Study On Preparation And Properties Of Refining Slag Based Filling Cementitious Material

The backfill mining method is the most effective way to control the goaf.It has the advantages of high ore recovery rate,safe operation and strong adaptability and more and more widely used.However,at present,most filling cementitious materials are cement,which has the problem of high filling cost.Refining slag is the waste slag discharged from the refining process of the steel industry,and its utilization rate is low at present.With the continuous promotion of the circular development mode of green economy in China,the low-efficiency utilization of refining slag has become an important obstacle to the green development of iron and steel enterprises.Improving the resource utilization efficiency of refining slag is one of the difficult problems that iron and steel enterprises must solve at present.Using solid waste synergy to prepare mine filling cementitious materials instead of cement has become a research hotspot.Therefore,this paper takes the refining slag as the main research object,systematically studied the grinding characteristics and cementitious properties of the refining slag,used the refining slag to prepare the cementitious material for the filling of all solid waste mines,analyzed the hydration mechanism of the cementitious material,and tested the properties of the filling body.The main conclusions are as follows:The research shows that after mechanical grinding,the fineness of refining slag decreases,the specific surface area increases,and the grinding efficiency decreases gradually with the extension of grinding time.The optimal grinding time is 80 min and the specific surface area is 595 m²/kg.Refining slag mainly contains C₁₂A₇,C₃AH₆ and other mineral phases.Mechanical grinding will not change the mineral composition of refining slag,but the crystal structure will be damaged and distorted,the macro cracks will be reduced,and the spherical like particles will be increased.The results of mortar show that the activity index of refining slag milled for 80 min can reach 84%,the fluidity ratio is 93%,the standard consistency is 27.5%,the initial setting time is 27 min,and the final setting time is 31 min.the stability is good.The refining slag itself has certain hydration properties,and its hydration products are mainly C₄AH₁₃,C₃AH₆,CH and gel.Using refining slag,blast furnace slag,and desulfurization gypsum as raw materials,the optimal proportion of ternary non-clinker solid waste mine filling cementitious materials was developed through the proportioning test:refining slag 30%,slag 46%and desulfurization gypsum 24%.The compressive strengths of the blocks at 3 d,7 d,and 28 d were 1.00 MPa,3.08 MPa,and 7.35 MPa,respectively,which were 0.73 times,1.25 times,and 1.52 times that of the cement-filled test blocks under the same conditions.The hydration products of refining slag-blast furnace slag-desulfurized gypsum cementitious materials are mainly needle-shaped ettringite and C-S-H gel.With the extension of curing age,the hydration products increase continuously,filling body forms dense paste,and provides strength for hardened paste.By adjusting the concentration and lime-sand ratio,the 28-day compressive strengths of Yunjialing filling and Zhongguan iron ore filling materials can be controlled at 1.09-8.73 MPa and 0.71-5.41 MPa,respectively,which meet different requirements.The setting time of filling materials shall not exceed 24 hours,and the bleeding rate shall be about 5%.In actual production,the filling slurry concentration shall be increased and the cement sand ratio shall be reduced as much as possible to ensure the filling quality and reduce the cost.The temperature is conducive to the growth of the compressive strength of the refining slag-based backfill.The growth rates of the compressive strength at 3 d,7 d and 28 d are 367%,170%and 46%,respectively.The preparation of mine filling cementitious material instead of cement with refining slag,slag and desulfurized gypsum solves the problems of high mine filling cost and low economic benefit.Moreover,it meets the requirements of low-carbon and waste-free development,protecting and improving the environment,and improving the utilization rate of solid waste,and has a broad market application prospect.