Study On The Application Of Slag Me Chanism Sand In C50 Cement Concrete

In order to solve the problem of insufficient supply and demand of natural sand and high cost in the construction of expressway in mountainous areas,the sand production mechanism of tunnel excavation and slag abandonment is adopted as the fine aggregate of concrete,which plays a role in the sustainable development of China’s infrastructure and environmental protection,and realizes the reuse of resources.For this reason,a large number of experiments and studies have been conducted on the application of mechanism sand produced by tunnel slag dumping to C50 concrete.The main work and conclusions are as follows:First,the characteristics of the crushing process of tunnel slag abandonment,the advantages and disadvantages of different types of sand making machines and the dust removal process are compared and analyzed.Determined to take "jaw crusher +counterattack crusher" as wool crushing combination,using Adobe Lightrom image analysis software for different types of sand making machine of particles of mechanism sand production by characteristic parameters were calculated,and establish a particle flow characteristic parameters and time correlation,finalized the vertical shaft type sand machine production mechanism sand dry legal system.The results show that the fineness modulus of the mechanism sand is stable between 2.5～3.3,and the content of the stone powder is 9.3% at most and 2.8% at least.At the same time,the crushing value and MB value of the sample meet the requirements of the specification.Second,With dosage of cement,water cement ratio,sand ratio,dosage of water reducing agent as a major factor in design of four factors three levels orthogonal test table and use the poor analysis,variance analysis and data processing methods of optimization of parameter,and performance verification experiment was carried out,in combination with the practical situation of engineering and engineering experience to determine the parameters for the cement dosage of 455 kg/m3,water/cement ratio is 0.30,sand rate was40%,the dosage of water reducing agent is 1.0%.Third,The effects of the content,gradation,sand shape characteristics and MB value on the workability,mechanical property,shrinkage property and durability of the mechanical sand concrete were studied.The experimental results show that: with the increase of stone powder content,the slump of the concrete increases first,and then decreases gradually when the content exceeds 5.4%.Meanwhile,the cohesion and water retention of the concrete mixture also improve.When the content of mechanical sand and gravel powder is 5.4%,the maximum compressive strength of concrete under 28 d standard is 73.1mpa,while the splitting tensile strength increases with the increase of stone powder content.The shrinkage performance of mechanism sand concrete increases with the increase of stone powder content.When the stone powder content exceeds 5.4%,the dry shrinkage strain value decreases.The chloride penetration resistance of the mechanical sand concrete decreased with the increase of stone powder content,and decreased with the extension of health age,while the frost resistance and sulfate resistance showed better performance when the stone powder content was 5.4%.The performance of concrete can be improved by the proper proportion of graded grain size,the adoption of proper production mechanism sand machine and the good control measures of silt powder.Fourth,based on the cast-in-place box girder of solid project,the key points of construction technology and quality control are summarized,and the feasibility of the application of mechanism sand produced by tunnel slag abandonment in C50 concrete can be considered through spot sampling inspection of slump and post-forming strength of mechanism sand concrete.