The effect of composition and temperature on the properties of fly ash- and kaolinite-based geopolymers

Fundamental research into the geopolymerisation process is increasing rapidly because of the potential commercial application of this technology. Despite this, however, very little work has been undertaken to determine the relationship between composition and temperature on the final chemical and physical properties of geopolymeric products derived from waste materials. The present study shows that the differences in reactivity of source materials, used during the synthesis of waste-based geopolymers, significantly affect the final properties of the geopolymeric material. It is proposed that these observed changes in material properties are due to the incomplete dissolution of the waste material. The water content, the fly ash/kaolinite ratio, as well as the type of metal silicate used have a substantial effect on the final properties of the geopolymer. In particular, the current work shows that the thermal history of the source materials, such as kaolinite, as well as the curing regime for the geopolymer are important factors that must be taken into consideration when designing a geopolymer product for a specific application.