Study On The Performance Of Tailings Backfill Prepared From Lead-zinc Smelting Slag Based Binder

Industrial waste still troubles the development of non-ferrous metal mining industry.Non-ferrous metal mines produce a large amount of smelting slag and tailings every year.The accumulation of these industrial wastes not only causes great pressure on land resources,but also is a waste of resources.Lead-zinc smelting slag contains certain activity,but the main treatment method is still stacking,and its resource utilization has limitations such as high energy consumption,low mixing amount and secondary waste output.The cemented filling can quickly absorb tailings and ensure the safety of mining,but the cost of cementation is high,and has the limitations of low strength in early stage and low utilization rate of fine tailings.In view of the above situation,the basic physical and chemical properties of smelting slag were studied in this paper.Following the principle of proximity,a new environment-friendly material was prepared to replace cement as cementing filling by taking a large amount of lead and zinc smelting slag combined with blast furnace slag（GGBFS）and cement as a ternary system,and alkali and sulfate were used to stimulate it.The properties and mechanism of cementing materials and backfill were studied by adjusting macroscopic indexes and microscopic analysis.Finally,the cementing material and backfill were combined with fine-grained tailings to absorb solid waste as much as possible.The research results are as follows:（1）The main components of lead-zinc smelting slag are Fe₂O₃,Ca O,and Si O₂.The content of iron inside is high,the appearance is black,the density is larger,the particles are small and irregular in shape,and the particle size distribution is uniform,which is similar to cement mineral powder.It contains a lot of vitreous body inside,but as a cement mixture,its activity is not high,so it needs to be further modified and stimulated.（2）In the binder,the incorporation of sulfate can significantly improve the early strength of the binder,and the incorporation of sodium sulfate can improve the late strength of the binder.The addition of sodium carbonate can improve the early strength of the binder,while the addition of other alkali activators can weaken the strength of the system in different degrees.The increase of cement powder ratio is followed by the increase of strength and the decrease of flow property.The optimal cement powder ratio is 9:1,and the appropriate sodium sulfate content can increase the compressive strength and flow property of the binder in the whole age.When the sodium sulfate content is 2%,the binder property is the best.The morphology and phase analysis showed that the main products were C-S-H gel,ettringite,Ca（OH）₂and so on.（3）In the filling body,the increase of cement/GGBFS ratio will weaken the early strength of the filling system and reduce the flow performance of the filling body,and the optimal cement/GGBFS ratio is 3:7;The influence of sodium sulfate is similar to that of binder and its main products are ettringite,C-S-H gel and calcite.The increase of the binder-sand ratio can effectively improve the compressive strength,flow performance and dehydration performance of the filling body.The increase of filling concentration can improve the compressive strength of the filling body,but it will reduce the flow performance and dehydration performance of the filling body.The water-binder ratio affects the compressive performance of the backfill more,while the water-sand ratio affects the flow performance and dehydration rate.The addition of fine-grained tailings can significantly reduce the compressive strength and flow performance of the backfill.At a low binder sand ratio,the compressive strength of the backfill with 30%fine-grained tailings is higher than that with 20%tailings,and this gap gradually increases with the increase of age.（4）The new cementified material backfill has certain advantages over the cement backfill in terms of flow value and compressive strength.When the cementified sand ratio is1:3 and the filling concentration is 76%,the working performance of the new cementified material backfill meets the requirements of the first layer of the mine rubber surface;when the cementified sand ratio is 1:7 and the filling concentration is 74%,the working performance of the backfill body meets the requirements of the mine room pouring.The working performance of the filling body with cement-sand ratio of 1:7,filling concentration of 70%and fine-grained tailings content of 30%can meet the requirements of column pouring between mines.