Abstract: The mixture of metakaolin and calcite or gypsum instead of circulating fluidized bed (CFB) fly ash was used to investigate the influence of SiO2/Al2O3 and Na2O/Al2O3 on the setting time and compressive strength of geopolymer.The results of X-ray diffraction (XRD) and Raman spectrum proved that there are 10 chemical reactions occurred in the preparation of metakaolin-based geopolymer.The experimental results also showed that: the variation of sodium components in alkali activator controlled the amount of complex silicon or aluminum anion group, and the formation of CSH and (Na, Ca)-PSS depended on the amount of complex silicon anion group.In the SiO2-Al2O3-CaO-Na2O system, the formation of hydrogarnet showed negative effect on the strength development of geopolymer when Na2O/Al2O3≥1.1, and the geopolymer product set too fast to mix properly when SiO2/Al2O3≥3.0.

Key words: alkali activator;metakaolin;circulating fluidized bed;geopolymer