Research On Application Of Phosphorus Tailings Pavement Base Material

Phosphorus tailings are the industrial solid wastes formed by the flotation of phosphate rock.In order to improve the comprehensive utilization rate of phosphorus tailings,the application research of phosphorus tailings pavement base material was put forward.In the study,the discrete element model is established to design and evaluate the mixture gradation of phosphorus tailings instead of sand and filler,and the cement stabilized phosphorus tailings waste rock and industrial waste slag comprehensively stabilized phosphorus tailings waste rock pavement base materials are designed.The mechanical properties,durability and Ion Leaching Properties of pavement base materials are evaluated through indoor tests,and the test sections are built for practical application.The results show that:(1)The mineral composition of phosphorus tailings is mainly dolomite,and contains a certain amount of quartz and fluoroapatite,which has good particle strength and chemical stability.(2)Using the discrete element software PFC3 D to establish the model,the calculated voids of the main skeleton are in good agreement with the results obtained from the compaction experiment,and the minimum voids of the optimal coarse aggregate of the main skeleton are 30.44%.By analyzing the effect of filling the voids of graded waste rock with different mass fractions of phosphorus tailings,when the mass fraction of phosphorus tailings()is less than 23%,the mixture of phosphorus tailings and waste rock belongs to skeleton void structure;When the mass fraction of phosphorus tailings()is in the range of 23～30%,the mixture of phosphorus tailings and waste rock belongs to skeleton dense structure;When the mass fraction of phosphorus tailings()is greater than 30%,the phosphorus tailings waste rock mixture belongs to suspension dense structure.The skeleton dense structure with the best mixture grading has better road performance,However,the suspension dense base material has low cost,large amount of phosphorus tailings and good road performance,so it has better popularization and application value.(3)In cement stabilized phosphorus tailings waste rock base course materials,phosphorus slag powder has particle filling effect,pozzolanic activity and retarding effect on cement.When the content of phosphorous slag powder is 6%,the unconfined compressive strength of phosphorous tailings waste rock stabilized by cement phosphorous slag powder reaches the best in 7 days.In the later stage,the pozzolanic reaction of phosphorus slag powder continues to occur,forming hydrated calcium silicate gel,ettringite and other cementing products,which makes the mixture structure more compact,is conducive to the later strength growth,and has good durability.(4)In the whole industrial waste residue stabilized phosphorus tailings-waste rock base material system,the mechanical properties of pavement base material first increase and then decrease with the mass ratio of calcium carbide slag and phosphorus slag powder.When calcium carbide slag: phosphorus slag powder = 1:2,calcium carbide slag phosphorus slag powder stabilized phosphorus tailings-waste rock pavement base material has the best mechanical properties.When fly ash is added instead of phosphorus slag powder,the early strength of calcium carbide slag-phosphorus slag-fly ash stabilized phosphorus tailings waste stone pavement base material increases with the increase of fly ash content,but the pozzolanic activity of fly ash in the later stage is not as good as that of phosphorus slag powder,and the later mechanical performance of pavement base increases with the increase of phosphorus slag powder content,The ion leaching characteristics of the whole industrial waste residue stabilized phosphorus tailings waste rock base material meet the standard requirements.(5)Carry out the practical application of cement stabilized phosphorus tailings waste rock pavement base material,and disperse the phosphorus tailings before mixing the mixture,which will help to mix the mixture of pavement base material evenly and make the construction section meet the technical requirements;The pavement base material has good integrity,no crack on the surface and high bearing capacity;As the base material of pavement,phosphorus tailings can use a large amount of industrial solid waste,so as to save the construction cost and have good social and economic benefits.