Effects of carbonization on gangue–cemented paste backfill properties

ABSTRACT

This study was conducted on the impact of carbonization reaction on the performance of gangue–cemented paste backfill(GCPB). Tests were conducted using a carbonization box with CO₂ concentrations of 0%,5%,and 10%. Each test was conducted for 3,7, and 28 days. We then conducted uniaxial compressive strength(UCS)testing, as well as X-ray diffraction(XRD)and scanning electron microscopy(SEM)analyses to explore the effects of the carbonization reaction on the mechanical properties of the GCPBs under the varying carbonization concentrations. The test results showed that before 28 days, the UCS of the GCPB increased with time. The higher the CO₂ concentration, the larger the contact area with the gel material;and the longer time, the slower the growth. Hydration products, such as needle-shaped ettringite(AFt)and white fibrous calcium-silicate-hydrate(C–S–H)gel, carbonize with CO₂ in the air, mainly generating CaCO₃,and combine with incompletely carbonized hydration products to act on the GCPB, increasing the UCS in its growth state. Moreover,we established a CO₂ diffusion and mass transfer equation, indicating a negative correlation between the UCS of the GCPB and the CO₂ concentration,which verified the macroscopic test results. Controlling the CO₂ concentration provides the theoretical and experimental basis for the impact of the carbonization reaction on the performance of GCPBs.

KEYWORDS:

• Gangue–cemented paste backfills
• carbonization
• macroscopic strength
• microstructure
• influence mechanism

Changes list

1. P1, L8-29: I revised the grammar of this part with the help of a professional language translation agency, emphasized the research purpose of the manuscript, and gave the main results of the manuscript.

2. P2, L4-24: I revised the grammar of this part with the help of a professional language translation agency. Moreover, revised the structure of this part to make it more general, and quoted the following works: Alp et al., 2009; Jiang et al., 2020; Koohestani et al., 2018; Kou et al., 2020; Xue et al., 2019a, 2019b; Cui et al. 2020; Luo et al. 2020a, 2020b.

3. P2, L25-26: I revised the grammar of this part with the help of a professional language translation agency.

4. P2, L32-46: Replaced the corresponding Chinese references.

5. P2, L47-50: I revised the grammar of this part with the help of a professional language translation agency.

6. P2, L52-53: Revised the format of references.

7. P2, L54-56: I revised the grammar of this part with the help of a professional language translation agency.

8. P3, L13-26: I revised the grammar of this part with the help of a professional language translation agency.

9. P3, L30-43: I revised the grammar of this part with the help of a professional language translation agency, and provided the originality and core objectives of the present work. Moreover, changed the structure of this part to make it more general.

10. P3, L47-56: I have provided the grain size distribution of coal gangue, cement and fly ash.

11. P4, L3-5: I revised the grammar of this part with the help of a professional language translation agency, and changed Figure 2 to Figure 4.

12. P4, L16-17: I revised the grammar of this part with the help of a professional language translation agency, and Figures 1, 2 have been redrawn.

13. P4, L36-46: I revised the grammar of this part with the help of a professional language translation agency, and changed Figure 3 to Figure 6.

14. P5, L18-56: I revised the grammar of this part with the help of a professional language translation agency, and provided the working conditions of each test.

15. P6, L5-40: I have merged 3.1 and 3.2 under one single subtitle.

16. P6, L3-7: I revised the grammar of this part with the help of a professional language translation agency, and changed Figure 4 to Figure 7.

17. P6, L33-43: I revised the grammar of this part with the help of a professional language translation agency, and changed Figure 5 to Figure 8.

18. P7, L21-31: I revised the grammar of this part with the help of a professional language translation agency, revised the format of references, and replaced the corresponding Chinese references.

19. P7, L37-40: I revised the grammar of this part with the help of a professional language translation agency.

20. P7, L50-51: I revised the grammar of this part with the help of a professional language translation agency, and revised the format of references.

21. P8, L3-5: I revised the grammar of this part with the help of a professional language translation agency, and changed Figure 6 to Figure 9.

22. P8, L28-55: I revised the grammar of this part with the help of a professional language translation agency, changed 3.3 to 3.2, and changed Figure 7 to Figure 10.

23. P9, L3-15: I revised the grammar of this part with the help of a professional language translation agency, revised the format of references, changed Figure 7f to Figure 10f, and changed Figure 7i to Figure 10i.

24. P9, L17: Revised the corresponding Chinese references.

25. P9, L25: Revised the format of references.

26. P9, L30-42: I revised the grammar of this part with the help of a professional language translation agency.

27. P9, L47-52: I revised the grammar of this part with the help of a professional language translation agency.

28. P10, L3-54: I revised the grammar of this part with the help of a professional language translation agency, changed 3.4 to 3.3, and changed Figure 8 to Figure 11.

29. P11, L3-9: I revised the grammar of this part with the help of a professional language translation agency.

30. P11, L16-19: I revised the grammar of this part with the help of a professional language translation agency.

31. P11, L29-37: I revised the grammar of this part with the help of a professional language translation agency.

32. P11, L40: I revised the grammar of this part with the help of a professional language translation agency.

33. P11, L47-56: I revised the grammar of this part with the help of a professional language translation agency, and changed Figure 8 to Figure 11.

34. P12, L3-19: I revised the grammar of this part with the help of a professional language translation agency.

35. P12, L25: Changed Figure 9 to Figure 12.

36. P12, L41: Changed Figure 9 to Figure 12.

37. P12, L48-52: I revised the grammar of this part with the help of a professional language translation agency, that is, deleted part of the content.

38. P13, L9-10: I revised the grammar of this part with the help of a professional language translation agency.

39. P13, L15: I revised the grammar of this part with the help of a professional language translation agency.

40. P13, L21: I revised the grammar of this part with the help of a professional language translation agency.

41. P13, L32: I revised the grammar of this part with the help of a professional language translation agency.

42. P13, L45-52: I revised the grammar of this part with the help of a professional language translation agency.

43. P14, L3-6: I revised the grammar of this part with the help of a professional language translation agency, that is, deleted part of the content.

44. P14, L12-17: I revised the grammar of this part with the help of a professional language translation agency, that is, deleted part of the content.

45. P14, L22: I revised the grammar of this part with the help of a professional language translation agency, that is, deleted part of the content.

46. P14, L30: I revised the grammar of this part with the help of a professional language translation agency, that is, deleted part of the content.

47. P14, L37-40: I revised the grammar of this part with the help of a professional language translation agency.

48. P14, L46-50: I revised the grammar of this part with the help of a professional language translation agency.

49. P15, L8-9: I revised the grammar of this part with the help of a professional language translation agency.

50. P15, L21: I revised the grammar of this part with the help of a professional language translation agency.

51. P15, L34-40: I revised the grammar of this part with the help of a professional language translation agency.

52. P15, L45-51: I revised the grammar of this part with the help of a professional language translation agency, and changed Figure 10(a) to Figure 13(a).

53. P16, L5-53: I revised the grammar of this part with the help of a professional language translation agency. Moreover, I have made a brief summary of this section, highlighted the main findings of the research, and gave some practical filling suggestions. In addition, I have offered some new research paths at the end of this section. In addition, changed Figure 10(b) to Figure 13(b), changed Figure 10 to Figure 13, and revised the format of references.

54. P17, L3-40: I revised the grammar and structure of this part with the help of a professional language translation agency to make this part more compact.

55. P17, L43-46: Due to the fund in the article has been completed, the fund number is changed to 2018TDJH102.

56. P17, L47: Modified the format of the entire references and replaced some Chinese references of this part.

Additional information

Funding

This research was funded by the SDUST Research Fund (grant 2018TDJH102), and funder name is Weitao Liu.