The exploration of effect for nano-Al2O3 on solid waste based superfine tailings cemented paste backfill: Pyrolysis property, hydration mechanism and environmental risk

• Published in: Construction & building materials 2024-11, Vol.452, p.139035, Article 139035
• Main Authors: Zhang, Bo, Chen, Deping, Han, Bin, Hu, Yafei, Li, Keqing
• Format: Article
• Language: English
• Subjects: Cemented paste backfill; Hydration mechanisms; Leaching risk; Pyrolysis; Superfine tailings
• ISSN: 0950-0618
• DOI: 10.1016/j.conbuildmat.2024.139035

Resource utilization of superfine tailings has become a key research direction in filling mining. This study analyzes the mechanical properties, pyrolysis mechanism and hydration mechanism of nano-Al2O3(NA)-doped solid waste based superfine tailings cemented paste backfill (SWSCPB) by multiple microscopic characterization methods and pyrolysis kinetic theory. The results show that the main temperature interval for the pyrolysis of SWSCPB to happen is 280–900 °C, which is divided into two stages of dehydroxylation and decarbonization. The apparent activation energy(E) and pre-index factor(A) of pyrolysis are higher than those of NA0 and NA2 at 1 % NA dosage, indicating that NA increases the energy barrier of pyrolysis, the percentage of activated molecules, and the collision probability of hydration products in SWSCPB, but decreases due to agglomeration at exceeds 1 % NA dosage. NA can enhance macroscopic strength of SWSCPB, with the highest strength at 1 % NA dosage. Compared with NA0 and NA2, more hydration products such as AFt and C-(A)-S-H are present in NA1, and the distribution of Q2 and Q4 in C-(A)-S-H is more pronounced, with a higher degree of polymerization, a stronger tendency for the conversion of non-bridging to bridging oxygen bonds, and fewer pores in the microstructure of SWSCPB. The NA dosage can provide more nuclei for the formation of AFt, C-(A)-S-H in SWSCPB, and can also promote the replacement of Si by Al for the conversion of C-S-H to C-(A)-S-H with higher polymerization. In addition, the leaching risk and mechanism of heavy metal ions from SWSCPB are preliminarily explored in combination with leaching experiments. The results provide new insights and guidance for the application of SWSCPB in filling mining under cleaner production targets. [Display omitted] •NA dosage changes the pyrolysis mechanism of hydration products in SWSCPB, which can enhance the energy barrier of the pyrolysis reaction.•The optimal dosage of NA is 1 %, which can effectively enhance the thermal stability and microscopic compactness of SWSCPB and promote the formation of SWSCPB strength.•The strength and microstructure of SWSCPB deteriorate due to agglomeration when NA dosage exceeds 1 %.•SWSCPB has no risk of potential heavy metal leaching and complies with mine environmental protection requirements.