Study On Properties Of Fiber Modified Mechanism Sand Concrete With High Stone Powder Content

With the increasing scale of infrastructure construction in China,the demand for building materials is increasing.The main source of concrete fine aggregate is the excessive exploitation of natural sand,which leads to resource depletion and environmental damage.The use of machine-made sand instead of natural sand as concrete aggregate is one of the ways to solve this problem.The content of stone powder in machine-made sand is a difficult problem in practical engineering.Stone powder is a by-product in the production of manufactured sand.Proper amount of stone powder can improve the gradation of concrete and play a positive role in the performance of concrete.The high content of stone powder will result in the decrease of concrete strength and the increase of strength dispersion.At the same time,the waste stone powder will cause serious pollution to the environment and water resources,and the cost of comprehensive treatment will be high and difficult.Based on the high content of machine-made sand powder in practical engineering,this paper considers the incorporation of fiber into the machine-made sand concrete with high stone content to improve the mechanical properties of concrete.1.Through experiments,the mechanical properties of mortar with different content of fiber reinforced with high stone content were modified.The 10%,15%and20%kinds of machine-made sand mortars with quality content were designed,and 4kinds of fiber mixing ratios of CSW,1 kg/m~3and 1.5 kg/m~3 of 5 kg/m~3 and 10 kg/m~3were prepared by using calcium sulfate whisker(CSW)and polypropylene fiber(PPF)two fibers.A total of 15 sets of specimens were tested.The cube compressive strength and flexural strength of the mortar under different stone powder content and fiber content were tested.The test results showed that the mechanical properties of high stone powder manufactured sand mortar were obviously improved by adding CSW.The mortar mixed with CSW had higher compressive strength and flexural strength than the common mortar,and the modification effect was better.When CSW content is5 kg/m~3,the modification effect is the best.PPF has a low modification effect on the compressive strength of mortar,but the influence of flexural strength is obvious.The best dosage of PPF is 1 kg/m~3.2.By modifying the compressive strength and modulus of elasticity of high stone powder machine-made sand concrete by adding different CSW and PPF,the optimum content of CSW and PPF is determined through mortar mechanical property test.2kinds of fiber(5 kg/m~3CSW,1 kg/m~3 PPF)and 3 kinds of stone powder content(10%,15%and 20%)were designed,and the cube compressive strength,prism compressive strength and elastic modulus of the machine-made sand concrete specimens of 27groups were tested.The results showed that the mixing of CSW and PPF changed the best dosage of stone powder:after mixing CSW,the best addition of stone powder was 15%,and the best dosage of stone powder was 15%after adding PPF.At the same time,because of the high strength and elastic modulus of CSW,the modification of concrete after concrete incorporation is more obvious than that of PPF.3.Considering the influence of the addition of stone powder on aggregate density,based on the concrete compressible packing model,the strength model of machine-made sand concrete considering the content of stone powder is established.Based on the theory of composite materials,the modification effect of fiber on concrete is considered in two aspects,namely,the influence of fiber on cement paste,and the enhancement of fiber on the spatial structure of concrete.The strength model of fiber modified high stone powder machine-made sand concrete is established,and the parameters of the model are determined based on the test data.4.Based on the three fold ball model of concrete elastic modulus and the theory of composite materials,the influence of rock powder adhesion on the aggregate surface is considered,and the interface transition zone of concrete is affected.The influence coefficient of interfacial transition zone on the elastic modulus of concrete is defined,and the functional relationship between the coefficient and stone powder content is analyzed by regression analysis of experimental data.Considering the modification effect of fiber on the spatial structure of cement paste and aggregate,the elastic modulus model of fiber modified high stone powder machine-made sand concrete is established.5.The fiber reinforced high stone content machine-made sand concrete is applied to the actual engineering structure.The finite element model of the underground concrete station of a city in Western China is established by using Plaxis 3D.The deformation difference of the station structure with different fiber modified high stone powder machine-made sand concrete is studied.The deformation of the subway station structure with common machine-made sand concrete is taken as the benchmark.The geometric size of the components that can be reduced by using fiber reinforced concrete to make local components of the station is calculated.The economic and environmental benefits of fiber modified sand concrete are analyzed from the material point by using the construction quota list of open cut station and the LCA database of CLCD localization.