Properties of geopolymer from circulating fluidized bed combustion coal bottom ash

▶ Dry cured geopolymers exhibit a heterogeneous and porous gel matrix. ▶ The Si/Na atomic ratio of the main reaction product (N-A-S-H gel) is close to 1. ▶ Low Si/Na ratio (0.5) correspond to a more crystalline stage of the N-A-S-H gel. ▶ N-A-S-H gel has small pores which facilitate the escape of moisture when it is heated. ▶ N-A-S-H gel became more amorphous, attaining higher Si/Al ratio of 4.54 at 800 °C.