| In view of the problems of high backfill cost and material shortage in paste backfill mining,it is necessary to actively seek new solid waste cementing materials with excellent performance and environmental protection to replace cement products,so as to reduce the cost of mine backfill.Magnesium smelting process was numerically simulated in this paper,choose to produce magnesium slag in the process of material,on the basis of through source modified industrial test to obtain high hydration activity of magnesium slag pulverization,hardness,and large pieces of slag,mine of preparation is given priority to with modified magnesium slag gelled material,from bulk solid waste resources recycling,environmental protection and solid waste disposal together more as a starting point,the preparation of all solid waste paste backfill material.The modified magnesium slag-based composite cementing material was successfully prepared through laboratory tests.On this basis,the ratio optimization of modified magnesium slag-based cemented coal gangue backfill material(MCGB)was carried out,and its mechanical properties and flow characteristics were experimentally studied.The backfill industrial test demonstration project was carried out and successfully applied in mahuangliang coal mine.Therefore,the research and development of the new mining composite cementing material not only improves the utilization rate of bulk solid waste such as coal gangue and fly ash,but also realizes the green and harmless strip backfill mining for mahuangliang coal mine,which has good economic benefits,environmental effects and social effects.Based on modified magnesium slag,modified magnesium slag-based mining composite cementification material was prepared in this paper.Through the analysis and research of macro test,micro test,field industrial test and other technical means,the main conclusions are as follows:(1)Modified magnesium slag has similar chemical composition and mineral phase(βC2S)to portland cement,which can completely replace portland cement for backfill goaf,and is a potential new type of cementing material for mining.(2)Binary mineral compound cementitious material prepared by using modified magnesium slag and fly ash,due to the hydrolysis of modified magnesium slag itself produces a large number of alkaline hydration products,inducing fly ash to undergo pozzolanic reaction,forming a multi-ion reaction system rich in SiO44-、Ca2+、HSiO43-and so on to participate in hydration reaction.The hydration products mainly composed of C-S-H gel,Ca(OH)2,AFt(AFm)and other silicates are generated.The uniaxial compressive strength of the net slurry sample after curing for 28 days is more than 10MPa,which is completely suitable for mine backfill and can also be co-treated with coal gangue,which has good economic benefits.(3)The uniaxial compressive strength of MCGB sample at 28 days curing is over 2.761MPa,the highest compressive strength is as high as 5.884MPa,the standard slump is over 19cm,the bleeding rate is between 1.27 and 4.82%,and the pumping time is over 4 hours.All the basic indexes meet the requirements of strength and fluidity of mine backfill.Secondly,the compressive strength of MCGB samples at different ages increases with the increase of modified magnesium slag content,and increases first and then decreases with the increase of fly ash content.(4)In the application of backfill industrial test and demonstration engineering in mahuangliang coal mine,there is no obvious layering of the new mixing backfill slurry after standing for 2～4 hours,the standard slump is more than 180mm,the bleeding rate of the slurry is less than 3%,and the uniaxial compressive strength of the backfill body after curing for 28 days is 6.23MPa,which fully meets the requirements of strength and fluidity of backfill in mahuangliang coal mine.Compared with ordinary portland cement used for mine backfill,the use of this new cementing material can save more than 46 million yuan of backfill cost for mahuangliang coal mine every year at least. |
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