Products : Fly Ash / Pozzolanic Materials

Fly ash is defined in Cement and Concrete Terminology (ACI Committee 116) as: “the finely divided residue resulting from the combustion of ground or powdered coal, which is transported from the firebox through the boiler by flue gases.” It is a by-product of coal-fired electric generating plants.

Fly ash offers the market two major advantages:

1. Environmental Advantages: by diverting the material from the waste stream, reducing the energy investment in processing virgin materials, conserving virgin materials, and allaying pollution; and,

2. Performance Advantages: Fly Ash improves the performance and quality of concrete: improved workability, reduced water demand, reduced segregation/ bleeding, lower heat of hydration, increases strength, reduced permeability, reduced corrosion of reinforcing steel, increased sulphate resistance, and reduced alkali-aggregate reaction

General properties of fly ash vary from each plant according to the coal source/ type and the several key production factors/ systems.

Coal Types:

There are generally 4 types of coal: Anthracite, Bituminous, Sub-Bituminous, and Lignite.

In general, all four coal types can produce fly ash that can be used in concrete and concrete products. However, the properties of the fly ash

change as the coal source changes.

Production Factors:

There are generally three (3) systems for burning of pulverized coal in a power generation. Each system uses a different temperature to burn the pulverized coal.

1. High temperature furnace (Pulverized Fuel Combustion).

In this system coal is crushed to a very small size. And then sprayed with air into the furnace. The coal fire then heats the boiler producing steam and the steam spins a turbine generator. This is the most modern system now commonly used.

The furnace temperatures in this system can be as high as 1,500 - 1,700 degrees Celsius (Cyclone Combustion). Although there is typically only a low volume of fly ash produced, the fly ash is shaped like glass beads (vitreous particle).


	2. Medium temperature furnace (Pulverized Coal Combustion)
	In this kiln-fired pulverized coal system (Pulverized Coal Combustion) furnace temperatures range of 1100-1400 ° C. This system produces a good and consistent fly ash.


	3. Low temperature furnace (Fluidized-Bed Combustion)
	Temperature in the furnace is relatively low - at less than 900 degrees C. The fly ash from this system is generally irregularly shaped

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