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<p>To address the issues of high-carbon emissions, high cost, and insufficient long-term stability associated with traditional cement-based solidification materials, this study developed a low-carbon, low-cost alkali-activated solidifying agent entirely from industrial solid wastes (RAS). The agent was prepared using ground granulated blast-furnace slag (GGBS), fly ash (FA), calcium carbide residue (CCR), and desulfurization ash (DA) for the solidification/stabilization (S/S) treatment of cadmium (Cd<sup>2+</sup>)-contaminated soil. A systematic investigation was conducted involving macroperformance tests such as unconfined compressive strength (UCS), toxicity characteristic leaching procedure (TCLP), pH value, and electrical resistivity under varying conditions of binder content (0%, 10%, 15%, 20%), initial Cd<sup>2+</sup> concentration (0, 900, 2000, 4000&#xa0;mg/kg), and curing age (7, 14, 28&#xa0;days). This was combined with microanalytical techniques including X-ray diffraction (XRD) and scanning electron microscopy (SEM) to elucidate the strength development, Cd<sup>2+</sup> immobilization efficiency, and underlying mechanisms. The results show that RAS significantly enhances the mechanical properties of the contaminated soil, with the UCS increasing by up to 16 times, meeting the strength requirements for fill materials. The Cd<sup>2+</sup> leaching concentration decreased by 95–99.2%, and even heavily contaminated soil (4000&#xa0;mg/kg) achieved safe standards after 28&#xa0;days of curing. A strong linear correlation was observed between electrical resistivity and UCS, suggesting its potential for rapid, non-destructive assessment of S/S effectiveness. Microstructural analysis confirmed that Cd<sup>2+</sup> is immobilized through multiple mechanisms, including precipitation as Cd(OH)<sub>2</sub>, adsorption by C–S–H gels, isomorphic substitution, and physical encapsulation. This study provides technical support and a theoretical foundation for the green and efficient remediation of cadmium-contaminated soil.</p>

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Solidification/stabilization performance and mechanisms of Cd-contaminated soil using alkali-activated binder based entirely on solid wastes

  • 期刊论文

  • 发表日期：

    2026年7月3日

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  • Jie Xu,
  • Jingdong Jiang,
  • Xinru Xu,
  • Jia He,
  • Yufeng Gao

摘要

To address the issues of high-carbon emissions, high cost, and insufficient long-term stability associated with traditional cement-based solidification materials, this study developed a low-carbon, low-cost alkali-activated solidifying agent entirely from industrial solid wastes (RAS). The agent was prepared using ground granulated blast-furnace slag (GGBS), fly ash (FA), calcium carbide residue (CCR), and desulfurization ash (DA) for the solidification/stabilization (S/S) treatment of cadmium (Cd2+)-contaminated soil. A systematic investigation was conducted involving macroperformance tests such as unconfined compressive strength (UCS), toxicity characteristic leaching procedure (TCLP), pH value, and electrical resistivity under varying conditions of binder content (0%, 10%, 15%, 20%), initial Cd2+ concentration (0, 900, 2000, 4000 mg/kg), and curing age (7, 14, 28 days). This was combined with microanalytical techniques including X-ray diffraction (XRD) and scanning electron microscopy (SEM) to elucidate the strength development, Cd2+ immobilization efficiency, and underlying mechanisms. The results show that RAS significantly enhances the mechanical properties of the contaminated soil, with the UCS increasing by up to 16 times, meeting the strength requirements for fill materials. The Cd2+ leaching concentration decreased by 95–99.2%, and even heavily contaminated soil (4000 mg/kg) achieved safe standards after 28 days of curing. A strong linear correlation was observed between electrical resistivity and UCS, suggesting its potential for rapid, non-destructive assessment of S/S effectiveness. Microstructural analysis confirmed that Cd2+ is immobilized through multiple mechanisms, including precipitation as Cd(OH)2, adsorption by C–S–H gels, isomorphic substitution, and physical encapsulation. This study provides technical support and a theoretical foundation for the green and efficient remediation of cadmium-contaminated soil.