Page 185 - AJWEP-22-5

Asian Journal of Water, Environment and Pollution. Vol. 22, No. 5 (2025), pp. 179-192.
doi: 10.36922/AJWEP025200154

ORIGINAL RESEARCH ARTICLE

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

Jianjun Hou , Zhigang Li , Jian Wang , Zhiling Ren , Yang Yang ,
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Zhongquan Liu , and Linqiang Mao *
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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
*Corresponding author: Linqiang Mao (maolq@cczu.edu.cn)
Received: May 14, 2025; Revised: July 8, 2025; Accepted: July 11, 2025; Published online: July 31, 2025

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 i = 0.91 effectively
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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

1. Introduction discharged from coal-fired power plants, is rich in
silicon dioxide (SiO ) and aluminum oxide (Al O ) and
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Coal gangue and fly ash are two major solid wastes is commonly used in cement, concrete, and foundation
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generated during coal mining and combustion. Coal treatments. However, the massive amounts produced
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gangue, a by-product of coal seam extraction, is annually have rendered conventional disposal methods
primarily composed of clay minerals, quartz, and increasingly insufficient to meet the growing storage
pyrite. Its long-term accumulation not only occupies demands. Consequently, developing efficient and
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land resources but also poses environmental hazards, environmentally friendly utilization strategies for
such as spontaneous combustion and acid mine coal gangue and fly ash is of great significance for
drainage. Fly ash, a fine particulate solid waste sustainable waste management.
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Volume 22 Issue 5 (2025) 179 doi: 10.36922/AJWEP025200154