Fly ash tweaks concrete for high performance
Our hard coal fly ash is very much in demand among our customers from the construction materials industry. Fly ash can be put to many different uses.
Fly ash can bring its strengths fully to bear above all in the production of concrete and cement. In the concrete, the fine round particles of fly ash act like small ball bearings, improving the water demand. The concrete is easier to work and, in the case of shotcrete and high performance concrete, can be better compacted. The strength of the concrete is also significantly improved because the fly ash particles fill out the cavities in the concrete. Furthermore, the pozzolanic reactivity, i.e. the continued reaction of the fly ash with the calcium hydroxide from the cement and water in the concrete, has a positive long-term effect on the strength and resistance of the concrete.
Due to this ongoing reaction, which usually continues for years, the concrete becomes increasingly more compact, stable and durable. This makes it more resistant, for example against the effects of acid or sulfate. Fly ash thus lends the concrete properties that are required especially for bridges, tunnels, cooling towers, sewers and foundations.
How is fly ash produced?
Fly ash originates during the combustion of hard coal when the non-combustible, mineral components of the coal are filtered out of the flue gas in the electrostatic precipitator. A fine dust of mineral particles is created, very similar to those occurring naturally, such as volcanic ash or earths. Fly ash is produced in modern hard coal-fired power plants throughout the world. Using fly ash as a clinker substitute in cement or as a cement replacement additive in concrete can reduce the ecological footprint of the respective cement or concrete per metric ton of fly ash used by a clearly measurable amount of CO2.
To ensure its quality, we have the material properties of the fly ash regularly examined in our Construction Materials Laboratory .