Thermal behaviour of blends kaolin-boehmite and metakaolin-boehmite based-geopolymers: physical and mechanical properties

Thermal stability is an essential parameter to consider before using a binder at elevated temperature. This study investigates the effects of boehmite (B) on thermal behaviour and fired characteristics of sodium-based geopolymers respectively obtained from kaolin (K) and metakaolin (MK). To that end, B was used to partially replace the aluminosilicates (0 and 30 % by mass), the resulting mixtures were alkali-activated to produce geopolymers (GK, GK B 30 , GMK, GMK B 30 ), which were cured, heated (900-1100-1150°C) and characterised. Thermal behaviour revealed that B improves the thermal stability in the products of GK B 30 and GMK B 30 . Additionally, the compressive strengths were improved respectively of about 66.7 and 82.0% in GK B 30 (1100°C) and GMK B 30 (1150°C), attributed to densification coupled with the presence of mullite, corundum and quartz. These products endowed with improved fired characteristics and enhanced thermal stability can be used as binders for refractory applications as well as precursors for the production of ceramics.