Fly ash in Concrete

Fly ash has become a big part of the precast concrete industry. It is a useful addition to the cementious portion of a concrete mix. Because of its unique molecular shape it makes stripping molds off of dry cast products smoother, aids in longer product lives in certain applications, and beacause it is a by product of burning coal utilizing it within concrete is a beneficial way to capture and store an otherwise harmful material. But what is fly ash?

As I mentioned fly ash is usually a by product of burning coal. However fly ash is technically any ash, typically from a furnace that is airborne. Fly ash is usually used to replace 15-25% of the cementious material in a concrete mix. There are several benefits to using fly ash. A key one is that fly ash has excellent resistance to acids and its use in a concrete mix helps the product to resist the premature degradation caused by exposure to excrement and other acidic organic materials that can be found in the soil.fly ash is also resistant to sulphate and salt.

The round shape of the fly ash molecule adds an elegant elasticity and smoothness to the concrete mix. This is a great asset when pumping concrete and when stripping dry cast products in their green state.

Unfortunately, or fortunately, based upon your view point, Fly ash has become very difficult to get due the combination of an increased demand by concrete producers and, more significantly, greater environmental restrictions on the production and consumption of American coal.