Assessing the suitability of three Australian fly ashes as an aluminosilicate source for geopolymers in high temperature applications

► Morphology and location of crystalline phases affect the degree of reaction of geopolymers. ► Fine fly ash particle size is preferential to synthesise high strength geopolymers. ► High iron content in fly ash reduces post firing mechanical strength. ► Sintering during high temperature exposure can increase strength by up to 5-fold.