Research On Performance Of Hybrid Fiber High-strength Self-compacting Concrete

Since its birth,concrete is still the main building material we use,and people’s research on concrete is also constantly improving.At present,in order to cope with various construction needs,people have developed many new types of concrete,such as: asphalt concrete,fiber concrete,high-strength concrete,self-compacting concrete,etc.Compared with other concretes,the biggest feature of self-compacting concrete is that it can be formed without vibrating,which avoids problems such as the difficulty of vibrating and compacting at some nodes and the reduction of structural quality,which makes self-compacting concrete attract widespread attention.In the case of the same water-binder ratio,the strength of self-compacting concrete is much lower than that of ordinary concrete,and at the same strength,the water-binder ratio of self-compacting concrete is much lower than that of ordinary concrete.The water-binder ratio of high-strength self-compacting concrete will be very low when the strength is increased.At the same time,under the action of its own shrinkage and environmental factors,the toughness will be reduced,and it will be easy to crack.The durability is reduced.In order to solve this problem,related studies have shown that fiber modification can effectively enhance the toughness of concrete.In this paper,carbon nanotubes and steel fibers with excellent mechanical properties and electrical conductivity are mixed to prepare hybrid fiber high-strength self-compacting concrete.Work performance and mechanical properties,the main work is as follows:(1)Describe the current research status of self-compacting concrete,and analyze the feasibility of fiber for improving the crack resistance and toughness effect of high-strength self-compacting concrete.The reference mix ratio of the self-compacting concrete is obtained through the ratio calculation,and the prediction ability of the BP neural network is used to reduce the workload of the trial mix during the trial mix process,combined with the work performance test such as the slump expansion and the J-ring expansion,obtain The best benchmark mix ratio.(2)Study the working performance of self-compacting concrete with different fiber content,and explore the influence of steel fiber and carbon nanotube on the working performance of high-strength self-compacting concrete.Through the experiment,it is concluded that the flow performance of high-strength self-compacting concrete decreases with the increase of the amount of steel fiber;when the carbon nanotube fiber is added alone,the flow performance of the concrete increases with the increase of the carbon nanotube fiber.The improvement in working performance is most obvious when the two types of fibers are blended;when the two types of fibers are blended,the flow performance increases with the content of carbon nanotube fibers,reaching the highest when the content of carbon nanotubes reaches 0.2%,and then with carbon nanotubes.When the fiber content increases,the flow performance of concrete decreases.(3)Investigate the influence of steel fiber and carbon nanotube fiber on the mechanical properties of high-strength self-compacting concrete in the case of single admixture and mixing,and find the best fiber content.Through experiments,it is concluded that when the content of steel fiber is 1.8% and the content of P-CNT is 0.2%,the working performance is satisfied and the mechanical performance is the best.(4)Further analyze the effect of steel fibers and carbon nanotube fibers on the early cracking of high-strength self-compacting concrete through the flat-plate crack resistance test.To study the effect of carbon nanotube fibers on the bending toughness of steel fiber high-strength self-compacting concrete under the optimal steel fiber content,and calculate the bending toughness ratio through the load-displacement curve to measure the toughness of carbon nanotubes for high-strength self-compacting concrete The promotion situation.According to the test,under the premise of satisfying the working performance,the steel fiber content is 1.2% and 1.8%,and the P-CNT content is 0.2%,and the crack resistance is close,and both have reached the first-level crack limiting performance level;When the fiber content is 1.8%,different P-CNT content has a certain effect on the flexural toughness of hybrid fiber self-compacting concrete,which is mainly reflected in the crack propagation stage.When the P-CNT content is 0.3%,the bending toughness of the specimen is the best.Good,the best ductility.(5)Investigate whether the test piece contains water and the influence of size effect on the electrical polarization of the test piece,conduct polarization tests on two sizes of40×40×160mm and 150×150×150mm,and select the appropriate size test piece to carry out the cyclic loading system Under the pressure sensitivity test,study the pressure sensitivity of the test piece.