K-based geopolymer from metakaolin: Roles of K/Al ratio and water or steam curing at different temperatures

A. Tawfk, F. Abd El-Raoof, H. Katsuki, K. J.D. Mackenzie, S. Komarneni

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K-based geopolymer binder was prepared by reacting metakaolin with alkaline solutions having different potassium contents and by water curing at room temperature and 80 °C as well as steam curing at 150 and 180 °C. The phase formation, microstructure and Al and Si nearest neighbor environments were studied using XRD, TEM and 27Al and 29Si MAS NMR spectroscopy, respectively. The results revealed that amorphous alumino-silicates were predominant in geopolymer prepared by curing up to 28 days at room temperature or at 80 °C. The amorphous alumino-silicates persisted after hydrothermal treatment at 150 °C/48 hrs and even at 180 °C/30 hrs. However, the samples cured hydrothermally at 180 °C/48 hrs revealed formation of crystalline potassium aluminum silicate and chabazite phases. The Al nearest neighbor environments was not significantly affected by increasing the K/Al ratio up to 1.55 or by the curing temperatures. On the other hand, the geopolymer reaction appears to have increased when cured at 80 °C or steam cured at 150° and 180 °C and crystalline aluminosilicates resulted when the geopolymer sample was hydrothermally treated at 180 °C/48 hrs.

Original languageEnglish (US)
Article numbere081
JournalMateriales de Construccion
Issue number322
StatePublished - Apr 1 2016

All Science Journal Classification (ASJC) codes

  • Building and Construction
  • General Materials Science
  • Mechanics of Materials


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