AccScience Publishing / AJWEP / Online First / DOI: 10.36922/AJWEP025200154
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ORIGINAL RESEARCH ARTICLE

Utilization of coal gangue and fly ash for sustainable mine backfill: Rheology and stability optimization of slurry

Jianjun Hou1,2 ,  Zhigang Li1 ,  Jian Wang2 ,  Zhiling Ren2 ,  Yang Yang2 ,  Zhongquan Liu1 ,  Linqiang Mao1*
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1 Department of Mining Engineering, Team 113 of Coalfield Geology Bureau of Guizhou Province, Guiyang, Guizhou, China
2 Department of Environment Engineering, School of Environment Science and Technology, Changzhou University, Changzhou, Jiangsu, China
AJWEP, 025200154 https://doi.org/10.36922/AJWEP025200154
Received: 14 May 2025 | Revised: 8 July 2025 | Accepted: 11 July 2025 | Published online: 31 July 2025
© 2025 by the Author(s). This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution 4.0 International License ( https://creativecommons.org/licenses/by/4.0/ )
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Abstract

By systematically optimizing particle size distribution and solid mass concentration, this study develops high-performance coal gangue-fly ash backfill slurry with enhanced rheological properties and stability. X-ray diffraction and performance analyses confirmed that the synergistic combination of crystalline aluminosilicates in coal gangue and amorphous aluminosilicate glass in fly ash significantly contributes to the formation of a cohesive C-(A)-S-H gel network under alkaline conditions, thereby improving the mechanical integrity and stability of the backfill matrix. Slurries with solid mass concentrations between 68% and 76% displayed typical Bingham plastic behavior, with increasing concentration significantly improving both plastic viscosity and yield stress, thus enhancing resistance to bleeding and segregation. Particle size analysis indicated that a distribution modulus of ik = 0.91 effectively minimized bleeding while maintaining high flowability, improving slurry homogeneity and pumpability. An optimal formulation was identified at a 72% solid mass concentration with optimized particle size distribution, providing a balance between workability and stability. These results confirm the potential of coal gangue-fly ash systems as sustainable and cost-effective backfill materials and offer practical guidance for mix design in large-scale underground mining applications. Furthermore, this approach promotes the green reuse of bulk industrial by-products, advancing the sustainable development of solid waste while supporting safe and environmentally responsible mine reclamation.

Keywords
Backfilling slurry
Coal gangue
Fly ash
Flowability
Stability
Funding
This research was funded by the Guizhou Provincial Energy Bureau Science and Technology Project (Project name: Technical Research and Development of Coal Gangue Underground Backfill Mining Technology and Its Pilot Application by Guizhou Zhaping Coal Industry Co., Ltd; Grant number: 2023–68).
Conflict of interest
The authors declare no competing interests.
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Asian Journal of Water, Environment and Pollution, Electronic ISSN: 1875-8568 Print ISSN: 0972-9860, Published by AccScience Publishing
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