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<p>Emergency geotechnical engineering and post-disaster reconstruction require soil stabilization technologies capable of achieving rapid strength gain with low environmental impact. However, conventional cement-based stabilization of excavated soils and construction and demolition waste (CDW) is constrained by high-carbon emissions, long curing durations, and insufficient early strength. The development of low-carbon binders capable of rapid strength gain therefore remains a critical challenge. In this study, a CDW-based geopolymer composed of ground granulated blast-furnace slag (GGBS), waste glass, and clay red brick powder is proposed for the stabilization of excavated soils. To further accelerate strength development, microwave curing is introduced as a rapid and energy-efficient activation technique. A series of mechanical properties tests and microstructural characterization techniques, including unconfined compressive strength (UCS) testing, X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR), were employed to investigate the effects of alkali activation parameters (NaOH concentration, Na<sub>2</sub>SiO<sub>3</sub> modulus, and alkali-to-solid ratio), precursor composition, and microwave curing conditions on the mechanical performance and strength improvement mechanisms of stabilized soils. The results demonstrate that the UCS of the geopolymer-stabilized soil exhibits a nonlinear relationship with the alkali activation parameters: Strength initially increases and subsequently decreases beyond an optimal threshold for NaOH concentration, Na<sub>2</sub>SiO<sub>3</sub> modulus, and alkali-to-solid ratio. Microwave curing significantly enhances early strength development, achieving more than 50% of the 28 days UCS immediately after treatment. However, excessive microwave power or prolonged curing leads to a strength reduction due to microstructural damage. Microstructural analyses reveal that strength enhancement is associated with the formation of a dense, three-dimensional sodium aluminosilicate hydrate (N–A–S–H) gel network and coexisting calcium silicate hydrate (C–S–H) phases, while strength degradation at higher energy inputs is linked to microcrack development and gel dehydration. Overall, the findings provide experimental evidence and mechanistic insight into the feasibility of microwave-assisted, CDW-derived geopolymer binders for rapid soil stabilization, particularly suited for emergency, temporary, and surface-layer geotechnical engineering applications.</p>

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Mechanical properties and microscopic mechanism of microwave-induced rapidly stabilized soil with CDW-based geopolymer

  • 期刊论文

  • 发表日期：

    2026年5月2日

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  • Xia Bian,
  • Shuyao Zuo,
  • Jianyu Xiao,
  • Lingling Zeng,
  • Xiusong Shi,
  • Jian Ji,
  • Yutao Zhang,
  • Biao Xu

摘要

Emergency geotechnical engineering and post-disaster reconstruction require soil stabilization technologies capable of achieving rapid strength gain with low environmental impact. However, conventional cement-based stabilization of excavated soils and construction and demolition waste (CDW) is constrained by high-carbon emissions, long curing durations, and insufficient early strength. The development of low-carbon binders capable of rapid strength gain therefore remains a critical challenge. In this study, a CDW-based geopolymer composed of ground granulated blast-furnace slag (GGBS), waste glass, and clay red brick powder is proposed for the stabilization of excavated soils. To further accelerate strength development, microwave curing is introduced as a rapid and energy-efficient activation technique. A series of mechanical properties tests and microstructural characterization techniques, including unconfined compressive strength (UCS) testing, X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR), were employed to investigate the effects of alkali activation parameters (NaOH concentration, Na2SiO3 modulus, and alkali-to-solid ratio), precursor composition, and microwave curing conditions on the mechanical performance and strength improvement mechanisms of stabilized soils. The results demonstrate that the UCS of the geopolymer-stabilized soil exhibits a nonlinear relationship with the alkali activation parameters: Strength initially increases and subsequently decreases beyond an optimal threshold for NaOH concentration, Na2SiO3 modulus, and alkali-to-solid ratio. Microwave curing significantly enhances early strength development, achieving more than 50% of the 28 days UCS immediately after treatment. However, excessive microwave power or prolonged curing leads to a strength reduction due to microstructural damage. Microstructural analyses reveal that strength enhancement is associated with the formation of a dense, three-dimensional sodium aluminosilicate hydrate (N–A–S–H) gel network and coexisting calcium silicate hydrate (C–S–H) phases, while strength degradation at higher energy inputs is linked to microcrack development and gel dehydration. Overall, the findings provide experimental evidence and mechanistic insight into the feasibility of microwave-assisted, CDW-derived geopolymer binders for rapid soil stabilization, particularly suited for emergency, temporary, and surface-layer geotechnical engineering applications.