Fluidity and rheological properties with time-dependence of cemented fine-grained coal gangue backfill containing HPMC using response surface method.

Efficient gangue grouting in goafs requires accurate measurement of time-dependent rheological properties of the slurry and slurry fluidity to ensure proper transport. This paper measured the relevant parameters for cemented fine-grained coal gangue backfill containing HPMC, analyzed them by the response surface method, and explained the chemical environment and hydration products in the slurry through Zeta potential and electrical conductivity. Furthermore, the relationships between slump flow (S f), yield stress (τ 0), viscosity coefficient (η), and curing time were studied. It is found that (1) based on the constructed quadratic polynomial regression models of the S f , τ 0 and η , the fluidity of CFGHB decreases with increasing concentration and HPMC and OPC2 contents, (concentration > HPMC content > OPC content). S f is significantly affected by the interaction terms in the order of x 1 x 3 > x 1 x 2 > x 2 x 3 , while τ 0 and η are significantly influenced by x 1 x 2 and x 1 x 3 ; (2) as curing time increases, S f decreases, while τ 0 and η increase. The influence of curing time on η are approximate convex quadratic functions, and τ 0 are approximate concave quadratic functions; (3) the addition of HPMC and OPC enhances the cohesion of the CFGHB matrix through flocculation, increasing the flow resistance of coal gangue particles. The lower concentration facilitates the hydration reaction, adding HPMC negatively impacts it. Concentration has a more significant effect on hydration reactions than HPMC content; (4) the S f of the slurry exhibits a negative correlation with τ 0 and η. CFGHB slurry was fitted with quadratic curves and cubic curves. Additionally, the statistical model of τ 0 and η for CFGHB as a function of curing time describes the continuous flow state of the slurry within 120 minutes, indicating a strong time dependence in the rheological parameters of the slurry. This study provides the optimization of coal gangue grouting and goaf materials and their engineering application. • The fluidity and rheology parameters for cemented fine-grained coal gangue backfill containing HPMC are measured and analyzed. • The slurry's chemical environment and hydration products through Zeta potential and electrical conductivity are analyzed. • The evolution of the fluidity and rheological properties of the slurry with the increase in curing time was revealed. • The mathematical relationships among slump flow, yield stress, viscosity coefficient, and curing time are revealed. [ABSTRACT FROM AUTHOR]