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<p>Traditional cement-based materials’ economic and environmental concerns urge low-carbon alternatives. This study activates coal gangue via hydrothermal synthesis − low temperature calcination to explore optimal activation conditions for cement substitution. A Box-Behnken response surface experiment was designed with 28d compressive strength as the response index to study the effects of hydrothermal temperature, Ca/Si ratio, NaOH concentration, and calcination temperature on coal gangue-based cementitious materials. Single-factor optimization was conducted based on significant factors identified via response surface analysis. Phase evolution and hydration mechanisms were analyzed using XRD, SEM, TG-DSC, etc. Results indicated that optimal conditions were 90&#xa0;°C, Ca/Si = 2.0, NaOH = 1.5%, and 800&#xa0;°C, with the Ca/Si ratio and calcination temperature exerting the most significant impact, achieving a 28d compressive strength of 20.1&#xa0;MPa. At Ca/Si = 2.0, the highest content of C<sub>12</sub>A<sub>7</sub> was found in the clinker. The formation of β-C<sub>2</sub>S and α’<sub>H</sub>-C<sub>2</sub>S at 800&#xa0;°C facilitated the densification of C–S–H with ettringite. Hydrothermal pre-treatment lowered the C<sub>2</sub>S synthesis temperature by 200&#xa0;°C and enhanced the 28d compressive strength to 191% of that obtained using the one-step calcination method. The results provide theoretical support for the utilization of coal gangue as a cementitious material, promoting its sustainable resource utilization.</p>

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Preparation of new coal gangue-based cementitious material via hydrothermal synthesis–low temperature calcination method

  • 期刊论文

  • 发表日期：

    2025年8月30日

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  • Tingye Qi,
  • Lubin Li,
  • Junjie He,
  • Guorui Feng,
  • Linfei Wang,
  • Hongtao Xu,
  • Tian Qiu,
  • Siyuan Cheng,
  • Xinkai Qi,
  • Kexin Xu

摘要

Traditional cement-based materials’ economic and environmental concerns urge low-carbon alternatives. This study activates coal gangue via hydrothermal synthesis − low temperature calcination to explore optimal activation conditions for cement substitution. A Box-Behnken response surface experiment was designed with 28d compressive strength as the response index to study the effects of hydrothermal temperature, Ca/Si ratio, NaOH concentration, and calcination temperature on coal gangue-based cementitious materials. Single-factor optimization was conducted based on significant factors identified via response surface analysis. Phase evolution and hydration mechanisms were analyzed using XRD, SEM, TG-DSC, etc. Results indicated that optimal conditions were 90 °C, Ca/Si = 2.0, NaOH = 1.5%, and 800 °C, with the Ca/Si ratio and calcination temperature exerting the most significant impact, achieving a 28d compressive strength of 20.1 MPa. At Ca/Si = 2.0, the highest content of C12A7 was found in the clinker. The formation of β-C2S and α’H-C2S at 800 °C facilitated the densification of C–S–H with ettringite. Hydrothermal pre-treatment lowered the C2S synthesis temperature by 200 °C and enhanced the 28d compressive strength to 191% of that obtained using the one-step calcination method. The results provide theoretical support for the utilization of coal gangue as a cementitious material, promoting its sustainable resource utilization.