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Purpose <p>Various materials have been proposed to improve chemical methods for stabilizing marine soft clay. However, there is still a lack of comprehensive understanding of the mechanical performance and micro-mechanisms of alkali-activated binders in marine soft clay treated with solid waste under chloride attack. This study aims to investigate the chloride erosion resistance of alkali-activated Ground Granulated Blast Furnace Slag (GGBS) marine clay stabilized with CaO (0–2%) and MgO (6–7%).</p> Materials and methods <p>The marine clay was treated with various combinations of GGBS, CaO, and MgO at different curing ages. Unconfined compressive strength (UCS) testing was performed to assess the mechanical performance of the alkaline activator formulations under chloride exposure. Microstructural analysis using scanning electron microscopy (SEM) and X-ray diffraction (XRD) revealed the key mechanisms of chloride resistance in the stabilized clays.</p> Results and discussion <p>Alkali-activated GGBS marine clay exhibits superior chloride resistance compared to ordinary Portland cement. The presence of Cl⁻ significantly alters hydration mechanisms. While adequate CaO (≥ 1%) enhances strength, lower CaO (&lt; 1%) leads to the decomposition of Friedel’s salt, increasing porosity and causing strength loss, evidenced by a 22.5% decrease in UCS over 28 days for low-CaO mixes. In contrast, higher MgO content (≥ 7%) markedly improves performance by forming hydrotalcite, which strengthens the matrix and increases UCS. Specifically, 7% MgO resulted in a 66.5&#xa0;kPa strength gain at 28 days compared to 6% MgO under the same curing age. Microstructural analysis confirms that Friedel’s salt forms under Cl⁻ exposure in alkali-activated marine soft clay, coating calcium silicate hydrate (C-S-H) gels, which later dissolve in lower pH conditions, releasing water, creating pores, and compromising long-term strength.</p> Conclusions <p>The findings recommend formulations with low CaO and high MgO for optimal durability. This research offers both theoretical and practical insights for effective marine clay stabilization through the utilization of industrial by-products.</p>

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Insights into chloride-induced calcium-magnesium hydrates formation in alkali-activated marine soft clay

  • 期刊论文

  • 发表日期：

    2026年6月26日

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  • Quanyi Zhang,
  • Zhengjian Liu,
  • Junjun Ni,
  • Qiang Guo,
  • Yuchen Wang

摘要

Purpose

Various materials have been proposed to improve chemical methods for stabilizing marine soft clay. However, there is still a lack of comprehensive understanding of the mechanical performance and micro-mechanisms of alkali-activated binders in marine soft clay treated with solid waste under chloride attack. This study aims to investigate the chloride erosion resistance of alkali-activated Ground Granulated Blast Furnace Slag (GGBS) marine clay stabilized with CaO (0–2%) and MgO (6–7%).

Materials and methods

The marine clay was treated with various combinations of GGBS, CaO, and MgO at different curing ages. Unconfined compressive strength (UCS) testing was performed to assess the mechanical performance of the alkaline activator formulations under chloride exposure. Microstructural analysis using scanning electron microscopy (SEM) and X-ray diffraction (XRD) revealed the key mechanisms of chloride resistance in the stabilized clays.

Results and discussion

Alkali-activated GGBS marine clay exhibits superior chloride resistance compared to ordinary Portland cement. The presence of Cl⁻ significantly alters hydration mechanisms. While adequate CaO (≥ 1%) enhances strength, lower CaO (< 1%) leads to the decomposition of Friedel’s salt, increasing porosity and causing strength loss, evidenced by a 22.5% decrease in UCS over 28 days for low-CaO mixes. In contrast, higher MgO content (≥ 7%) markedly improves performance by forming hydrotalcite, which strengthens the matrix and increases UCS. Specifically, 7% MgO resulted in a 66.5 kPa strength gain at 28 days compared to 6% MgO under the same curing age. Microstructural analysis confirms that Friedel’s salt forms under Cl⁻ exposure in alkali-activated marine soft clay, coating calcium silicate hydrate (C-S-H) gels, which later dissolve in lower pH conditions, releasing water, creating pores, and compromising long-term strength.

Conclusions

The findings recommend formulations with low CaO and high MgO for optimal durability. This research offers both theoretical and practical insights for effective marine clay stabilization through the utilization of industrial by-products.