Preparation And Microstructure Study Of Iron Tailing Based Cementitious Composite Materials Reinforced By ATP-BF

Iron tailing is a kind of solid waste generated by the iron and steel industry,which is in urgent need of resource utilization.Iron tailing can be used as aggregates to prepare cementitious composite materials.When iron tailing was applied to building materials,fibers need to be added to enhance mechanical performance.Basalt fiber is a good choice for reinforcing fiber.However,the surface of basalt fiber is smooth,so it is difficult to bond with the matrix material to form an interface,and the enhancement effect is limited.Therefore,this thesis uses the special fibrous structure of attapulgite to modify basalt fiber,and prepares attapulgite modified basalt fiber with greatly improved surface roughness to enhance iron tailing based cementitious composite material.Through comparative experiments of various modification methods,the surface modification effect of attapulgite on basalt fibers was explored.Characterization methods such as SEM,FTIR,and XPS confirmed that attapulgite was grafted on the surface of basalt fiber by chemical bond,and the attapulgite modified basalt fiber prepared by the method of Na OH etching and KH-550 coupling agent synergistic modification method had the best modification effect.The surface roughness of basalt fiber is significantly improved.By exploring the different ratio of aggregates and silicocalcium mineral admixtures,an optimized ratio of iron tailing based cementitious composite materials was designed.When attapulgite modified basalt fiber was added,the 3-day flexural strength of the iron tailing based cementitious composite material reaches 9.32 MPa,which is 62.4% higher than that of the test block without fiber,and 15.6% higher than that of the test block with the unmodified basalt fiber.Through XRD,FTIR and other technical means,it is analyzed that the toughness enhancement mechanism of attapulgite modified basalt fiber to the iron tailing based cementitious composite material was analyzed.The results show that after the modification of attapulgite,the dispersion of basalt fibers in the matrix material was improved,forming a cross-linked interface with the hydration product C-S-H gel;the average pore size of the matrix material was reduced,and the distribution of small size pores is uniform,forming a more dense structure;the silicate minerals in the hydration products of the matrix material have an increased tendency to develop into layered silicate.Through the 3D printing experiment,it is analyzed that attapulgite modified basalt fiber still significantly improved the mechanical properties of 3D printed iron tailing based cementitious composite material.The 28-day flexural strength reaches 14.94 MPa,which is 55.8% higher than that of the test block without fiber,and 17.8% higher than that of the test block with unmodified basalt fiber.The 3D printed attapulgite modified basalt fiber reinforced iron tailing based cementitious composite material after 28 days of hydration could reach 32.86 MPa,which reaches the C30 concrete standard.This thesis makes an innovative research on the modification of basalt fiber,and proposes effective solutions for enhancement of iron tailing based cementitious composite material.