Synthesis, Stability and Microstructure of a One-Step Mixed Geopolymer Backfill Paste Derived from Diverse Waste Slags

Xianhui Zhao, Haoyu Wang (), Han Gao, Luhui Liang and Jing Yang
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Xianhui Zhao: School of Civil Engineering, Hebei University of Engineering, Handan 056038, China
Haoyu Wang: School of Civil Engineering, Tianjin Renai College, Tianjin 301636, China
Han Gao: School of Mechanical Engineering, Tianjin Renai College, Tianjin 301636, China
Luhui Liang: School of Civil Engineering, Hebei University of Engineering, Handan 056038, China
Jing Yang: School of Civil Engineering, Hebei University of Engineering, Handan 056038, China

Sustainability, 2023, vol. 15, issue 8, 1-28

Abstract: The advent of industrialization has produced an enormous amount of industrial waste slag, which drastically pollutes environmental resources. This study examines the production, stability, and microstructure of a novel backfill geopolymer paste derived from multiple industrial waste slags, including silica-alumina precursors (low-calcium composition) and waste slags (high-calcium composition), as well as two additives. The characteristics of self-hardening were discovered. The effects of low-calcium fly ash, granulated blast furnace slag, red mud, and lime powder on fluidity and compressive strength were then evaluated. To assess the stability, the resistances to drying shrinkage, permeability, and chemical attack by an optimized geopolymer backfill paste were investigated. Furthermore, SEM-EDS, XRD, FTIR, and TG-DSC tests were employed to reveal the microstructures, products, and thermal stability. The results show that the backfill paste hardens well and has no impact on alkalinity dissolution for adjacent soils and water. The optimum sample, P1, had a water-binder ratio of 0.70, resulting in 201 mm fluidity and 2.1 MPa 28-d compressive strength. In terms of drying shrinkage, permeability, and Na 2 SO 4 and NaCl solution attack, sample P1 outperformed the conventional Ordinary Portland cement paste (OPC) for 90 days. The paste P1 containing about 46.0 wt% waste slags meets the fresh and hardened property requirements for goaf backfill, and the chemical binding of P1 is acquired from the mixture of (N,C)-A-S-H, C-S-H, and C-A-S-H gel products. These findings lay the groundwork for the scientific application of a wide range of waste slags in backfill engineering.

Keywords: backfill materials; waste slags; geopolymer; mixing proportion; stability; compressive strength; microstructures (search for similar items in EconPapers)
JEL-codes: O13 Q Q0 Q2 Q3 Q5 Q56 (search for similar items in EconPapers)
Date: 2023
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