Mechanical Behavior And Design Method For Large Capacity Iron Tailings High-strength Concrete Beams

In order to reduce iron tailing stacking for environmental pollution,turning waste into treasure,which is used as a component for the preparation of large volume iron tailings high-strength concrete.It is composed of iron tailings,iron tailings power,cement,silica fume,fly ash,and superplasticizer.The composition of the concrete with no coarse aggregate is different from that of the ordinary concrete,and the basic mechanical properties of the two kinds of concrete are also different.The mechanical properties and calculation of the iron tailings high-strength concrete member are also different from those of ordinary concrete.Therefore,it is necessary to study the ratio and basic mechanical properties of iron tailings high-strength concrete,and to explore the mechanical properties and calculation theory of iron tailings high-strength concrete members.Based on the above ideas,this paper has carried on the research work to the following aspects:At first,to explore the different water-cement ratio,fly ash instead of cement and silica fume and the type of superplasticizer on the strength and fluidity of iron tailings high-strength concrete.Conducted a 13 group match tests,through the test,the greatest impact on the strength of concrete is the water-cement ratio.Polycarboxylate water reducing agent and naphthalene superplasticizer compared to the effect of water reduction,the former better.Compared of reference mix concrete,the concrete strength of using fly ash to replace cement 10%,instead of silica fume 18%declined,iron tailings high-strength concrete costs from 589 yuan/square down to 515yuan/square,the economic benefits are obvious,and the concrete strength can still reach 65~70MPa,The best mix ratio of iron tailings high-strength concrete used in the test.Second,six axial compression test specimens with dimensions of100mm×100mm×300mm and six axial tensile specimens with dimensions of100mm×100mm×400mm were prepared.The axial compression test and tensile test of the iron tailings high-strength concrete prism were carried out.The results show that the average value of compressive strength of iron tailings high-strength concrete is 53.23MPa,the average value of axial tensile strength is 1.61MPa,the average value of elastic modulus is 2.36×10~4MPa,and the average value of the Poisson's ratio is0.23.The relationship between axial and compressive stress-strain equations is obtained.Third,the influence of different reinforcement ratio on the bearing capacity of beams and the influence of different reinforcement diameters on the development of flexural crack of beams under the same reinforcement ratio are studied.Through the test results,the greater the reinforcement ratio of the tensioned steel bar,the greater the bearing capacity of the beam cross section,the same of the reinforcement ratio and the steel strength grade,the preparation of the smaller diameter of the reinforced concrete and the number of cracks is reduced.Through the bending test of the tailrace concrete beam,the failure phenomenon is obtained,which provides the experimental basis for the engineering application.At last,the structure of the iron tailings high-strength concrete-ordinary concrete composite beams is put forward.The low strength ordinary concrete and high strength grade steel were cast the lower,the iron tailings high-strength concrete was cast the upper.The calculation formula of neutral axis of composite beams was derived.Four iron tailings high-strength concrete and normal concrete composite beams were fabricated and bending performance with third point loading was tested.The results point out that the bonding performance of two different concrete interfaces is good,and various materials are full used.Equivalent rectangular stress diagram pattern factor and calculation of flexural formula are fitted,and relative compression zone height limit and reinforcement ratio limit are also proposed.