were studied.Based on the technical route combining theoretical analysis and model test,the research on NC substrate damage properties,UHPC-NC bonding shear properties,bonding tensile properties,UHPC-NC bonding shrinkage properties were studied.Firstly,the UHPC material properties and NC substrate damage properties were studied.The UHPC material parameters were obtained by UHPC strength test,elastic modulus mechanics test and free shrinkage test.By designing the NC substrate damage specimens with the grooving interface,the NC substrate damage test was carried out.And the influence of the grooving on the NC substrate was revealed.Then,the bonding mechanical properties of UHPC-NC were studied.UHPC-NC direct shear test and bending test were carried out by having designed UHPC-NC bonded specimens with grooving interface and paste interface.The influence of the interface treatment method,grooving shape and arrangement on the UHPC-NC interface were revealed.And the reasonable interface treatment techniques were given.At the same time,the failure mode of the bonding interface,the relationship between the UHPC-NC bonding strength and the damage degree of the substrate,the shear bond-slip relationship of the interface were gained.Also the bonding properties of UHPC-NC were proved.Finally,the ANSYS finite element model of interfacial bonding was studied.Based on the equivalent temperature difference method and the interface bond-slip relationship,the UHPC-NC restrained shrinkage model and the UHPC-NC bond-slip model were established respectively.The stress distribution of UHPC-NC bonding interface in different interfacial treatment was obtained,which showed that a low risk of shrinkage cracking on bonding interface.The model is accurate.The research results in this paper can provide theoretical and technical references for reinforcing deteriorative NC bridge by UHPC.