Thermal behavior and characteristics of fired geopolymers produced from local Cameroonian metakaolin

• Published in: Ceramics international 2014-04, Vol.40 (3), p.4515-4520
• Main Authors: Elimbi, A., Tchakoute, H.K., Kondoh, M., Dika Manga, J.
• Format: Article
• Language: English
• Subjects: Amorphous phase; Ceramics; Characteristics; Crystal structure; Dilatometry; Geopolymers; Hydration; Metakaolin; Microstructure; Phases; Shrinkage; Thermal behavior; Transformations
• ISSN: 0272-8842; 1873-3956
• DOI: 10.1016/j.ceramint.2013.08.126

The thermal behavior along with certain characteristics of geopolymers produced from local Cameroonian metakaolin and heated up to 1000°C were examined. Geopolymers fired up to 900°C had the same physical aspect as initial ones and those fired at 1000°C warped, were glazed and blistered. The TG showed elimination of water according to two stages. The dilatometric curves of preheated samples showed shrinkage between 90 and 250°C followed by expansion and sintering. The samples heated up to 700°C were amorphous and new crystalline phases appeared around 900°C. The microstructure of geopolymers heated between 300 and 900°C showed progressive disruption and the linear shrinkage increased. The water absorption of the samples fired up to 700°C increased slightly and tremendously around 900°C. A drastic decrease of compressive strength was observed with the samples fired between 300 and 900°C. Hence, the characteristics of geopolymers lessened with elimination of the water which forms hydration spheres around the compensating cations (Na+) opposed to tetrahedral groups AlO4− along with transformation of amorphous phase.