| With the rapid development of tungsten industry,the production of tungsten tailings will gradually increase.A large number of tungsten tailings occupied land area,endangering human health,causing great security risks to the environment,also seriously restricted the development of tungsten industry.Therefore,the utilization of tungsten tailings is imperative.On the other hand,geopolymer is a popular research material in recent years,and many excellent properties make it have wide application prospect.In this paper,on the basis of the study of the characteristics of tungsten tailings,the modified method was used to prepare geopolyme,specific content and results are as follows:(1)The modified tungsten tailings were prepared by pretreatment of alkali-heat-ball milling.The properties of modified tungsten tailings were analyzed,including chemical composition,phase composition and particle size distribution.The results show that the modified tungsten tailings are improved and suitable as raw materials for geopolymer.Curing system determined as follows: the curing pressure was 1.0MPa,the curing time was 2h,the pressure relief time was 30 min,the 7 days compressive strength of geopolymer sample prepared in this condition was 26.62 MPa.XRD,FTIR and SEM analysis show that under the autoclave,geopolymer sample is mainly composed of amorphous material,Al enters Si-O-Si structure,the degree of polymerization is more thorough and the structure is dense.(2)Geopolymer precursor was prepared by adding NaOH,Na2CO3,KOH,K2CO3 to the tungsten tailings、calcining at 500℃,650℃,800℃and adding 15% powdered sodium silicate,geo polymer samples were prepared according to the liquid-to-solid ratio 0.12 and then curing at room temperature or a high temperature of 70 ℃ with moisture,respectively.The results showed that the solid reaction precursors have good activity which calcined at 800℃C using KOH as auxiliarieswere,geopolymer samples had a compressive strength of 15.41 MPa for 7 days.XRD,FTIR and SEM analysis showed that the Si-O-Si structure changed to the Si-O-Al structure,the sample structure is uniform and the degree of compactness is better.It has also been found that high temperature and moisture conservation hinders the progress of polymerization,which is not conducive to the development of compressive strength.(3)The frost resistance of the tungsten tailings based geopolymer was studied,The results show that when the silica fume content is 15%,the liquid to solid ratio is 0.25 and the molding pressure is 20 MPa,geopolymer sample has the best frost resistance,Freeze-thaw cycles up to 70 times When the mass loss rate is 5%,the compressive strength loss rate is only 12.77%.The number of freeze-thaw cycles more,the compressive strength loss rate is small.hence,the frost resistance is better.SEM analysis showed that the freeze-thaw cycle had some damage to the structure of the sample and the gel fraction was reduced.(4)The thermal stability of the tungsten tailings based geopolymer was investigated.The effects of aggregate content and gradation on the thermal stability of the samples were investigated.The results show that the compressive strength of geopolymer sample at 1000℃is 2.44 times then which at room temperature when the aggregate content is 50%,20-60 mesh and 60-100 mesh each account for 50%.Hence,the thermal stability is better.XRD,FTIR and SEM analysis showed that the phase composition of geopolymer samples did not change obviously at high temperature,a small amount of Si-O-Al structure changed to Si-O-Si structure,the micrometite content decreased,and the overall structure of the sample did not change significantly.In summary,the tailings of geopolymer has excellent frost resistance and thermal stability,using tungsten tailings prepared geopolymer has a certain feasibility,but the compressive strength of samples is generally low,improving the comprehensive performance of tungsten tailings remains to be further studied. |
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