Thermal phenomena of alkali-activated metakaolin studied with a negative temperature coefficient system

The properties of alkali-activated materials (AAMs) depend on both the type of raw material used and their production procedure. This article presents an inexpensive and easily accessible method, based on using thermistors with a negative temperature coefficient, to analyse phenomena during the geopolymerisation process of AAMs. The described method enables prediction of the final physical and mechanical properties of tested materials and allows unambiguous determination of the quality of raw metakaolin materials in terms of their suitability for geopolymerisation processes and AAM production. This statement was proved by comparing AAMs formed based on metakaolin from three different sources. This article also describes the results of the mineralogical analysis, density, particle size distribution and morphology of the three metakaolins. In addition, the compression strength and FT-Raman spectroscopy of the AAM produced are described. Even though all materials were referred to as metakaolin, the results of this study showed that calcined materials can significantly differentiate the geopolymerisation process and final physical and mechanical properties of AAM.