Coal Combustion Products
Coal combustion products (CCPs) can play an important role in concrete production. CCPs are the by-products generated from burning coal in coal-fired power plants. These by-products include:
- fly ash
- bottom ash
- boiler slag
- flue gas desulphurisation gypsum
- others types of material such as fluidised bed combustion ash, cenospheres, and scrubber residues
Fly ash can be used to replace or supplement cement in concrete. In the USA, for example, more than half of the concrete produced is blended with fly ash.
Among the most significant environmental benefits of using fly ash over conventional cement is that greenhouse gas (GHG) emissions can be significantly reduced. For every tonne of fly ash used for a tonne of portland cement (the most common type of cement in general use around the world) approximately one tonne of carbon dioxide is prevented from entering the earth’s atmosphere. Fly ash does not require the energy-intensive kilning process required by portland cement.
Using CCPs reduces GHG emissions, reduces the need for landfill space, and eliminates the need to use primary raw materials. Fly ash produces a concrete that is strong and durable, with resistance to corrosion, alkali-aggregate expansion, sulphate and other forms of chemical attack.
Coal combustion products are expected to continue to play a major role in the concrete market. Their use in other building products is also expected to grow as sustainable construction becomes more prominent, and more architects and building owners understand the benefits of using CCPs.