The most common use of fly ash is as a partial replacement for portland cement used in producing concrete. Replacement rates normally run between 20% to 30%, but can be higher. Fly ash reacts as a pozzolan with the lime in cement as it hydrates, creating more of the durable binder that holds concrete together. Fly ash concrete is easier to work with because of its spherical shape and its ability to moderate early concrete set time. The improved flowability, reduced hydration temperatures and delayed setting time of fly ash concrete are the main factors that contribute to ease of placement of concrete. Fly ash concrete also has lower permeability than traditional concrete, which means less water and chemicals can enter the concrete. Therefore, fly ash concrete has a longer service life and doesn’t need to be repaired or replaced as often.
At Glenmine Minerals, we offer two varieties of Fly-Ash to our customers :
1. Class F Flyash :
The burning of harder, older anthracite and bituminous coal typically produces Class F fly ash. This fly ash is pozzolanic in nature, and contains less than 7% lime(CaO). Possessing pozzolanic properties, the glassy silica and alumina of Class F fly ash requires a cementing agent, such as Portland cement, quicklime, or hydrated lime.
2. Class C Flyash :
Fly ash produced from the burning of younger lignite or sub-bituminous coal, in addition to having pozzolanic properties, also has some self-cementing properties. In the presence of water, Class C fly ash hardens and gets stronger over time. Class C fly ash generally contains more than 20% lime (CaO).