Study On Bonding Properties Of Basalt Fiber Reinforced Polymer And Ultra-High Performance Concrete

With the rapid development of the construction industry,construction projects continue to develop towards diversification,large span and high durability.However,in traditional concrete structures,steel corrosion and concrete cracking are common,especially in harsh erosion environments such as marine and salt freeze,which brings hidden dangers to the service capacity and safety of construction projects.In recent years,basalt fiber reinforced polymer rib(BFRP),as a new type of FRP composite bar,has the advantages of light weight,high strength and corrosion resistance,and has been gradually applied to roads,bridges and marine projects.As a representative of high-strength and high-durability materials,ultrahigh-performance concrete has a dense microstructure and a very low permeability coefficient,which can not only effectively hinder the penetration of external erosion media,but also enhance the bonding strength between the matrix and BFRP ribs,so as to give full play to the excellent performance of BFRP ribs.Therefore,the use of BFRP-UHPC material system is of great significance to improve the long-term durability of construction projects and extend the life of concrete structures.The tight bonding of BFRP ribs and UHPC is the basis for the synergy between the two,and studying the bonding performance is crucial for the successful application of BFRP ribs to UHPC.Therefore,the central drawing test was used to test the bonding performance of BFRP-UHPC specimens under different working conditions,and the effects of BFRP rib diameter,fiber type,fiber content and other factors on its bonding strength were discussed.Based on the experimental data,a bond-slip constitutive model was established,and a series of explorations were carried out on each stage of the model,in order to provide technical support and literature reference for engineering practice.The main contents of the study are as follows:(1)The interface bonding performance of BFRP ribs and UHPC was studied,the influence of different factors on their bonding strength was discussed,and the bond-slip curve characteristics under different working conditions were analyzed.The results show that with the increase of fiber content,the bonding strength of BFRP-UHPC specimens shows a trend of increasing first and then decreasing.Compared with single fiber,the synergistic effect of steel-PVA hybrid fiber significantly improves the bonding performance of the specimen,and steel fiber has better improvement effect than PVA fiber in the hybrid fiber.The bond-slip curve of BFRP-UHPC specimens includes micro-slip section,slip section,stress reduction section and stress residual section.(2)Based on the failure mode of BFRP rib-UHPC specimens,the bonding failure mechanism was revealed.The results show that the failure modes of BFRP-UHPC specimens include BFRP rib pull-out failure,tensile failure and concrete cone failure.The damage interface of BFRP rib pull-out failure appears on the surface of the reinforcement,the damage interface of BFRP rib pull failure appears inside the reinforcement,and the damage interface of concrete cone failure appears on the surface layer of concrete near the loading end.(3)The bond-slip constitutive model of BFRP ribs and UHPC was established,and the experimental data were compared and analyzed with the curves of each stage(micro-slip section,slip section,stress reduction section,stress residual section)in the model,and the results showed that the established bond-slip constitutive model had high applicability.(4)The gray wolf algorithm is used to optimize the support vector regression model,and the prediction model of the interface bonding strength between FRP ribs and concrete is established,and the decision tree model is set as a comparative test model.The results show that compared with the decision tree model,the GWO-SVR model has higher prediction accuracy.Finally,a new set of experimental data is introduced for model validation,and finally it is proved that the GWO-SVR model is still suitable for the prediction of the interface bonding strength between a new set of FRP reinforcements and concrete.