Fly ash properties, characterization, and applications: A review

Fly ash (FA) is the principal industrial waste byproduct from the burning of solid fuels. FA is a powdery solid that is constituted mostly of unburned carbon (UC), metal oxides (Si, Fe, Ca, and Al), and other inorganic substances. UC is an inexpensive source of activated carbon that plays an important role in FA adsorption capacity. Due to the broad variability in its composition, FA characterization is challenging. Accordingly, FA is categorized into class F, and class C according to the maximum and minimum % of SiO2, Al2O3, Fe2O3, and SO3. X-ray diffraction, and fluorescence, and scanning microscopy with an energy dispersive spectroscopy are the common techniques employed to characterize FA. FA was used to remove hazardous contaminants, organic and inorganic chemicals, and dyes from wastewater. Furthermore, investigations revealed that FA has promising potential beneficial usage in the construction industry, particularly in cement and concrete production. FA has been added to cement in a reduced nanosize form giving good durability and minimizing concrete pores size to resist adverse environment. In this article, significant properties, characterization methods and, applications of FA were summarized. (C) 2021 The Author(s). Published by Elsevier B.V. on behalf of King Saud University.