Research On Mechanical Properties And Engineering Applications Of Mixed Fiber Iron Tailings RPC

Reactive Powder Concrete(RPC)consists of cement,silica fume,quartz sand,quartz powder,etc.It has good strength and durability,but the expensive price of quartz powder leads to the high cost of RPC.Therefore,reducing the economic cost is an important issue facing RPC.In this thesis,the quartz powder in RPC is replaced by industrial waste iron tailing powder,and steel fiber and polypropylene fiber are also blended to prepare mixed-fiber iron tailing RPC,and the basic mechanical properties of mixed-fiber iron tailing RPC are studied and the optimal fitting ratio is obtained by orthogonal test method.On this basis,axial compressive tests were conducted to analyze its deformation capacity,and the stress-strain curve equation was fitted and the characteristic parameters of the curve were discussed.The mixed fiber iron tailing RPC with high strength and high toughness was obtained through the above tests,and in order to investigate its engineering application value,a rail pillow model was established using finite element software for related analysis,and the results proved that the mixed fiber iron tailing RPC can be applied to railroad rail pillow engineering.The main research contents are as follows:(1)The physical and mechanical properties of iron tailing RPC were tested,and all the quartz powder in RPC was replaced with iron tailing powder to obtain iron tailing RPC.the properties of iron tailing RPC and common RPC were compared from the physical and mechanical points of view respectively,and it was finally determined that iron tailing RPC has good flow and mechanical properties,and the test base mix ratio was obtained.(2)Based on the four-factor four-level orthogonal test method,the effects of different watercement ratio,steel fiber doping,polypropylene fiber doping and polypropylene fiber length on the flow,compressive strength,splitting tensile strength and flexural strength of blended fiber iron tailings RPC were investigated,and the damage patterns of blended fiber iron tailings RPC mechanical properties tests were analyzed.The test data were analyzed by extreme difference analysis,analysis of variance and regression fitting,and the optimal test mix ratio was determined:water-cement ratio 0.2,steel fiber dosing 1.8%,polypropylene fiber dosing 0.2%,and polypropylene fiber length 15 mm.(3)On the basis of the test optimal fit ratio,axial compressive tests were conducted to further investigate the deformation capacity of mixed fiber iron tailings RPC.At the same time,the stress-strain curve of mixed fiber iron tailings RPC was fitted and derived,and the equation of axial compressive stress-strain curve with good fitting effect was obtained,and the main characteristic values of the curve: axial compressive strength,peak strain,proportional limit,elastic modulus and Poisson’s ratio were analyzed.The results show that steel fibers have a greater effect on the axial compressive strength,while polypropylene fibers can significantly increase the peak strain of mixed-fiber iron tailings RPC.(4)Based on the finite element simulation,the damage,displacement,stress,bending moment and impact bearing capacity of the two types of rail sleepers were analyzed under static and transient loads using ABAQUS software and LS-DYNA software by establishing mixed fiber iron tailings RPC rail sleeper and concrete rail sleeper models,respectively.The results show that the damage,displacement and stress conditions of mixed fiber iron tailings RPC are better than those of concrete rail sleepers and can be applied to railroad rail sleepers.