TY - JOUR AU - Tawfik, A. AU - Abd El-Raoof, F. AU - Katsuki, H. AU - MacKenzie, K. J.D. AU - Komarneni, S. PY - 2016/06/30 Y2 - 2024/03/29 TI - K-Based Geopolymer from metakaolin: roles of K/Al ratio and water or steam Curing at different temperatures JF - Materiales de Construcción JA - Mater. constr. VL - 66 IS - 322 SE - Research Articles DO - 10.3989/mc.2016.03115 UR - https://materconstrucc.revistas.csic.es/index.php/materconstrucc/article/view/1984 SP - e081 AB - 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 <sup>27</sup>Al and <sup>29</sup>Si 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. ER -