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<p>Geopolymer has attracted an increasing interest as sustainable binder for road-base construction, however, single-alkali activation often makes it difficult to simultaneously achieve high mechanical performance and workable setting-time window. This study develops a ternary composite alkali-activated geopolymer using Na₂CO₃/KOH/Na₂SiO₃ as activator to solidify a multi-solid-waste blend of furnace slag, fly ash, and steel slag. Response surface methodology was first employed to optimize chemical baseline, obtaining an optimal silicate modulus of 1.4 and a total alkali dosage of 7.2%. Under this fixed baseline, the Na₂CO₃/KOH molar ratio was systematically varied to quantify its effects on compressive strength, flexural strength, and setting time, and the microstructural evolution was examined by environmental scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray diffraction. TCAG achieved a maximum 28-day compressive strength of 52.31&#xa0;MPa at 50% KOH replacement ratio, whereas the largest flexural strength of 6.30&#xa0;MPa occurs at 40% KOH replacement, indicating different optimization requirements for compressive and flexural performance. Increasing Na₂CO₃ content effectively prolonged setting time, providing a controllable setting-time window, but excessive Na₂CO₃ led to a lower strength. Spectroscopic and microstructural results suggested that the molar ratio of Na₂CO₃ to KOH alters gel chemistry and matrix densification, which is consistent with test results of strength and setting time. These findings offer a practical approach for designing high-strength geopolymer with controllable setting behavior, supporting their potential applications as sustainable road-base binder.</p>

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All-Solid-Waste Based Geopolymer Activated by Ternary Composite Alkali: Preparation, Properties, Strengthening and Toughening Mechanisms

  • 期刊论文

  • 发表日期：

    2026年4月22日

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  • Yidong Kang,
  • Fengxun Yuan,
  • Wenjing Xia,
  • Tao Xu

摘要

Geopolymer has attracted an increasing interest as sustainable binder for road-base construction, however, single-alkali activation often makes it difficult to simultaneously achieve high mechanical performance and workable setting-time window. This study develops a ternary composite alkali-activated geopolymer using Na₂CO₃/KOH/Na₂SiO₃ as activator to solidify a multi-solid-waste blend of furnace slag, fly ash, and steel slag. Response surface methodology was first employed to optimize chemical baseline, obtaining an optimal silicate modulus of 1.4 and a total alkali dosage of 7.2%. Under this fixed baseline, the Na₂CO₃/KOH molar ratio was systematically varied to quantify its effects on compressive strength, flexural strength, and setting time, and the microstructural evolution was examined by environmental scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray diffraction. TCAG achieved a maximum 28-day compressive strength of 52.31 MPa at 50% KOH replacement ratio, whereas the largest flexural strength of 6.30 MPa occurs at 40% KOH replacement, indicating different optimization requirements for compressive and flexural performance. Increasing Na₂CO₃ content effectively prolonged setting time, providing a controllable setting-time window, but excessive Na₂CO₃ led to a lower strength. Spectroscopic and microstructural results suggested that the molar ratio of Na₂CO₃ to KOH alters gel chemistry and matrix densification, which is consistent with test results of strength and setting time. These findings offer a practical approach for designing high-strength geopolymer with controllable setting behavior, supporting their potential applications as sustainable road-base binder.