Fly Ash

Fly ash consists of the inorganic matter within coal that has been melted at high temperature during coal combustion, solidified while suspended in the flue gases, and collected by electrostatic precipitators or other devices before the flue gases are released into the atmosphere. Fly ash is the lighter, less dense part of coal ash, consisting of small spherical particles having pozzolanic or some cementitious properties. It is distinguished from the heavier, denser part of coal ash, the bottom ash, which is collected at the bottom of the boilers and consists of coarse nonspherical particles that lack pozzoanic/cementitious properties. Fly ash, also known as pulverized fuel ash (PFA) because of its fine powdery form and pozzolanic and cementitious nature, has many established applications in the production of concrete-related construction and pavement materials.