| The cemented tailings backfill has been widely applied since mining activities have shifted into deeper areas and the increasing attention of the state to safety and environmental protection.The cemented tailings backfill with cement as cementing material,especially the cemented superfine tailings backfill,has poor curing effect and high cost.The development of low-cost green filling cementitious material suitable for superfine tailings aggregate is not only the key to realize mine safety,high efficiency and low-cost mining,but also the common demand faced by more and more mines.In view of the technical and economic problems faced by the cemented superfine tailings backfill in Zhongguan iron mine,based on the concept of "treating disasters with waste",this paper carried out the experimental research on the application of slag based cementitious material for the cemented superfine tailings backfill by using the metallurgical slag in Xingtai and Handan area on the basis of the development of consolidation powder in the early stage.In order to further reduce the cost of cementitious material,steel slag was used to replace cement clinker and cooperate with slag and other solid waste resources to develop steel slag based cementitious material suitable for cemented superfine tailings backfill.The strength of backfill,slurry pipeline transportation and rheological properties of steel slag based cementitious materials were studied.On the basis of determining the reasonable strength,the slurry ratio was optimized.and the industrial filling test was carried out,which laid the foundation for the large-scale industrial application of steel slag based cementitious materials in Zhongguan iron mine.The following works were carried out:(1)The physicochemical properties of test materials including slag,steel slag,desulfurization gypsum and tailings were analyzed,Based on the previous research,alkali activated,salt activated and alkali-salt compound activated slag based cementitious materials suitable for cemented superfine tailings backfill were carried out respectively.The optimal ratio was determined as follows:10%cement clinker,15%desulfurization gypsum and 75%slag powder.(2)On the basis of the development of slag based cementitious materials,steel slag was used to replace cement clinker and part of slag,the proportioning tests of steel slag based cementitious material suitable for cemented superfine tailings backfill was carried out,and the BP neural network was used for prediction and optimization,and a steel slag based cementitious material with "No clinker and less slag"was developed,and the optimal proportion was determined as follows:30%steel slag powder,16%desulfurized gypsum and 54%slag powder.On this basis,the hydration reaction process,hydration product types and microstructure of steel slag based cementitious materials were explored,through micro tests,and the synergistic excitation mechanism was proposed,and the reason why there was no swelling instability of steel slag based cementitious materials was explained from different angles.(3)The application of steel slag based cementitious material for cemented superfine tailings backfill was studied.Compared with P.O 42.5 cement,the tests of mortar strength,slurry pipeline transportation characteristics and rheological characteristics were carried out respectively,and their influence laws were analyzed.the results show that steel slag based cementitious material is superior to cement in filling strength,slurry fluidity and stability under the same conditions.And Fluent software was used to simulate the slurry pipeline flow law under the actual filling concentration and flow rate,and then the variation laws of pipeline pressure,flow rate and resistance along the way were revealed.(4)According to the geological conditions and subsequent filling status of Zhongguan iron mine,the energy dissipation relationship between cemented backfill and ore rock was analyzed based on the interaction between cemented filling body and ore rock.Based on the energy matching relationship,the reasonable strength of one-step and two-step filling for 28d was determined to be no less than 2.50MPa and 1.0MPa,respectively.On this basis,combined with the results of slurry pipeline transportation characteristics,The preparation parameters of filling slurry were optimized by using fuzzy optimization decision theory,The optimal ratio of filling slurry with steel slag based cementitious material as follows:the cement sand ratio was 1:5 and the slurry mass concentration was 64%.The industrial test was carried out by the filling system of Zhongguan iron mine,The results of core-drilling sampling show that the strength of steel slag based cementitious material superfine tailings backfill meets the strength requirements of Zhongguan iron mine,has good stability,and has significant economic and environmental benefits compared with cement and slag based cementitious materials,which lays a foundation for large-scale industrial application of steel slag based cementitious material and realization of safe,efficient and low-cost mining in mine. |
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