FLY ASH: THE MODERN POZZOLAN


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Power plants fueled by coal produce more than half of the electricity we consume today. But in addition to electricity, these plants produce a material that is fast becoming a

vital ingredient for improving the performance of a wide range of concrete products.

That material is fly ash.

 

Fly ash is comprised of the non-combustible mineral portion of coal. When coal is consumed in a power plant, it is first ground to the fineness of powder. Blown into the power plant’s boiler, the carbon is consumed — leaving molten particles rich in silica, alumina and calcium. These particles solidify as microscopic, glassy spheres that are collected from the power plant’s exhaust before they can “fly” away — hence the product’s name: Fly Ash.

 

Chemically, fly ash is a pozzolan. When mixed with lime (calcium hydroxide), pozzolans combine to form cementitious compounds. Concrete containing fly ash becomes stronger, more durable, and more resistant to chemical attack.

 

Mechanically, fly ash also pays dividends for concrete production. Because fly ash particles are small, they effectively fill voids. Because fly ash particles are hard and round, they have a “ball bearing” effect that allows concrete to be produced using less water. Both characteristics contribute to enhanced concrete workability and durability.

 

Finally, fly ash use creates significant benefits for our environment. Fly ash use conserves natural resources and avoids landfill disposal of ash products. By making concrete more durable, life cycle costs of roads and structures are reduced. Furthermore, fly ash use partially displaces production of other concrete ingredients, resulting in significant energy savings and reductions in greenhouse gas emissions.