Study On Physical And Mechanical Properties Of Steel Fiber High Strength Self-compacting Concrete

As a new type of green high-performance concrete,self-compacting concrete(SCC)is widely used in complex components or key projects because of its good workability,no noise and easy construction.With the increasing requirements for the bearing capacity of concrete members in tunnel engineering,marine engineering structures,long-span and super high-rise buildings,the preparation technology and Performance Research of high-strength SCC have attracted extensive attention.In order to alleviate the problems of high brittleness and high hydration heat brought by high-strength concrete,this topic uses silica fume and fly ash mineral admixture to improve the flow performance and mechanical properties of SCC,improves the deformation performance and bearing capacity of SCC under different load conditions through the toughening and crack resistance of steel fiber,and prepares C80 SCC with excellent mechanical properties.On the basis of fixed cementitious material content and fly ash content of 20%,high-strength SCC and steel fiber high-strength SCC are prepared by adjusting the mix proportion parameters such as silica fume,steel fiber,sand ratio and water reducer.Through the compressive strength,flexural strength,splitting tensile strength,four-point bending test and three-point bending beam test with notch,the effects of silica fume content(0%,2%,4%,6%,8%)and steel fiber content(0%,0.3%,0.6%,0.9%,1.2%)on the mechanical properties,shrinkage properties,bending deformation properties and fracture mechanical properties of high-strength SCC and steel fiber high-strength SCC are studied,and their action mechanism is further analyzed.The following conclusions are obtained:(1)Workability and mechanical properties of high strength SCC and steel fiber high strength SCC.The slump expansion degree and j-ring expansion degree of high-strength SCC decrease with the increase of silica fume content.Increasing the sand rate can improve the workability of the mixture;Steel fiber can significantly degrade the workability of the mixture and slightly improve the compressive strength of high-strength SCC;With the increase of steel fiber volume fraction,the splitting tensile strength and flexural strength of the specimen increase gradually;The compressive strength of high-strength SCC increases first and then decreases with the increase of silica fume content.When the silica fume content is 4%,the28 d strength reaches 94.2MPa,and the variation laws of splitting tensile strength,flexural strength and elastic modulus are basically consistent with the compressive strength.(2)Bending deformation properties of high-strength SCC and steel fiber high-strength SCC.The peak load,peak deflection and flexural toughness of high-strength SCC increased first and then decreased with the increase of silica fume content,and the flexural deformation property increased slightly;When the content of silica fume increased to 8%,the peak load of the specimen decreased by 12.4% compared with the reference group;After adding steel fiber,the bending deformation performance of high-strength SCC is significantly improved,and its peak load,peak deflection and bending toughness ratio continue to increase with the increase of steel fiber content.When the steel fiber content is 1.2v%,the bending toughness ratio of the specimen reaches the maximum value of 0.72,which is 6 times higher than that of the reference group.(3)Fracture mechanical properties of high strength SCC and steel fiber high strength SCC.The fracture toughness and fracture energy of high-strength SCC increased first and then decreased with the increase of silica fume volume content,and increased the most when the silica fume content was 4%.When the silica fume content increased to 8%,the fracture toughness of the specimen was lower than that of the reference group;The addition of steel fiber can effectively improve the fracture toughness and fracture energy of the specimen.With the increase of the volume fraction of steel fiber,the fracture energy of the specimen continues to increase,and the maximum fracture energy reaches 7015.4N/m when the volume fraction of steel fiber is 1.2%,which is 35.6 times higher than that of the reference group.