Fly Ash (FA)

Fly Ash produced in Australian power stations are light to mid-grey in colour and tend to resemble the appearance of cement powder. They exhibit a range of values in their physical and chemical properties. These are determined by the interaction of a variety of factors, principally the coal type, coal source, minerals and primary elements present in the coal, furnace type, plant age and the specific combustion conditions experienced by the coal.

The particles in FA are irregular to spherical in shape, with sizes ranging from less than 1 µm to 300 µm. In Australia, the majority of CCPs are produced from burning bituminous and anthracite coal which is categorised as Class F — being mainly SiO2 and AlO2 (<70% ), FeO and <10% CaO with no free lime. Class F ash is highly pozzolanic and reacts with various cementitious materials.

Current and potential uses of FA include:

  • Cement and concrete products
  • Structural fills and embankments
  • Flowable fill
  • Waste stabilisation
  • Agriculture and horticulture — soil amendment, fertiliser, zeolites
  • Manufactured products.