Effect of hydration products composition on high temperature resistance of geopolymers

Geopolymer exhibits better high temperature resistance than Portland cement, which makes it an excellent alternative cementitious component for fireproof building materials. It was known that the zeolite-like phase in the hydration products of geopolymers was more stable than the gel phase when subjected to high temperatures. Therefore, adjusting the hydration products composition was expected to further enhance high temperature resistance of geopolymers and broaden its application prospects in the field of fireproof materials. Therein, effect of hydration products composition on the high temperature resistance of geopolymers was evaluated and the composition was adjusted by the alkali fusion activation method. The results showed that hydration products composition played the key role on its high temperature resistance and the promoted formation of the more zeolite-like phase enhanced high temperature resistance of geopolymers. Furthermore, alkali fusion activation was facilitated the transformation of hydration products composition from the gel phase to the zeolite-like phase. Zeolite-like phase content increased significantly and reached up to 78% after the alkali fusion activation method was applied. Moreover, mass loss of sample at 1000°C was only 1.9%, which indicated excellent high temperature resistance. In addition, the zeolite-like phases in hrdration products composition changed with increasing of activation temperature and alkali content. Notably, sodalite, the main hydration product pretreated at 400°C, was transformed into nepheline, which became the dominant zeolite-like phase when pretreated at 600°C. This study provided a feasible method for the transformation of geopolymers composition and a new way to improve high-temperature resistantance of geopolymers.