Study On Preparation And Environmental Behavior Of Filling Cementitious Materials Based On Copper And Nickel Smelting Slag

In the process of mining and smelting of non-ferrous metals,a large area of goaf will be left underground.The existence of mined-out areas will cause unbalanced ground pressure and damage to the environment,and also threaten the safety of workers.At the same time,many solid wastes will be produced when the ore was mined and smelted.At this stage,burial and storage are the treatment methods of the solid waste.This not only land area is occupied,but also harmful elements in solid waste can seep into the ground through surface runoff due to rain erosion and other reasons,which is a threat to environment.Therefore,it is urgent to strengthen environmental protection and comprehensive utilization of mineral resources through green mining.Filling mining technology is the main supporting technology of green mining.The high strength of the filling cementitious material can be stably pressed,and the source of its raw materials is wide,and solid waste in the mining area can be selected as an aggregate or cement substitute.The development and application of solid waste-based filling cementitious materials are of great significance to environmental governance in mining areas.However,in actual work,the filling cementitious material usually fails to connect to the top due to bleeding and shrinkage.Therefore,the roof-contacted filling problem has also become the focus of people's attention.In this paper,the copper-nickel smelting slag-based filling cementitious materials and filling cementitious expansion materials were prepared and their mechanical properties and the environmental behavior were explored.In this study,the influence law and mechanism of the sand-cement ratio on the strength of cementitious filling materials were discussed.The effects of sand-to-cement ratio,additives and foaming agents on the filling cementitious expansion materials were studied,and the best process parameters of the expansion materials are selected from the test results of strength and porosity.And the influence mechanism of each condition was analyzed through composition,density and morphology.The compressive strength of the filling cementitious expansion material was prepared under optimized technological conditions is 1.43 MPa.The porosity is 65.9%and the utilization rate of smelting slag is 70%.Not only the effective use of smelting slag was guaranteed by the material prepared,but the filling efficiency was ensured due to the excellent expansion efficiency.A new evaluation methodology was used to study the leaching behavior of harmful elements of two smelting slag-based cementitious materials.By adjusting the pH value of the leaching solution,the influence of the neutralization reaction of the cementing agent and the acid on the leaching of harmful elements is reduced.The leaching law of filling cementitious material and filling cementitious expansion material under multiple conditions were studied through setting up multiple sets of experiments.The results show that the cementitious material can effectively cure the harmful elements.And it is less affected by the environment.It proves that the cementitious material prepared has good stability.It is beneficial to control the pollution of the environment in the mining area by harmful elements in the smelting slag.