Various types of pulverized fuel ashes (IS 4305)

Ash is generated by the burning of ground or pulverized or crushed coal or lignite-fired boilers. It can be fly ash, bottom ash, pond ash, or mound ash. As per IS 4305, it may be of the following types:

Siliceous Pulverized Fuel Ash — Pulverized fuel ash with reactive calcium oxide less than 10 percent, by mass. Such fly ash is normally produced from burning anthracite or bituminous coal and has pozzolanic properties.

Calcareous Pulverized Fuel Ash — Pulverized fuel ash with reactive calcium oxide not less than 10 percent by mass. Such fly ash is normally produced from lignite or sub-bituminous coal and has both pozzolanic and hydraulic properties.

Reactive Calcium Oxide (CaO) — That fraction of the calcium oxide which, under normal hardening conditions, can form calcium silicate hydrates or calcium aluminate hydrates.

Fly Ash — Pulverized fly ash extracted from flue gases by any suitable process such as by cyclone separator or electrostatic precipitator. 

Bottom Ash — Pulverized fuel ash collected from the bottom of boilers by any suitable process. 

Pond Ash — Fly ash or bottom ash or both mixed in any proportion and conveyed in the form of water slurry and deposited in a pond or lagoon. 

Mound Ash — Fly ash or bottom ash or both mixed in any proportion and conveyed or carried in dry form and deposited dry. 

Source: IS 3812:2003