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Rheological properties of coal gangue slurry

A B

C

Figure 6. Influence of three factors on the estimated marginal mean of water bleeding rate: (A) Solid volume
concentration, (B) coal gangue particle size, and (C) fly ash‑to‑coal gangue mass ratio

Table 6. Significance analysis of influencing solid volume concentration (60–70%) reduced bleeding
factors on the water bleeding rate of slurry by 20–40% (Figure 6A). However, unlike cemented

Factor Sum of DOF Average F‑value p‑value tailings, fly ash—coal gangue slurries achieved stability
squared variance without cement, thereby reducing costs.
deviations This study suggests that replacing 40–70% of fly ash
A 0.021 2 0.011 35.290 0.000 with coal gangue (mass ratio 6:4 to 3:7) can directly
B 0.011 4 0.015 13.566 0.001 reduce raw material costs. Fly ash is priced at 20–50$ per
C 0.014 6 0.002 15.644 0.000 ton in China, whereas coal gangue is a zero-cost industrial
byproduct that only requires grinding. For a typical
Deviation 0.003 8 backfilling operation utilizing 100,000 tons of solids per
Sum 1.105 18 year, substituting 50% of fly ash with coal gangue could
Abbreviation: DOF: Degrees of freedom. result in annual savings of 0.75–2.25$ million. In addition,
incorporating coal gangue at 40–70% mass ratio diverts
indicating that higher coal gangue content in slurry 40,000–70,000 tons of waste per year from landfills for
reduced water separation. Notably, when the mass ratio every 100,000 tons of backfill, thereby avoiding landfill
ranged from 7:3 to 4:6, the water bleeding rate declined disposal fees of 5–15$/ton and generating additional
gradually. However, when the fly ash-to-coal gangue savings of $0.2–1.05 million annually. Moreover, this
mass ratio shifted from 4:6 to 3:7, the water bleeding approach mitigates long-term environmental liabilities
rate declined significantly. This suggests that the associated with coal gangue stockpiles.
variations in water bleeding at different stages were due
to changes in particle packing density and interstitial 3.2. Effect of superplasticizer on rheological
water retention mechanisms at higher coal gangue properties
proportions. 28,29 These findings align with the previous In practical engineering applications, slurry is typically
study by Du et al., which demonstrated that a higher transported through pipelines into grouting layers. 24,30
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Volume 22 Issue 5 (2025) 221 doi: 10.36922/AJWEP025210162