Properties Of The Foamed Lightweight Soil Containing Gold Tailings And Mineral Powder And Carbide Slag And Cement Cementitious Material

Foamed lightweight soil has many characteristics such as light weight,high strength,good self-reliance and easy adjustment.It is widely used in bridgehead jump treatment,highway reconstruction and expansion,new construction,soft soil roadbed section treatment,special area construction and so on.However,the large amount of cement in ordinary foamed lightweight soil not only costs a lot,but also wastes a lot of resources and leads to serious atmospheric and environmental pollution.In response to this problem,this paper uses carbide slag-tailings-mineral powder-cement quaternary cementitious system to prepare foamed lightweight soil.Not only does it make efficient use of solid waste,but it also reduce cement consumption and carbon emissions,which is in line with the concept of green development.In this paper,the mechanical properties of multi-component solid waste cementitious materials were studied,and the working performance,mechanical properties,durability and micro-pore structure of tailings-slag-carbide slag foamed lightweight soil were further studied.The main conclusions are as follows:(1)Based on tailings,mineral powder and carbide slag,a multi-component solid wastebased cementitious material was developed to work synergistically with cement.Through the compressive and flexural strength test of mortar specimens,the optimum mass ratio of cement to mineral powder and the optimum content of carbide slag were detennined.The results show that when the ratio of cement and slag is 1:1,the content of carbide slag increases,the mechanical strength of mortar increases,and the early hydration rate and cumulative hydration heat of solid waste cementitious materials also increase.It is confirmed that the alkaline environment provided by carbide slag effectively stimulates the activity of slag.(2)Foamed lightweight soil was prepared by using solid waste cementitious materials.The influence of tailings on mechanical indexes of light soil under different wet densities,including static elastic modulus,compressive and splitting strength,CBR,was studied by mechanical tests.It is found that tailings content is negatively correlated with the above indexes,and the wet density is positively correlated with the above indexes.In order to meet the requirements of subgrade filling,the minimum cement content of lightweight soil with 600kg/m3 wet density is 30%,and its 28d compressive strength value is 1.05MPa.The minimum cement content of 700kg/m3 wet density is 25%,and the 28d compressive strength value is 0.83MPa.Using the fitted relational expression between compressive strength and tailings content,it is predicted that the minimum cement content of lightweight soil with 800kg/m3 wet density is 17%.(3)Through durability test,including:long-term immersion,wet and dry cycle,freezethaw test,etc,the results show that tailings can reduce the early drying shrinkage of foamed lightweight soil.Under the 40%tailings content,the compressive strength of the three kinds of wet density lightweight soil is still greater than 0.8MPa after 30 dry-wet cycles,which meets the requirements of the specification.The tailings-slag-carbide slag foamed lightweight soil has good frost resistance.After 30 freeze-thaw cycles,the strength loss rate is within 1 8%,and no obvious cracks are generated on the surface.In the 180d long-term immersion test,under the dosage of 40%tailings,the final compressive strength of lightweight soil with wet density of 600kg/m3,700kg/m3 and 800kg/m3 is 1.09MPa,1.38MPa and 2.16MPa respectively,which has good water stability.(4)The pore structure of lightweight soil was studied by image analysis method,and the results show that among the pore structure parameters,porosity,average pore size and roundness are positively correlated with tailings content.The pore size distribution of tailingsslag-carbide slag foam lightweight soil is basically between 0-0.4mm.When the tailings content is greater than 30%,pores with pore size greater than 1mm begin to appear.The pore structure parameters are negatively correlated with the wet density.