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Liu, et al.

Prolonged pipeline transportation can inevitably cause The zeta potentials of fly ash—coal gangue slurry
blockages, thereby hindering grouting operations. containing either sulfamic acid or polycarboxylate
Therefore, higher slurry fluidity is advantageous for the at mass fractions of 0–0.3 wt% were measured,
injection process, and the water bleeding rate serves as as illustrated in Figure 8. Upon increasing the
an indicator of slurry stability. A slower precipitation superplasticizer concentration to 0.01%, the surface
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rate and lower water bleeding rate are desirable, as they potential of coal gangue increased from −14.9 mV to
enhance the long-term stability of the ground surface −12.04 mV, and further to −10.50 mV. This behavior
post-injection. 31 is attributed to the adsorption of hydrophilic groups
This study investigated viscosity reduction by in polycarboxylate onto the surface of coal gangue,
introducing various dosages of superplasticizer into the forming stable hydration films through interactions
slurries to determine the optimal dosage. Both slurries with water molecules. These films concurrently reduce
were placed in 100 mL graduated cylinders, thoroughly the surface potentials of both raw materials, enhance
stirred with a glass rod, and subjected to water bleeding particle wettability, diminish interparticle spacing
rate tests. Subsequently, 0.1 wt% of superplasticizer– by weakening electrostatic repulsion, and thin the
either polycarboxylate or sulfamic acid—was hydration film around particles–collectively increasing
added to each slurry. Based on experimental results, the free water content and improving slurry fluidity. 33,34
polycarboxylate superplasticizer was identified as a more Although higher superplasticizer concentrations
effective additive for significantly reducing viscosity (>0.1%) exhibited limited efficacy in further reducing
compared to sulfamic acid. As a lipid-based, carbon- zeta potential, their extended polymer chains sterically
storing compound, polycarboxylate superplasticizer also stabilized the system by uniformly dispersing particles
exerts minimal environmental impact. 32 within the slurry matrix. This enhances colloidal
As shown in Figure 7, the viscosity of both stability through combined electrostatic and steric
slurries generally decreased with increasing dosages mechanisms. 15,21 These hydration films simultaneously
of polycarboxylate superplasticizer and gradually reduce the surface potential of both raw materials
reached a plateau. When the dosage reached 0.3 wt%, (Figure 8), enhance particle wettability, and provide
the viscosity remained stable. Notably, the viscosity steric repulsion via extended polymer chains. 15
of the fly ash–coal gangue slurry initially increased Sulfamic acid is widely used to control water
slightly but subsequently decreased and plateaued as bleeding in cementitious systems due to its low
the dosage continued to increase. This phenomenon cost, high dosage tolerance, and compatibility with
is attributed to the chain-like molecular structure of cement matrices. However, its application is often
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polycarboxylate, which effectively disperses fly ash and limited by poor compatibility with supplementary
coal gangue particles within the slurry, thereby reducing cementitious materials–such as fly ash or steel slag—
interparticle interactions. 27,28 These results confirm that which may result in bleeding or segregation due to
polycarboxylate superplasticizer significantly reduces inconsistent particle—fluid interactions. In contrast,
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the viscosity of fly ash—coal gangue slurry. polycarboxylate superplasticizer—a lipid-based,

A B

Figure 7. Influence of sulfamic acid and polycarboxylate superplasticizer on: (A) slurry viscosity and
(B) water bleeding rate

Volume 22 Issue 5 (2025) 222 doi: 10.36922/AJWEP025210162