煤系固废基绿色充填材料制备及其性能研究

Preparation of coal-series solid-waste-based green filling materials and their performance

充填技术是绿色开采的重要组成部分,研发成本低廉、性能可靠、低碳环保的充填材料,是发展充填技术的关键。采用煤矸石(CG)和煤系偏高岭土(MK)为原材料制备煤系固废基绿色充填材料,探讨配合比和碱激发剂对充填材料强度以及流动度的影响,并结合X射线衍射(XRD)、傅里叶变换红外吸收光谱仪(FTIR)、热重分析(TG)和扫描电镜能谱分析(SEM-EDS)等表征手段,揭示充填强度发展机理。综合强度、流动性和环境指标,优化充填材料配比。研究结果表明:绿色充填材料体系中,煤系偏高岭土通过碱激发水化反应起到胶凝作用,体系强度随偏高岭土的增加呈线性增长,磨细的煤矸石充当惰性填料,协同Na_(2)SiO_(3)改善流动性。该充填材料主要水化产物为N―A―S―H和沸石,Si―O―Si发生聚解,随即四面体Al―O键部分取代Si―O键,由(SiO_(4))^(4−)变成(AlO_(4))^(4−),进一步聚合形成Si―O―Al基团。当碱激发剂中Na_(2)SiO_(3)与NaOH比例为1∶1时,聚合程度最高。水化产物填充了煤矸石颗粒间孔隙,使基质致密,提高充填材料强度。综合指标评价推荐偏高岭土与煤矸石的配比为3∶7,此时不仅满足强度和流动性的要求,而且碳排放指数仅有0.257。本研究为开发成本低廉、性能可靠、低碳环保的充填材料提供新的思路,具有较好的实用性和经济性。

The filling technology is an important part of green mining.The low-carbon environmental-friendly filling materials with low costs in research and development and reliable performance are critical for the development of filling technologies.The coal gangue(CG)and coal-series metakaolin(MK)were adopted as the raw materials to prepare coal-series solid-waste-base green filling materials,and the effect of the mixing proportion and alkali activator on the strength and fluidity of filling materials was discussed.In combination with the X-ray diffraction(XRD),Fourier-transform infrared spectroscopy(FTIR),thermogravimetric(TG)analysis and scanning electron microscopy/energy dispersive x-ray spectroscopy(SEM-EDS)and other characterization measures,the filling strength development mechanism was revealed.Considering the strength,fluidity and environmental indexes,the mixing proportion of filling materials was optimized.As indicated by the research results,in the green filling material system,the coal-series metakaolin generates gelatinization effects through alkali-activated hydration reaction.The system strength is increased in a linear mode with the increase of metakaolin.The finely-grounded coal gangue is used as the inert filler that coordinates with Na_(2)SiO_(3) to improve fluidity.The main hydration products of this filling material are N―A―S―H and zeolites.Right after Si―O―Si depolymerization,the tetrahedral Al―O bond takes the place of Si―O bond,resulting in the change of(SiO_(4))^(4−)into(AlO_(4))^(4−).Through further polymerization,the Si―O―Al group is generated.When the ratio between Na_(2)SiO_(3) and NaOH is 1∶1 in the alkali activator,the polymerization degree is the highest.The hydration products are filled into the pores of coal gangue particles,leading to dense matrix and stronger filling materials.As recommended based on the comprehens-ive index evaluation,the mixing ratio between metakaolin and coal gangue shall be 3∶7,which does not only meet the requirements of strength and fluidity but also provides the carbon emission index as low as 0.257.This research provides new approaches for developing the low-carbon environmental-friendly filling materials with low costs and reliable per-formance,and is highly practical and economically efficient.