Preparation Of Light Aggregate From Solid Waste And Its Treatment Influence Of Concrete Performance And Beam Bending Performance

On the one hand,the rapid advancement of urbanization has caused a huge increase in the demand for construction materials such as sand and gravel,which poses great challenges to resource conservation and environmental protection.On the other hand,the persistent solid waste emissions have also caused environmental pollution.Urgently.Studies have shown that most solid wastes have the same composition as building materials,so it is of great significance to use solid wastes to prepare aggregates for replacing natural gravel aggregates in concrete.In this paper,based on the use of fly ash to prepare light aggregate,fine yellow sand is used as aggregate,and mechanically activated waste concrete powder is used as active cementitious material to improve the performance of aggregate and The physical and mechanical properties of the prepared lightweight aggregate were studied.With reference to the current relevant specifications,the mix ratio of lightweight aggregate concrete is designed,and the influence of aggregate properties on the physical and mechanical properties of concrete is analyzed.Select the lightest aggregate with the best performance,replace its crushed aggregate with equal volume,design four groups of concrete,and test its working performance and physical and mechanical properties.Finally,a normal section flexural performance experiment was designed to test and analyze the flexural performance of the component.The main research contents and results are as follows:Using fly ash as siliceous material and cement as calcium material,based on autoclave to prepare light aggregate,fine yellow sand is used as aggregate,waste concrete powder is used as a material with gelling effect to improve light bone Material properties.Analyze and test its apparent density,water absorption rate and cylinder pressure strength.The results show that:after mixing fine yellow sand as aggregate,the prepared light aggregate is more dense,and the cylinder pressure strength of the light aggregate is increased by 24.6%～63.5%,the water absorption is reduced by 23.1%～72.3%,the performance of light aggregate is the best when the amount of fine yellow sand is 5%;the active powder in which the waste concrete powder is mixed acts as a cementing material,so that The barrel compression strength of light aggregate is increased by 29.3%～62.7%,and the water absorption rate increases first and then decreases with the increase of the mixing amount.When the mixing amount of waste concrete powder is 30%,the performance of light aggregate optimal.Select the improved high-performance light aggregate,design the general crushed concrete(NC),mixed aggregate concrete with light aggregate volume replacement rate of50%(RC50),light aggregate with volume substitution rate of 100%Concrete(RC100),light aggregate with 100%volume substitution rate and 40%volume substitution rate with cloud concrete sand(QRC).the four groups of concrete were used to test the performance.The results show that the slump fluidity of the concrete mixture increases with the increase of the volume substitution rate of the light aggregate,and the slump of the QRC reaches the maximum value of 255 mm;the compressive strength of the concrete mixes with the light aggregate The volume substitution rate increases gradually,the minimum value is 55.3 MPa,the maximum value is 65.4 MPa,and the maximum can be increased by 18.2%;the elastic modulus and apparent density decrease with the increase of the volume replacement rate of light aggregate,and the elastic modulus The minimum value is 28.3GPa,the maximum value is 36.1GPa,a decrease of 21.6%;the maximum value of the apparent density is 2283kg/m~3,and the minimum value is 1916kg/m~3,a decrease of 16.1%.Based on the mix ratio of the four groups of concrete,four groups of concrete test beams were designed to study their flexural performance.The structure shows that as the volume replacement rate of light aggregate increases,the normal section bearing capacity,deflection,maximum crack width and crack number of the concrete experimental beam increase accordingly.According to the current specifications,the bearing capacity,deflection,maximum crack width and crack spacing are calculated.The results show that the ratios of the calculation results of the four groups of test beams(NC,RC50,RC100,QRC)to the experimental results are:1.146,1.203,1.275,1.365;the ratio of the calculated results of deflection and the experimental results are:1.098,1.164,1.200,1.267;the ratio of the calculated results of the maximum crack width and the experimental results are:0.907,0.913,0.976,0.990,respectively.It shows that the calculation formulas for the bearing capacity,deflection,and maximum crack width of the normal section in the current specification can also be applied to the concrete with the same volume of aggregate instead of crushed stone in this article.The definition of deflection and maximum crack width in the code,in the concrete experimental beam,with the increase of the volume replacement rate of light aggregate,its deflection value always meets the requirements of the specification;and with the increase of the volume replacement rate of light aggregate,The maximum crack width of the experimental beam exceeded the maximum limit of the specification.