Characterizations of FBC/PCC fly ash geopolymeric composites

Fluidized bed combustion (FBC) is a well-established coal burning process for small factories owing to energy efficiency and low environmental impact. Due to the low burning temperatures at 800–900 °C, FBC fly ash is not suitable for use as pozzolan in concrete mixture and requires proper improvement before utilization. This research proposed the use of FBC fly ash as a source material for geopolymeric composite. Grinding was applied to improve the physical property of FBC fly ash. In addition, the ground FBC fly ash was blended with pulverized coal combustion (PCC) high calcium fly ash to increase its glassy phase. The geopolymeric composites were then prepared using the blended powder mixed with alkali solutions, and thermally-cured to promote the reaction. The hardened specimens were subjected to chemical and physical tests. Resistance to acid and salt attacks of PCC/FBC fly ash composites was also investigated. Results showed the changes in chemical compositions and physical performances of geopolymeric materials. PCC fly ash helped enhance the properties of FBC fly ash based composite and the dense and homogeneous matrix was achieved. Additional CSH was formed resulting in the increase in strength of composites as a function of time. However, the durability was affected with the use of the high calcium PCC fly ash due to the presence of calcium and the associated hydration products.