Preparation And Mechanical Properties Of Low-activity Copper Smelting Slag Filling Cementitious Materia

A large number of goafs formed during the mining process,as well as tailings and smelting slag left after smelting,have seriously damaged the ecological environment of the mining area.Fill-and-fill mining method has been widely used because of its advantages of high recovery rate,low dilution rate,effective control of ground pressure and surface subsidence.The preparation of mine filling cementitious materials based on nonferrous smelting slag will be an urgent need for the development of"waste to control harm",this paper stimulates the activity of copper smelting slag by adding different chemical initiators and other mineral admixtures to stimulate its activity to generate gelitious hydration products,and at the same time uses XRD,SEM,EDS and ICP to analyze the hydration mechanism,and conducts in-depth research on the excitation mechanism of cementitious activity of copper smelting slag.Through the optimization of the ratio of cementitious materials,a feasible ratio scheme was obtained,which was applied to the cementation filling system of the whole tailing sand in mines.The main research results are as follows:1)The chemical composition,composition content and mineral composition of copper smelting slag under different grades are obviously different,the metal elements and their oxides in the copper smelting slag mainly include Fe₂O₃,Ca O,Al₂O₃,Mg O,non-metallic elements and their oxides are mainly Si O₂,and the main mineral composition in copper smelting slag is iron olivine.2)After the physical activation of the copper smelting slag,the hydrated copper smelting slag specimen has a certain strength,but the strength is low,and then four different contents of cement clinker,gypsum powder,sodium hydroxide and hydrated lime are selected to compound activate the copper smelting slag,and the highest compressive strength of the composite cementitious material specimen body is32.7MPa.In this composite cementitious material,the comprehensive utilization rate of copper smelting slag has reached 70%.3)The microstructure and cementation mechanism of composite cementitious material specimens and tailing-containing fillers can be analyzed:the addition of cement clinker provides the necessary chemical environment for the chemical reaction in the early stage of slurry,and the addition of hydrated lime,gypsum and sodium hydroxide provides more calcium ions and hydroxide ions for the hydration reaction,further stimulating the cementation activity of copper smelting slag,and continues with the hydration process.The connection between copper smelting slag particles and hydration products makes the whole system closer,and then more flocculent C-S-H gels and needle-like calcium alum and other substances are generated,and overlap with each other to form a firm and dense space system,so that the specimen body forms higher strength.4)Through the compressive strength test,the composite cementitious material was compared and analyzed with the tailings backfill and P·O42.5 Tailings cement and its influencing factors.The results show that under the same conditions,the strength and stability of copper smelting slag-based cementitious materials are almost the same as those of P·O42.5 Cement backfill,which can be partially used instead of cement in goafs.5)Dissolution behavior of heavy metals Cu²⁺,Zn^2+,As²⁺,etc.under different dissolution times and p H of copper smelting slag composite cementitious material specimens and filling body specimens containing tailings:With the increase of dissolution time and the increase of p H value,the dissolution amount of heavy metals in copper smelting slag composite cementitious material specimens and filling body specimens decreases accordingly,and the prepared composite cementitious materials have a certain solidification effect on heavy metals,which is conducive to controlling the possible pollution of groundwater.