Experimental Study On Interfacial Bonding Performance Of Reactive Powder Concrete Strengthened With Bar Mesh

The parallel development of new construction,maintenance,reinforcement and reconstruction has become the development trend of the industry in the new era.Improving the mechanical properties and durability of reinforced concrete structures is an important topic in the new era.Technical for strengthening concrete structures with reactive powder concrete and bar mesh(RPCBM)is a new,effective and comprehensive strengthening technology.Good bonding of the reinforced interface ensures the safety and durability of the reinforced structure.The bonding performance of RPCBM-OC is the most basic and critical problem in the theoretical research of RPCBM and Ordinary concrete(OC)composite structure.In this paper,based on the pull-off test and double shear test,the interfacial bonding properties of OC specimens strengthened with RPCBM are systematically discussed,and the results are as follows:(1)54 sets of pull-off tests were designed to explore the influence of concrete strength,core column diameter,interface roughness and bar mesh specification on the pull-off performance of RPCBM-OC interface,and the core column pull-off strength and failure mode were recorded.The structure shows that,in a certain range,the strength and roughness of concrete are positively correlated with the pull-out strength of the bonding interface.The diameter of the core column is negatively correlated with the drawing strength of the drill core,and the drawing strength of the core column with a diameter of 50 mm reaches the peak value.The denser the bar mesh specification,the higher the drawing strength of the drill core,but when the diameter of the core column is close to the bar mesh specification,the data dispersion is larger.(2)Twenty-seven sets of double shear tests were designed to explore the effects of interface roughness,steel bar planting rate and bar mesh specifications on the double shear performance of RPCBM-OC interface,and the shear strength,failure mode and load-displacement curve of each specimen were recorded.The results show that the shear strength and ductility of the reinforced interface are greatly improved after the concrete structure is strengthened by RPCBM,and it has good bonding performance.In a certain range,moderate roughness and the rate of planting steel bars are positively correlated with the interface shear strength;The specification of bar mesh is an important factor to improve the interface ductility.(3)Single-factor and double-factor analysis is carried out on the pull-off test data.The results show that the concrete strength grade,core column diameter and interface roughness have significant influence on the pull-off strength of RPCBM-OC interface at the level of 0.05,while the bar mesh specification has no significant influence on the test results.Two-factor analysis of the combination of bar mesh specifications and other factors shows that the interaction between concrete strength grade,interface roughness and bar mesh specifications has no significant influence on the test results,but the interaction between core column diameter and bar mesh specifications has significant influence on the test results.(4)For the double shear test data,single and double factors and linear regression analysis are carried out.The results show that the interface roughness and the rate of planting steel bars have a significant impact on the shear strength of RPCBM-OC interface at the level of 0.05,and the bar mesh specifications have a significant impact on the test results at the level of 0.1.Two-factor analysis of bar mesh specifications and other factors shows that the interaction between interface roughness,steel bar planting rate and bar mesh specifications has no significant influence on the test results.Roughness is the most influential factor on shear strength,followed by steel bar planting rate,and the specification of bar mesh is the weakest.The planting rate of steel bars and the specification of bar mesh have obvious influence on ductility.(5)In order to better calculate the interface bond strength of concrete strengthened with RPCBM,this paper establishes a model of bond interface shear strength based on experimental data,and puts forward a formula for comprehensively calculating the interface shear strength of ordinary concrete strengthened with RPCBM.The relationship between shear strength and moderate roughness is a power function,but when the roughness exceeds the limit,the shear strength begins to decrease;There is a linear function relationship between shear strength and the appropriate rate of planting steel bars,and the rate of planting steel bars ensures the upper limit of shear strength.Bar mesh ensures the contribution rate of friction and pin action.The experimental results are in good agreement with the theoretical analysis.