Experimental Study On Thermal Insulation Shotcrete With Ceramsite,Vitrified Beads And Straw Fibers

The high temperature environment of deep mine roadway is easy to cause heat stroke,metabolic disorder and other physiological function damage to the operating workers.At the same time,it will also accelerate the aging of underground materials and equipments,which not only affects the economic benefits of coal mining,but also brings hidden hazards to the safety production of underground mines.In order to reduce the adverse effect of high temperature in deep mine roadway on work environment and improve the economic benefit of coal mining,based on the heat transfer principle of deep mine roadway,this paper designs the ceramsite-vitrified beads-straw fibers thermal insulation shotcrete by mixing a certain proportion of the low thermal conductivity and low cost thermal insulation materials(ceramsite,vitrified beads and straw fibers)to ordinary concrete.The compressive strength,tensile strength,thermal conductivity and the thermal conductivity after carbonization of thermal insulation shotcrete were measured by the orthogonal experimental design.The specific research contents are as follows:Firstly,the mix ratio of shotcrete is designed preliminarily,and the final mix ratio is determined by the modification of mix ratio through preliminary experiments.The final mix ratio is:cement:stone:sand:water=1:2.15:0.88:0.55.The compressive strength and slump of plain concrete with this mix ratio are measured previously.The final compressive strength is 31.6 MPa for 28 days and slump is 110 mm,which meets the strength and workability requirements of C25 sprayed concrete.Secondly,based on the final mix ratio,a certain proportion of fly ash,ceramsite,vitrified beads and straw fibers was added to form ceramsite-vitrified beads-straw fibers thermal insulation shotcrete(the fly ash content is calculated according to 10%of the cement quality,the content of ceramsite is calculated according to 0%,5%,10%and 15%of the mass of stones,the mixing amount of vitrified beads is calculated as 0%,10%,20%and 30%of the unit volume of concrete,the content of straw fibers is calculated by 0%,2%and 4%of the unit volume of concrete).The compressive strength of thermal insulation shotcrete was tested,and the compressive strength of 7d,14d and 28d was obtained.It is found that the addition of ceramsite,vitrified beads and straw fibers will reduce the compressive strength of thermal insulation shotcrete.By combining range analysis,grey relational degree analysis and layered analysis method,the primary and secondary order of the influence of ceramsite,vitrified beads and straw fibers on the early and final compressive strength of thermal insulation shotcrete and the proportion of the influence on the final compressive strength were obtained.Thirdly,the tensile strengths of thermal insulation shotcrete of 7d,14d and 28d were obtained by the tensile strength test.It was found that the compressive strength of concrete will be reduced by adding ceramsite and vitrified beads,and the tensile strength of concrete will be improved by adding straw fibers.Using the range analysis,grey relational degree analysis and layered analysis method,the primary and secondary order of the influence of ceramsite,vitrified beads and straw fibers on the early and final tensile strength of thermal insulation shotcrete was obtained,as well as the proportion of the influence on the final tensile strength.Fourthly,the thermal conductivities of thermal insulation shotcrete of 7,14 and 28 days of curing age were obtained by the thermal conductivity test.It was found that the thermal conductivity of concrete will be reduced and the thermal insulation performance of concrete will be improved by adding ceramsite,vitrified beads and straw fibers.Combining grey relational degree analysis and layered analysis,the influence order and proportion of ceramsite,vitrified beads and straw fibers on thermal insulation performance of thermal insulation shotcrete were obtained.Finally,the thermal insulation shotcrete of 28 days curing age was treated by carbonization for a period of 14 days,and the thermal conductivity of thermal insulation shotcrete after carbonization was measured.It was found that the thermal conductivity of concrete after carbonization was higher than that of the concrete before carbonization,but it was lower than that of the plain concrete at the same curing age.Ceramsite,vitrified beads and straw fibers could improve the carbonization resistance of concrete to a certain extent,thereby reducing the decline of thermal insulation performance of concrete.The grey relational degree analysis of the increment of thermal conductivity was performed,and the primary and secondary order of the influence of ceramsite,vitrified beads and straw fibers on the carbonation resistance of concrete was obtained.Figure 44 table 45 references 58...