Page 223 - AJWEP-22-5

Rheological properties of coal gangue slurry

A B

Figure 3. Thermogravimetry‑differential scanning calorimetry analysis: (A) Coal gangue and (B) fly ash
Abbreviations: DSC: Differential scanning calorimetry analysis; TG: Thermogravimetry.

Table 2. Factors and levels used in the orthogonal and comparatively analyzed. To meet the operational
experimental design requirements of the viscometer, 220 mL of slurry was
Level Factor A: Factor B: Factor C: Fly prepared in a beaker, and viscosity tests were performed
Solid volume Coal gangue ash‑to‑coal by adding superplasticizer dosages of 0.01, 0.03, 0.05,
concentration particle size gangue mass 0.1, 0.15, 0.2, 0.25, and 0.3 wt%.
(%) (mesh) ratio
1 50 50 7:3 2.5. Water bleeding rate of mixed slurries under
2 60 100 6:4 injection pressure
3 70 150 5:5 The slurry was prepared with a solid concentration of
4 - - 4:6 70%. Coal gangue particles of three sizes—50, 100, and
150 mesh—were selected. The fly ash-to-coal gangue
5 - - 3:7 mass ratio was controlled at 7:3, 6:4, 5:5, 4:6, and 3:7.
Water bleeding tests were conducted under applied
(25 ± 2°C) was gradually added while mixing at 300 ± pressures of 0.1, 0.2, 0.3, and 0.4 MPa. The experiments
50 rpm using a digital overhead stirrer equipped with examined the effects of coal gangue particle size,
a four-blade propeller (diameter: 50 mm) (Mixing material ratio, and pressure on the water bleeding rate
continued for 5 ± 0.5 min after complete water addition of the slurry.
to ensure homogeneity ). The slurry was immediately The slurry was manually stirred with a glass rod
transferred to a 100 mL graduated cylinder maintained at directly in the pressure vessel. Approximately 200 mL
25 ± 2°C for density measurement and subsequent tests. of slurry was prepared for each ratio, and pressure
For viscometry, 360 mL slurry samples were prepared was applied to the vessel immediately after mixing.
under identical mixing conditions and tested within A stopwatch was used to record the bleeding volume.
2 min of preparation using a temperature-controlled Due to the rapid bleeding observed during the 1 min,
st
(25 ± 0.5°C) rotational viscometer. measurements were taken every 5–10 s. After the 1 min,
st
bleeding slowed, and measurements were recorded at
2.4. Reducing viscosity by superplasticizers 1-min intervals until no further bleeding occurred. The
A slurry with a solid volume concentration of 60% was total bleeding volume was recorded to calculate the
prepared and placed in 100 mL graduated cylinders for final water bleeding rate of the slurry.
water bleeding experiments. Subsequently, 0.1 wt% of
superplasticizer was added to each of these two slurries 3. Results and discussion
to conduct water bleeding tests. A mixture with a fly
ash-to-coal gangue mass ratio of 3:7 and a solid volume 3.1. Effect of composition on rheological properties
concentration of 60% was selected as the representative 3.1.1. Influence on slurry density
sample to analyze the effect of superplasticizers In this study, the three selected factors were assumed
on viscosity. Two types of superplasticizers – to have no interaction effects. A mixed-level
polycarboxylate and sulfamic acid – were selected L18 (3 × 5 ) orthogonal array was adopted, involving
1
2

Volume 22 Issue 5 (2025) 217 doi: 10.36922/AJWEP025210162