Study On Properties Of Hybrid Fiber Non-coarse Aggregate Concrete

The development of concrete went through three stages: traditional concrete,high-strength concrete and high-performance concrete.In high-performance concrete,there are several representative non-coarse aggregate concrete,namely reactive powder concrete(RPC),Macro-Defect-Free cement-based composite(MDF),ultra high toughness cement-based composite(ECC)and Geopolymer concrete,which are used to solve the problems of poor working performance,low strength,high compression-fold ratio,low toughness and poor durability of concrete,as well as the problems of ecological environment protection and resource recycling.Hybrid fiber non-coarse aggregate concrete draws lessons from the design ideas of mixing ratio of reactive powder concrete(RPC)and ultra high toughness cement-based composite(ECC).In hybrid fiber non-coarse aggregate concrete,coarse aggregate is removed from concrete,mineral admixtures and hybrid fibers are added to improve or enhance the working performance,the strength of concrete,toughness and durability by making full use of the powder reinforcement effect of mineral admixtures and the hybrid effect of hybrid fibers.Basing on the fluidity test,the compressive strength test,the flexural strength test and the shrinkage test.1)Exploring the effect of mineral admixtures(silica fume,fly ash,micro-beads and mineral powder)on the working performance,mechanical strength and shrinkage performance of cement mortar by orthogonal test method with four factors and three levels,and then determining the reference mix ratio of non-coarse aggregate concrete.2)Based on the reference mix ratio of non-coarse aggregate concrete,exploring the influence of fiber volume fraction on the fluidity,strength and toughness of single fiber non-coarse aggregate concrete when steel fiber or polypropylene fiber is added alone by using single factor variable analysis method;studying the influence of fiber volume fraction on the fluidity,strength and toughness of hybrid fiber non-coarse aggregate concrete when steel fiber and polypropylene fiber are mixed simultaneously.The main results are as follows:1)According to the results of range analysis,obtaining the significant level of the influence of mineral admixtures on the working performance,mechanical strength and shrinkage of cement mortar.2)Obtaining the influence result of mineral admixtures(silica fume,fly ash,micro-beads and mineral powder)on the working performance,mechanical strength and shrinkage of cement mortar,and determining the reference mix ratio of non-coarse aggregate concrete.Cement: mineral powder: micro-beads: silica fume: sand =1000:50:100:900.3)Obtaining the development trend of working performance,strength and toughness of single fiber non-coarse aggregate concrete and the development trend of working performance,strength and toughness of hybrid fiber non-coarse aggregate concrete with the change of volume fraction of fiber.4)Obtained the load-deflection curves of steel fiber non-coarse aggregate concrete,polypropylene fiber non-coarse aggregate concrete and steel-polypropylene hybrid fiber non-coarse aggregate concrete.5)Preparing a hybrid fiber non-coarse aggregate concrete with 1.5% steel fiber and0.5% polypropylene fiber.Its fluidity is 160 mm,compressive strength is 114.4 MPa,flexural strength is 19.2 MPa,toughness index is 5.62,and equivalent flexural strength is 8.38 MPa.The concrete has the characteristics of self-compacting,high strength and high toughness.