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<p>Efficient, cost-effective, and eco-friendly cement-free cementitious materials have garnered renewed interest in sustainable shelter construction. This study investigates the cementitious behavior of hydrated blends of lime (up to 30 wt.%) and illitic-kaolinitic clay heated to 900&#xa0;°C. The microstructures of these blends, cured for up to 28&#xa0;days at temperatures of 22, 35, and 60&#xa0;°C, were analyzed using X-ray diffraction, Fourier-transform infrared spectroscopy, thermal analysis, and scanning electron microscopy. Key technical characteristics of the cured blends were also evaluated. The results demonstrated the formation of C<sub>4</sub>AcH<sub>11</sub>, C<sub>4</sub>AH<sub>13</sub> and C-S–H hydrates, along with calcite and vaterite. The Ca/Si (0.25–1) and Ca/Al (0.64–2.56) ratios supported the formation of C–S–H, and other hydrates. Analysis of cured blends with the clay heated fine fraction (particle size &lt; 50&#xa0;µm) revealed the formation of Ca<sub>2</sub>Al(OH)<sub>7</sub>.3H<sub>2</sub>O alongside previously identified hydrates. Despite this, no significant differences in hydrate morphology were detected. The increased formation of hydrates and calcite, driven by higher lime content or extended curing, significantly improved bending and compressive strengths, which peaked at approximately 7, and 25&#xa0;MPa, respectively. In contrast, water absorption was only slightly affected, likely due to the limited impact of the formed phases on open porosity. Based on these findings, the studied pozzolans are deemed suitable as cementitious materials.</p>

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Insights into Phase Transformation and Key Technical Characteristics of Cured Blends of Heated Clay and Lime

  • 期刊论文

  • 发表日期：

    2025年5月16日

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  • Mohamed Hajjaji,
  • Yassmine Mleza,
  • Younoussa Millogo

摘要

Efficient, cost-effective, and eco-friendly cement-free cementitious materials have garnered renewed interest in sustainable shelter construction. This study investigates the cementitious behavior of hydrated blends of lime (up to 30 wt.%) and illitic-kaolinitic clay heated to 900 °C. The microstructures of these blends, cured for up to 28 days at temperatures of 22, 35, and 60 °C, were analyzed using X-ray diffraction, Fourier-transform infrared spectroscopy, thermal analysis, and scanning electron microscopy. Key technical characteristics of the cured blends were also evaluated. The results demonstrated the formation of C4AcH11, C4AH13 and C-S–H hydrates, along with calcite and vaterite. The Ca/Si (0.25–1) and Ca/Al (0.64–2.56) ratios supported the formation of C–S–H, and other hydrates. Analysis of cured blends with the clay heated fine fraction (particle size < 50 µm) revealed the formation of Ca2Al(OH)7.3H2O alongside previously identified hydrates. Despite this, no significant differences in hydrate morphology were detected. The increased formation of hydrates and calcite, driven by higher lime content or extended curing, significantly improved bending and compressive strengths, which peaked at approximately 7, and 25 MPa, respectively. In contrast, water absorption was only slightly affected, likely due to the limited impact of the formed phases on open porosity. Based on these findings, the studied pozzolans are deemed suitable as cementitious materials.