Research And Application Of Backfilling Cementing Material For Mine Industry

Cemented backfilling is an important part of scientific mining;it can not only effectively alleviate or prevent surrounding rock mass movement and subsidence,but also realize the sustainable development of mineral resources.However,the high filling cost restricts the application of mine filling technology.Steel slag,fly ash and blast-furnace slag are three kinds of major industrial wastes,which have potential hydration performance.Cementing material from these industrial wastes possesses the characteristics of energy saving and low environment load,and has become hotspot in recent years.Based on the idea of synergistic effect,two kinds of cementing materials are designed considering resources and regional conditions: steel slag/blast-furnace slag cementing material and fly ash/blast-furnace slag based cementing material.The aim is to reduce cost and increase filling benefit.First,the cementing activity of steel slag and blast furnace slag was activated by mechanical grinding and chemical excitation.Desulphurization gypsum,calcium chloride and carbide slag were used to control the hydration products and enhance hydration of steel slag and blast furnace slag.Consequently,a kind of cementing material with steel slag and blast-furnace slag for total tailings paste backfill was prepared.The mass proportioning of the cementing material is:steel slag 35.5 %,blast furnace slag 35.5 %,Portland cement 10 % and mineral control agent 19 %.The compressive strength of the cementing material of 28 d reaches 29.47 MPa.The hydration products and strength adjusting mechanism were analyzed using XRD and SEM.The results show that the major hydration products which contribute for the mechanical strength of the cementing material are hydrated calcium silicates and ettringite.Proper proportioning of the adjustment agents enhances the hydration of steel slag and blast furnace slag and optimizes the hydration products.Second,based on activation and synergistic effect among various materials,a low-cost mine backfill cementing material was prepared from fly ash,granulated blast-furnace slag,carbide slag and compound activator.The proper proportioning of cementing material is obtained by response surface optimization method: fly ash 60 %,blast furnace slag 20 %,carbide slag 10 % and compound activators 10 %.The hydration products were analyzed by using XRD and SEM.The results show that the major products of cementing material are hydrated calcium silicates,hydrated aluminate calcium,ettringites and zeolite-like materials.In order to study the cementing effect of the two kinds of cementing materials on tailings,effects of cement-sand ratio,mortar density and curing time on the strength of filling body are investigated.The results show that under the condition of the mass ratio of steel slag/blast-furnace slag blend cementing material and tailings 1:4~1:8,and the concentration of total solid 67 %~73 %,the compressive strength of total tailings filling body at 28 d is up to 1.53~5.24 MPa.Under the same condition,the compressive strength values of fly ash/blast-furnace slag cementing material based filling body at 28 d reaches 0.68~2.63 MPa.Adjusting the material proportioning can obtain different cementing materials to satisfy the requirements of different mined-out areas.The results show that the mechanical strength of steel slag/blast-furnace slag cementing material filling body is much higher than that of Portland cement filling body.At high slurry concentration and low mortar ratio,the required dosage of fly ash/ blast-furnace based cementing material is significantly lower than Portland cement,which means that its consolidation ability is better than Portland cement.The economic analysis of two kinds of cementing materials was carried out.Compared to Portland cement,the filling body of waste residue based cementing material has higher performance and lower cost.Furthermore,the cementing material can be selected according to the raw material source,transportation distance and filling requirements.In this work,steel slag,fly ash,blast-furnace slag were used as raw material,activated with calcium carbide slag,and desulfurization gypsum etc.,to prepare cost-effective cementing material to substitute Portland cement in backfill of mine.It not only solved the problems of solid waste storage and environmental pollution,but also realizes rational use of materials,and possesses has high economic and environmental benefits.