Research On Application Of Steel Fiber And Polymer In Defects Repair Of Concrete Bridge Structures

Today,more and more defects happened in concrete bridges,this became more and more serious,and would require for repairing materials and repairing technology more strictly.This thesis mainly explores the application of polymer and steel fiber in the repair of concrete bridge structure defects,and obtains the results that have practical application value.The main research contents can be summarized as following:①Polymer cement paste was used to deal with micro-cracks,short-cut steel fiber polymer cement mortar was used to deal with wide cracks,and short-cut steel fiber reinforced polymer concrete was used to deal with severe denudation on the concrete surface.According to the characteristics of the repaired structure,the technical performance indicators of the above three types of repair materials are proposed,and the composition and mix ratio design of the materials are given.Through the basic anti-pressure and flexural tests,the influence of the different content of steel fiber and polymer on the mechanical properties of concrete was investigated.Through orthogonal test,it found that the incorporation of steel fibers in concrete can greatly increase the compressive and flexural strength of concrete;incorporation of polymers in concrete would reduce the compressive and flexural strength of concrete.②Through core drilling and interface shear tests,the effects of interface treatment methods,maximum particle size of coarse aggregates,types of repair materials,curing conditions,molding process,and slight vibrations on the interface properties of new and old concrete were explored.The test results showed that the interfacial agent and the interface roughness can improve the interfacial adhesion performance at the interface of the new and old concrete,and the combination of the two had better effect.The proper reduction of the maximum particle size of the coarse aggregate can enhance the interfacial adhesion performance;The humidity of the environment can enhance the interfacial adhesion properties of the new and old concrete to a certain extent;under the influence of the gravity of the newly cast concrete itself,the side bonding was not as good as the above surface bonding effect.③Through the three-point bending fracture test,the influence of factors such as the incorporation of steel fibers and polymers,the maximum particle size of repaired material coarse aggregates,the thickness of different repair layers,and slight vibration on the fracture properties of new and old concrete was investigated.The test results showed that the compounding of 0.6%steel fiber and 6%polymer in the repair material can greatly enhance the toughness and overall strength of the new and old concrete composites,and achieve the effect of strengthening and toughening;The implantation had greatly improved the fracture performance of new and old concrete;minor vibration occurred during the different setting times of new concrete,and had different degrees of impact on the fracture properties of the new and old concrete composites.④ Three different width cracks were simulated and three repair material materials were designed:polymer modified cement paste,chopped steel fiber polymer cement mortar and chopped steel fiber polymer fine-grained concrete.Three kinds of cracks with different widths were repaired,and then a sulfate resistance erosion test was conducted.The results were compared with the conventional ordinary repair materials,and good results were obtained.