Thermal investigation of fine alumina powder reinforced Na-metakaolin-based geopolymer binder for refractory applications

Abstract

Geopolymers have become an alternative binder material for high-temperature applications. The thermal properties of geopolymer products are significantly influenced by the fillers used in their production. In this study, fine α-alumina powders 50% of which are smaller than 6.45 μm (D(0.5) = 6.45 μm) in the ratio of 100 wt.% were added as fillers to relatively high water included (H2O/Al2O3 = 19.6) Na-metakaolin-based geopolymer resin. Although there was a high amount of fine powders included, a composite binder which could be placed in form smoothly by wet casting method was obtained thanks to sufficient water in the resin. The thermal behaviour of the cured composites was examined from room temperature (RT) to 1250 °C. In the conclusion of the study, it was noted that the samples had significant dimensional stability up to 1000 °C with the increasing compressive strength. Investigations showed that the deformation expected to occur with the viscous sintering in the geopolymer matrix between 750 and 1000 °C shifted to higher temperatures due to the refractory effect of the high amount of fine filler. This characteristic revealed that this type of composite binder has a potential to be used alone to produce fine alumina-geopolymer refractory composites or used as a binder for coarser refractory aggregates to produce various refractories.