PREPARATION AND PROPERTIES OF FLY ASH-BASED GEOPOLYMER FOAMS

• Published in: Ceramics (Praha) Vol. 58; no. 3; pp. 188 - 197
• Main Authors: Skvara, F, Sulc, R, Tisler, Z, Skricik, P, Smilauer, V, Zlamalova, Cilova Z
• Format: Journal Article
• Language: English
• Published: University of Chemistry and Technology, Prague 01.01.2014
• Subjects: Aluminosilicates; Aluminum; Aluminum silicates; Cracks; Firing; Fly ash; Foam; Foams; Geopolymer; Macro-porosity; Pore formation; Silicon carbide
• ISSN: 0862-5468; 1804-5847

An extremely porous geopolymer material, a non-combustible alumino-silicate foam, can be prepared by incorporating pore-forming agents into mixtures consisting of an alkaline activating agent (NaOH + water glass) and fly ash. Aluminium powder or Si-containing materials (silica fume, FeSi or SiC) may be used as pore-forming agents. Pore formation occurs immediately after Al powder addition, but collapse must be prevented by incorporating Portland cement or lime. Si reaction in the alkaline environment is boosted by the presence of an alumino-silicate material, i.e. fly ash. The prepared geopolymer foams have similar pore sizes, and a weight similar to that of other inorganic foams. The mechanical properties remained stable for a year. The foams are non-combustible and resist temperatures up to 1000 C without any decomposition. Their shape does not change after exposure to temperatures in the 400-800 C range. In contrast to lime-silicate foams and cement-based foams, firing is not accompanied by crack formation or rehydration.