Mechanical properties and microstructure of coal cinder-based ultra-fine tailings cemented tailings body

Cementitious materials are the main binders used in mine filling and play a critical role in determining the mechanical properties of cemented tailings backfill (CTB). But, the materials typically account for over 60% of total filling expenses. The objective of this study is to utilize solid waste cinders as a substitute for certain cement-like materials, aiming to lower the cost of filling while maintaining the strength characteristics of CTB. Through measuring the fluidity and strength characteristics of slurry with different CC replacement levels, and the microstructure analysis of backfill, the study finds that: 1) The addition of CC can improve the fluidity of ultra-fine tailings filling slurry and adding 1 ∼ 2 mm CC can both improve the fluidity of CTB and the compressive strength of CTB. 2) The strength of the filling body can be improved by replacing 20% of the cementitious material with CC when the surface pore size of CC with porous structure is similar to the median particle size of the tailings. 3) The lower packing density of CC and the hydrophilic mineral components on the surface reduced the interfacial tension between solid and liquid, which enhanced the dispersion ability of CC in the slurry. 4) Coal cinders replace part of cement-like materials to reduce filling costs and solid waste emissions.