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<p>Acid mine drainage (AMD) is a widespread environmental concern due to its detrimental impact on groundwater quality. This study evaluated the unconfined compressive strength (<i>q</i><sub>u</sub>), hydraulic conductivity and microstructural evolution of NaOH–MgO-activated GGBS–FA vertical cutoff wall specimens for in situ mixed vertical cutoff walls intended to contain AMD-contaminated groundwater. A set of microstructural analyses were conducted which included X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) with energy-dispersive spectroscopy (EDS) and mercury intrusion porosimetry (MIP). Results showed that <i>q</i><sub>u</sub> increased and hydraulic conductivity to AMD (<i>k</i><sub>c</sub>) and to tap water (<i>k</i><sub>w</sub>) decreased with rising Ca/Si and declining Al/Si ratios, consistent with increasing GGBS–FA ratio. At 28&#xa0;days of curing, GGBS-rich specimens (G6F4, G8F2 and G10F0) achieved <i>q</i><sub>u</sub> values of 1587–2371&#xa0;kPa and <i>k</i><sub>c</sub> values of 4.95 × 10<sup>−11</sup> to 1.89 × 10<sup>−10</sup> m/s, while<i> q</i><sub>u</sub> and <i>k</i><sub>c</sub> of FA-rich specimens (G2F8 and G4F6) ranged from 770 to 1300&#xa0;kPa and from 7.77 × 10<sup>−10</sup> to 1.18 × 10<sup>−9</sup> m/s, respectively. Although AMD exposure slightly increased <i>k</i><sub>c</sub>, all specimens maintained <i>k</i><sub>c</sub>/<i>k</i><sub>w</sub> ratios between 2.0 and 5.0, demonstrating acceptable hydraulic performance. XRD and FTIR analyses revealed a transition from N–A–S–H to C–A–S–H gels with increasing GGBS content, meanwhile ettringite (Aft) formation in G10F0 and G8F2 and hydrotalcite (Ht) presence in FA-rich specimens. The FTIR Si–O–T band upshifted from 999 to 1086&#xa0;cm<sup>−1</sup> as FA content decreased from 80 to 0%, which correlated linearly with both increasing <i>q</i><sub>u</sub> and decreasing log<i>k</i><sub>c</sub>, indicating progressive gel polymerization and matrix densification. MIP confirmed reduced total porosity with higher GGBS–FA ratios. Furthermore, a positive linear correlation was obtained between log<i>k</i><sub>c</sub> and <i>V</i><sub>large-inter</sub> /<i>V</i><sub>total</sub>. These findings underscore the potential of GGBS–FA geopolymers as durable, impermeable materials for vertical cutoff walls in containing AMD-contaminated groundwater.</p>

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GGBS-fly ash geopolymer for in situ mixed vertical cutoff walls in containing acid mine drainage leachate-contaminated groundwater: unconfined compressive strength, hydraulic conductivity and microstructure

  • 期刊论文

  • 发表日期：

    2025年11月3日

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  • Heng Zhuang,
  • Cheng-Zhu Kou,
  • Xian-Lei Fu,
  • Zhe-Yuan Jiang,
  • Min Wang,
  • Chen-Yang Yu,
  • Yan-Jun Du

摘要

Acid mine drainage (AMD) is a widespread environmental concern due to its detrimental impact on groundwater quality. This study evaluated the unconfined compressive strength (qu), hydraulic conductivity and microstructural evolution of NaOH–MgO-activated GGBS–FA vertical cutoff wall specimens for in situ mixed vertical cutoff walls intended to contain AMD-contaminated groundwater. A set of microstructural analyses were conducted which included X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) with energy-dispersive spectroscopy (EDS) and mercury intrusion porosimetry (MIP). Results showed that qu increased and hydraulic conductivity to AMD (kc) and to tap water (kw) decreased with rising Ca/Si and declining Al/Si ratios, consistent with increasing GGBS–FA ratio. At 28 days of curing, GGBS-rich specimens (G6F4, G8F2 and G10F0) achieved qu values of 1587–2371 kPa and kc values of 4.95 × 10−11 to 1.89 × 10−10 m/s, while qu and kc of FA-rich specimens (G2F8 and G4F6) ranged from 770 to 1300 kPa and from 7.77 × 10−10 to 1.18 × 10−9 m/s, respectively. Although AMD exposure slightly increased kc, all specimens maintained kc/kw ratios between 2.0 and 5.0, demonstrating acceptable hydraulic performance. XRD and FTIR analyses revealed a transition from N–A–S–H to C–A–S–H gels with increasing GGBS content, meanwhile ettringite (Aft) formation in G10F0 and G8F2 and hydrotalcite (Ht) presence in FA-rich specimens. The FTIR Si–O–T band upshifted from 999 to 1086 cm−1 as FA content decreased from 80 to 0%, which correlated linearly with both increasing qu and decreasing logkc, indicating progressive gel polymerization and matrix densification. MIP confirmed reduced total porosity with higher GGBS–FA ratios. Furthermore, a positive linear correlation was obtained between logkc and Vlarge-inter /Vtotal. These findings underscore the potential of GGBS–FA geopolymers as durable, impermeable materials for vertical cutoff walls in containing AMD-contaminated groundwater.