Page 189 - AJWEP-22-5

Use of coal gangue for mine backfill

was free of moisture. Using an electronic balance (ZSX Primus III+, Rigaku, Japan). The particle size
(Shanghai Jingyi Co., Ltd, China), the masses of the distributions of coal gangue were analyzed using a laser
coarse aggregates from the top, middle, and bottom particle size analyzer (LS I3320, Beckman Coulter,
sections of the mold were recorded as m , m , and m , USA). Mineralogical compositions were characterized
3
1
2
respectively. The SI was using Equation III. using an X-ray powder diffractometer (X-ray diffraction
m m [XRD], Smartlab 9, Japan) at a scanning rate of
SI 3 1 100% (III) 5°/min over a 2θ range of 5° to 90°. The XRD data
m
4 were processed and phase-identified using the MDI
Where SI represents the segregation index (%), m₁ Jade 6 software (Materials Data, USA). Rheological
and m are the mass of coarse aggregates at the top and parameters, including yield stress and plastic viscosity,
3
bottom of the mold, and m is the average mass of the were analyzed and plotted using Origin 2021 (OriginLab
4
coarse aggregates. Corporation, USA).
All slurry preparation and testing were conducted
2.3.5. Plastic viscosity and yield stress under controlled laboratory conditions with ambient
Plastic viscosity is a key parameter for assessing the flow temperatures maintained between 20°C and 25°C
resistance of slurries, with lower viscosity indicating and relative humidity around 50 – 60%. These stable
better flowability. Yield stress also plays a critical role environmental parameters ensured consistent hydration
in slurry flowability and stability. According to the and rheological measurements, minimizing variability
Technical Specifications for Tailings Paste Backfill in the results.
(GB/T 39489 – 2020), the yield stress should be below
200 Pa to ensure pumpability and uniform distribution. 3. Results and discussion
In this study, plastic viscosity and yield stress were
measured using a rotational viscometer (NXS-11B, Compared with conventional cement-based backfill
Shanghai Kence Co., Ltd, China). As the rotor spins, materials, the coal gangue-fly ash slurry offers
shear stress is uniformly distributed along the cylindrical significant cost and environmental advantages. Cement
interface, allowing the calculation of shear force using binders typically incur higher production costs and
Equation IV. generate substantial carbon emissions during clinker
manufacture, whereas coal gangue and fly ash are
2R 2 1 (IV) industrial by-products, reducing raw material expenses
R 2 R 2
1 2 and promoting waste valorization. Reusing these
Where γ is the shear force, R is the radius of the outer wastes minimizes environmental pollution and landfill
1
cylinder (mm), R is the radius of the inner cylinder demand, aligning with sustainable-mining practices and
2
(mm), and ω is the shear velocity (s ). providing a greener alternative to traditional backfill
-1
materials.
2.3.6. Compressive strength
The compressive strength of slurry specimens cured for 3.1. Feasibility analysis of producing slurry coal
7, 14, and 28 days was tested using a universal testing gangue and fly ash
machine (Wuxi Jianyi Co., Ltd, China) at a loading rate Figure 2 presents the XRD patterns of two raw materials:
of 0.5 mm/min. The maximum load-bearing capacity Coal gangue and fly ash. Coal gangue (Figure 2A) is
of each specimen was recorded, and the compressive primarily composed of quartz, pyrite, anatase, albite,
strength was calculated using Equation V. sillimanite, and muscovite. The mineral composition is
F dominated by silicate minerals, with small amounts of
max (V) iron-titanium minerals (pyrite and anatase), indicating
c
A both volcanic ash activity and potential alkaline mineral
Where σ is the compressive strength (MPa), F max is release. Fly ash (Figure 2B) is mainly composed of
c
the maximum load at failure (N), and A is the cross- quartz, hematite (Fe O ), and amorphous aluminosilicate
2
3
sectional area of the specimen (mm ). glass. The presence of gypsum (CaSO ) suggests its
2
4
potential involvement in sulfate-activation reactions.
2.4. Analytical methods Chemical analysis (Table 1) shows that both
The chemical compositions of coal gangue and fly materials are rich in SiO , Al O , and Fe O , though
3
2
2
3
2
ash were determined using an XRF spectrometer their forms differ significantly: Si and Al in coal gangue
Volume 22 Issue 5 (2025) 183 doi: 10.36922/AJWEP025200154