Abstract
Geopolymers are made by adding aluminosilicates to concentrated alkali solutions for dissolution and subsequent polymerisation to take place. They are amorphous to semi-crystalline three dimensional aluminosilicate networks. They have been studied for many years as a possible improvement on cement in respect of compressive strength, resistance to fire, heat and acidity, and as a medium for the encapsulation of hazardous or low/ intermediate radioactive waste. In this work we investigated the microstructure by scanning and transmission electron microscopy and compressive strength of geopolymers made by using New Zealand flyash. X-ray diffraction showed them to be amorphous with a small amount of crystalline phases such as calcite and quartz. Amorphous phases were confirmed by transmission electron microscopy. Compressive strength testing of pastes and mortars was carried out after 1, 7 and 28 days of curing. Their strength is discussed with respect to microstructural features with curing.
