Fly ash is a fine powder that is a by-product of burning pulverized coal in electric generation power plants.Fly ash is a pozzolan, a substance containing aluminous and siliceous material that forms cement in the presence of water. When mixed with lime and water, fly ash forms a compound similar to Portland cement. This makes fly ash suitable as a prime material in blended cement, mosaic tiles, and hollow blocks, among other building materials. When used in concrete mixes, fly ash improves the strength and segregation of the concrete and makes it easier to pump.

Other benefits include:

• Produces various set times
• Cold weather resistance
• High strength gains, depending on use
• Can be used as an admixture
• Considered a non-shrink material
• Produces dense concrete with a smooth surface and sharp detail
• Great workability
• Reduces crack problems, permeability, and bleeding
• Reduces heat of hydration
• Allows for a lower water-cement ratio for similar slumps when compared to no-fly-ash mixes
• Reduces CO2 emissions