Research And Application Of Ecological Cementitious Materials In Mine Filling Engineering

At present,the common way to deal with mine tailings is to make up tailings backfill to fill the mined-out area,which not only improves the ore recovery rate but also ensures the stability of the underground working environment.Meanwhile,it enables the recovery and utilization of tailings solid waste.The tailings of a lead-zinc mine were treated by cyclone to obtain classified tailings and fine tailings.Among them,the classified tailings can be cemented with cement for mine filling,but the properties of the backfill cannot meet the requirements of filling production very well.The cement cost is increasing day by day,and the filling cost is high.More than 90% of the particle size of fine tailings is less than 100 um,which is difficult to be reused,so it is discharged to the tailings pond for storage.Aiming at the filling problems faced by a lead-zinc mine,combined with the existing situation of solid waste resources in the surrounding environment,the research work is carried out,aiming at developing cementitious materials to replace cement filling.It aims to solve the mine tailings depot withdrawal and improve the surrounding ecological environment.Based on the field investigation and theoretical analysis,the alkali excitation system of slag partially replacing cement was selected,and the cementation mechanism and performance advantages of cementitious materials and backfills were studied by means of XRD,SEM,and microcalorimetry.Finally,field industrial test was carried out to verify its feasibility in the actual filling.At the same time,to study the effect of fine tailings on the performance of the new cementitious material system,the classified tailings were partially replaced by the fine tailings to make up the fillings for preliminary tests.Research shows:1)In the system of partially replacing cement with slag,adding proper amount of sodium sulfate can accelerate the hydration reaction rate of the system and release the active ingredient of slag,so that the system can produce more C-S-H hydrates and other hydration products in the early hydration process.In this way,we could shorten the setting time and improving the early strength of the backfill.2)Laboratory tests and field industrial tests show that the flow performance index,strength index,and later durability index of the backfill made of ecological cementitious material and classified tailings can meet the mine requirements.At the same time,choosing appropriate filling ratio parameters to prepare backfill which meets different types of goaf can reduce the consumption of single cementitious material of backfill.3)The improvement of filling preparation technology can improve the mechanical properties of backfill to a certain extent.At different mixing rates,the early strength of the samples with high mixing rates was significantly improved compared with that of the samples with low mixing rates,and the cement system and the ecological cementitious material system showed the same law.4)The use of fine tailings instead of 20% classified tailings reduces the flow properties of the backfill and improves the mechanical properties.With the increase of the number of fine tailings in the backfill,the fluidity of the backfill showed a downward trend within a specific range,and the 7d and 28 d compressive strength of the backfill was further improved.5)The filling effect of industrial test is good.According to the data record of industrial test,comparing with the cost of cement filling,the cost of ecological cementitious material used in the single filling of glue surface and room is 29% and 12% less than that of cement respectively.