Discover Civil Engineering (Dec 2024)

Influence of CaO/Al2O3 molar ratio of synthetic calcium aluminate hydrates on the engineering properties of metakaolin-based alkali-activated materials

  • Aimard Manfred Njawa Moudio,
  • Ismailla Hamed Riyap,
  • Jean Mermoz Siewé,
  • Hervé Kouamo Tchakouté,
  • Charles Péguy Nanseu-Njiki,
  • Claus Henning Rüscher,
  • Pengkun Hou

DOI
https://doi.org/10.1007/s44290-024-00147-y
Journal volume & issue
Vol. 1, no. 1
pp. 1 – 17

Abstract

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Abstract This study evaluates the influence of the CaO/Al2O3 molar ratio of synthetic calcium aluminate hydrates on the properties of alkali-activated materials based on metakaolin. Calcium aluminate hydrates with CaO/Al2O3 molar ratios of 0.4, 0.6, 0.8, 1.0 and 1.2 were synthesised from bauxite and eggshells. Alkali-activated materials were prepared in which metakaolin was replaced by 0 and 10 wt.% calcium hydroxide and calcium aluminate hydrate with different CaO/Al2O3 molar ratios. Rice husk ash with a SiO2/Na2O molar ratio of 1.6 was used for the preparation of the hardener. The 28-day compressive strengths of alkali-activated materials containing 0 and 10 wt.% calcium aluminate hydrate with different CaO/Al2O3 molar ratios of 0, 0.4, 0.6, 0.8, 1.0 and 1.2 are 48.86, 63.59, 47.36, 47.89, 34.66 and 32.76 MPa, respectively. 22.08 MPa for that containing 10% by weight of calcium hydroxide. The apparent densities are 1.87, 1.79, 1.99 and 2.10 g/cm3, respectively. It has been found that the best molar ratio of CaO to Al2O3 in the structure of the 10% by weight of calcium aluminate hydrate used to replace metakaolin, which is required to produce alkali-activated materials with higher mechanical and physical properties, is about 0.4. Highlights Calcium aluminate hydrates (CAHs) with molar ratio CaO/Al2O3 of 0.4, 0.6, 0.8, 1.0 and 1.2 were prepared using calcined bauxite, calcined eggshell and distillated water. Calcium hydroxide (CH) was prepared using calcined eggshell and distillated water. Metakaolin was substituted by 0 and 10 wt.% of CH and the different CAHs. The highest strength was archived at 63.59 MPa for alkali-activated material using CAH with molar ratio CaO/Al2O3 of 0.4 as additive.

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