Backfilling and grouting in the goaf are effective methods that can efficiently dispose of solid wastes including coal gangue (CG) and coal gasification slag (CGS). When backfilling is solely for solid waste disposal, the strength requirement for backfill materials is low. In view of this, a gangue and coal gasification slag-based backfill material (GCBM) was prepared, using a low content of alkali-activated slag (AAS) to adjust its mechanical properties. Considering three influencing factors (solid content, CGS content, and AAS content), single-factor experiments and optimization experiments based on response surface methodology (RSM) were conducted, with fluidity and strength as the optimization objectives. Finally, the hardening mechanism and microstructure of GCBM were analyzed. Test results show that the fluidity of GCBM is negatively correlated with solid content, CGS content, and AAS content; the strength is positively correlated with solid content (in a certain range) and AAS content, and first increases and then decreases with the increment of CGS content. The optimal mix-proportions obtained via RSM were as follows: 75.35wt% solid content, 24.13wt% CGS content, and 4.94wt% AAS content. Analysis of GCBM’s chemical composition and microstructure indicates that its main gel phases are calcium aluminosilic-ate hydrate (C–A–S–H), sodium aluminosilicate hydrate (N–A–S–H), and potassium aluminosilicate hydrate (K–A–S–H). The gels begin to adhere to and wrap inert solid particles when elements Si, Al, Ca, Na, and K dissolved in the alkali-activated system undergo heterogeneous nucleation on solid particle surfaces. The presence of multiple spherical pits on the fracture planes suggests that glass microspheres in CGS to some extent reduce GCBM’s strength. The specific surface area and pore structure of GCBM were analyzed, and its environmental safety was preliminarily verified. The results provide theoretical guidance for the large-scale, efficient backfilling disposal of solid wastes, especially CG and CGS.
| [1] |
G.W. Zhao, T. Wu, G.Z. Ren, et al., Reusing waste coal gangue to improve the dispersivity and mechanical properties of dispersive soil, J. Cleaner Prod., 404(2023), art. No. 136993.
|
| [2] |
S.Y. Yan, W.W. Xuan, C.Y. Cao, and J.S. Zhang, A review of sustainable utilization and prospect of coal gasification slag, Environ. Res., 238(2023), art. No. 117186.
|
| [3] |
S.R. Xie, H. Pan, W.Z. Gu, et al., Technology and engineering test of filling goaf with coal gangue slurry, Sci. Rep., 13(2023), No. 1, art. No. 20536.
|
| [4] |
J.Q. Wang, J.X. Zhang, M. Li, M. Sartaj, and Y.B. Wang, A numerical simulation of the interaction of aggregate and rockfill in a gangue fluidized filling method, Sustainability, 14(2022), No. 19, art. No. 12838.
|
| [5] |
L. Li, Q.X. Huang, X. Zuo, et al., Study on the slurry diffusion law of fluidized filling gangue in the caving goaf of thick coal seam fully mechanized caving mining, Energies, 15(2022), No. 21, art. No. 8164.
|
| [6] |
L.Z. Guo, M. Zhou, X.Y. Wang, C. Li, and H.Q. Jia, Preparation of coal gangue-slag-fly ash geopolymer grouting materials, Constr. Build. Mater., 328(2022), art. No. 126997.
|
| [7] |
Koshy N, Dondrob K, Hu LM, Wen QB, Meegoda JN. Synthesis and characterization of geopolymers derived from coal gangue, fly ash and red mud. Constr. Build. Mater., 2019, 206287
|
| [8] |
J.Y. Wu, S. Yang, M. Williamson, et al., Microscopic mechanism of cellulose nanofibers modified cemented gangue backfill materials, Adv. Compos. Hybrid Mater., 8(2025), No. 2, art. No. 177.
|
| [9] |
Yang YB, Lai XP, Zhang Y, et al. . Strength deterioration and energy dissipation characteristics of cemented backfill with different gangue particle size distributions. J. Mater. Res. Technol., 2023, 255122
|
| [10] |
P. Yang, L. Liu, Y.L. Suo, et al., Investigating the synergistic effects of magnesia-coal slag based solid waste cementitious materials and its basic characteristics as a backfill material, Sci. Total Environ., 880(2023), art. No. 163209.
|
| [11] |
Yu KP, Ma LQ, Huo BB, Ngo I, Wu YH, Zhai JT. Study on the fluidity and mechanical properties of multi-source coal-based solid waste (MCSW) filling material. J. Mater. Res. Technol., 2024, 282924
|
| [12] |
Q. Guo, B.B. Huo, K.P. Yu, Y.L. Xiong, and B.L. Li, Using acetic acid as a preconditioner to optimize rheology of alkali-activated coal gasification slag based backfill pastes, Miner. Eng., 218(2024), art. No. 109040.
|
| [13] |
P. Yang, Y.L. Suo, L. Liu, et al., Study on the curing mechanism of cemented backfill materials prepared from sodium sulfate modified coal gasification slag, J. Build. Eng., 62(2022), art. No. 105318.
|
| [14] |
C.D. Min, Y. Shi, X.Y. Lu, Z.X. Liu, and Y.N. Zhou, Cemented backfill using Ca(OH)2-pretreated phosphogypsum as aggregate: Hydration characteristics, structural features and strength development, Constr. Build. Mater., 402(2023), art. No. 133011.
|
| [15] |
Y.H. Zhao, X.H. Zhou, Q.S. Zhou, H.Y. Zhu, F.J. Cheng, and H.D. Chen, Optimization design of anhydrous phosphogypsum-based backfill materials incorporating carbide slag and blast furnace slag by response surface method, Miner. Eng., 215(2024), art. No. 108820.
|
| [16] |
Wei XD, Chen TL, Shen GK, Ding F. Alkali-activated slag backfill grout materials optimization: Statistical RSM modelling and NSGA-II performance control. J. Mater. Res. Technol., 2023, 245613
|
| [17] |
X.G. Wang, Y. Yu, F.B. Zou, et al., High performance C–A–S–H seeds from fly ash-carbide slag for activating lithium slag towards a low carbon binder, J. Environ. Manage., 345(2023), art. No. 118658.
|
| [18] |
Li YL, Guo SJ, Yang RS, Xie LY, Lu SH. Effects of gangue particle-size gradation on damage and failure behavior of cemented backfill under uniaxial compression. Int. J. Miner. Metall. Mater., 2025, 3271483
|
| [19] |
Yin Q, Wen F, Tao ZG, et al. . Effects of aggregate size distribution and carbon nanotubes on the mechanical properties of cemented gangue backfill samples under true triaxial compression. Int. J. Miner. Metall. Mater., 2025, 322311
|
| [20] |
Xu G, Shi XM. Characteristics and applications of fly ash as a sustainable construction material: A state-of-the-art review. Resour. Conserv. Recycl., 2018, 13695
|
| [21] |
S.D. Lin, X.G. Jiang, Y.M. Zhao, and J.H. Yan, Zeolite greenly synthesized from fly ash and its resource utilization: A review, Sci. Total Environ., 851(2022), art. No. 158182.
|
| [22] |
Y. Wang, L. Burris, R.D. Hooton, C.R. Shearer, and P. Suraneni, Effects of unconventional fly ashes on cementitious paste properties, Cem. Concr. Compos., 125(2022), art. No. 104291.
|
| [23] |
J.W. Feng, Z.Y. Zhang, W.M. Guan, et al., Review of the backfill materials in Chinese underground coal mining, Minerals, 13(2023), No. 4, art. No. 473.
|
| [24] |
W.C. Feng, M. Li, J.X. Zhang, H.D. Wang, S. Liu, and W.L. Wang, Load-bearing deformation and strength evolution of a filling body prepared by compacting a gangue waste-slurry mixture, J. Cleaner Prod., 493(2025), art. No. 144990.
|
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