煤矸石基胶结充填体力学性能及微观结构演化研究

Study on Mechanical Properties and Microstructure Evolution of Coal Gangue-based Cemented Backfill

针对某煤矿矸石消纳量低、处置成本高等技术瓶颈,为契合两山论及绿色矿山发展理念,研究以煤矸石为骨料,大宗工业固废粉煤灰和脱硫石膏等制备胶凝材料,研制煤矸石基新型复合膏体充填材料。借助正交试验,设计以细矸率、煤矸石掺量、粉煤灰掺量为目标因素,考察不同因素水平变化下充填体力学强度的影响规律,综合极差分析和方差分析,定量评估各因素对充填体样品强度的敏感程度,采用压汞仪、扫描电子显微镜揭示了水化产物作用机理、孔结构特征及微观结构形貌。结果表明:①随着细矸率的提升,充填体样品的抗压强度和抗折强度均表现为先正相关后负相关,细矸率40%是其性能临界点;煤矸石掺量影响充填体样品力学强度的规律为先增后减;随着粉煤灰掺量的提升,充填体样品早期强度降低,后期强度升高。②充填体样品3d和7d强度的影响因素显著性强弱的排序为细矸率、煤矸石掺量、粉煤灰掺量,最优配合比为细矸率40%、煤矸石掺量40%、粉煤灰掺量25%;充填体样品28d强度的影响因素显著性强弱的排序为细矸率、粉煤灰掺量、煤矸石掺量,最优配合比为细矸率40%、煤矸石掺量45%、粉煤灰掺量40%。③充填材料主要水化产物为钙矾石和C—S—H凝胶,二者的搭接密实性决定了充填体样品强度的发展;随着水化龄期的延长,水化产物不断发育,相互搭接形成致密的网状结构,细化结构孔洞,显著提高了充填体样品的力学强度。

In view of the technical bottlenecks of low consumption and high disposal cost of gangue in a coal mine,in order to fit the two mountains theory and the concept of green mine development,this paper studies the preparation of cementitious materials with coal gangue as aggregate,large industrial solid waste fly ash and desulfurization gypsum,and develops a new type of coal gangue-based composite paste filling material.With the help of orthogonal test,the design takes the fine gangue rate,coal gangue content and fly ash content as the target factors to investigate the influence law of the mechanical strength of the filling body under different factor levels.Comprehensive range analysis and variance analysis are used to quantitatively evaluate the sensitivity of each factor to the strength of the filling body sample.Mercury porosimeter and scanning electron microscope were used to reveal the mechanism of hydration products,pore structure characteristics and microstructure morphology.The results show that:①with the increase of fine gangue rate,the compressive strength and flexural strength of the filling body samples show a positive correlation and then a negative correlation,and the fine gangue rate of 40%is the critical point of its performance.The influence of coal gangue content on the mechanical strength of filling body samples is first increased and then decreased.With the increase of fly ash content,the early strength of backfill samples decreases and the later strength increases.②The order of the significance of the influencing factors of 3 d and 7 d strength of filling body samples is fine gangue rate,coal gangue content and fly ash content.The optimal mix ratio is 40%of the fine gangue rate,40%of the coal gangue content,and 25%of the fly ash content.The order of the significance of the influencing factors of the 28 d strength of the filling body sample is fine gangue rate,fly ash content,and coal gangue content.The optimal mix ratio is fine gangue rate 40%,coal gangue content 45%,and fly ash content 40%.③The main hydration products of the filling material are ettringite and C-S-H gel.The lap compactness of the two determines the development of the strength of the filling body sample.With the extension of hydration age,the hydration products continue to develop,overlap with each other to form a dense network structure,refine the structural holes,and significantly improve the mechanical strength of the filling body samples.