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<p>The transition to low-carbon cement alternatives like Limestone Calcined Clay Cement (LC<sup>3</sup>) requires the effective utilization of locally available clay resources through optimized calcination strategies. This study investigates the influence of calcination temperature and duration on the phase development, pozzolanic reactivity, and mechanical performance of high-grade kaolinite (HGK) and two low-grade kaolinite clays (LGK-1 and LGK-2) sourced from India. Thermal activation was performed at 600–900&#xa0;°C for 1–3 hours, and the resulting clays were incorporated into LC<sup>3</sup> mortars. The optimal calcination conditions were identified as 800&#xa0;°C for 2 h for HGK and LGK-1, and 900&#xa0;°C for 2 h for LGK-2, based on compressive strength and strength activity index (SAI). Phase analysis via XRD, TGA and FTIR revealed that optimal calcination resulted in the complete transformation of kaolinite and montmorillonite into reactive amorphous phases, with reduced illite content. LC<sup>3</sup> mortars made with optimally calcined clays showed significantly enhanced early-age strength correlated with increased formation of ettringite, monocarboaluminate, hemicarboaluminate, and calcite, along with substantially reduced portlandite content. Compared to OPC, all LC<sup>3</sup> mixes exhibited higher ettringite and carboaluminate phase content and longer setting times. From the result of strength efficiency per unit emission and strength efficiency per unit energy of LC<sup>3</sup> demonstrates superior eco-efficiency compared to OPC in terms of energy and CO<sub>2</sub> emissions.</p>

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Effect of Calcination Parameters on Phase Development and Mechanical Performance of LC3 Incorporating Low-Grade Clays

  • 期刊论文

  • 发表日期：

    2026年1月6日

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  • Kunal Jee Thakur,
  • Arya Anuj Jee,
  • Arvind Kumar Agnihotri

摘要

The transition to low-carbon cement alternatives like Limestone Calcined Clay Cement (LC3) requires the effective utilization of locally available clay resources through optimized calcination strategies. This study investigates the influence of calcination temperature and duration on the phase development, pozzolanic reactivity, and mechanical performance of high-grade kaolinite (HGK) and two low-grade kaolinite clays (LGK-1 and LGK-2) sourced from India. Thermal activation was performed at 600–900 °C for 1–3 hours, and the resulting clays were incorporated into LC3 mortars. The optimal calcination conditions were identified as 800 °C for 2 h for HGK and LGK-1, and 900 °C for 2 h for LGK-2, based on compressive strength and strength activity index (SAI). Phase analysis via XRD, TGA and FTIR revealed that optimal calcination resulted in the complete transformation of kaolinite and montmorillonite into reactive amorphous phases, with reduced illite content. LC3 mortars made with optimally calcined clays showed significantly enhanced early-age strength correlated with increased formation of ettringite, monocarboaluminate, hemicarboaluminate, and calcite, along with substantially reduced portlandite content. Compared to OPC, all LC3 mixes exhibited higher ettringite and carboaluminate phase content and longer setting times. From the result of strength efficiency per unit emission and strength efficiency per unit energy of LC3 demonstrates superior eco-efficiency compared to OPC in terms of energy and CO2 emissions.