Bloating of fly ash-based lightweight aggregates

Tóm tắt

The present work characterized two types of fly ash, one from pulverized coal combustion and the other from fluidized bed combustion. The effects of fly ash origins, raw mix proportions, and sintering temperatures on the bloating of lightweight aggregates were studied. The raw mixtures were calculated based on Riley's SiO2 – Al2O3 – fluxing composition diagram. The exothermic combustion reaction of a large amount of unburnt coal causes overheating, which results in boiling and abnormal bloating behavior. Besides, raw mixture compositions outside Riley's composition margin perform efficient bloating with most pore sizes from 0.5 to 1 mm. Hence, besides the fluxing content, one should consider the amount of unburnt coal in the fly ash in synthesizing lightweight aggregates.