Fly Ash

What is Fly Ash?

Fly Ash is an industrial by-product created from burning coal at high temperatures in electric generation power plants (power stations). In electrical production, pulverized coal is blown into the combustion chamber where it ignites, generates heat, and produces a molten residue. When this cools, the heavier particles, known as the slag,  drop to the bottom of the chamber. The lighter particles are known as fly ash and these particles remain suspended in the flue gas and are then extracted for further use.

Fly Ash has numerous industrial and construction applications. This material is a Pozzolan meaning that it contains aluminum and silicons that can form into cement when added to water. And the fact that Fly Ash is an industrial by-product means that it is considered environmentally friendly.

In addition fly ash has low embodied energy because it does not require high energy to produce and because it is so easy to ship and transport in bulk. This is unlike Portland cement for example which requires high temperatures and greater water consumption in production.

It is important to remember that fly ash is a by-product of the industry so if it did not have any further application, it would have to go to landfill thus adding to pollution. Fly Ash is approved by the FHA (Federal Highways Administration).


The types of applications for Fly Ash

Fly Ash is an adaptable useful material with numerous applications. It is often used in highway engineering including road construction, asphalt filler, embankments, mine fills, pavements, and sidewalks; anywhere in fact where Portland cement is usually the medium of choice. Replacing portland cement with fly ash is a cost effective alternative as it is much cheaper.

Fly ash also has numerous practical advantages over portland cement and is far easier to work with at cold temperatures.

Fly Ash is a very good alternative to portland cement. It can be added to cement or used as a material in its own right. It is extremely strong and durable and can withstand temperatures without cracking. It is considered a non-shrink material and produces a superior dense concrete finish with high detail. It increases the life of concrete structures because it improves durability and hardness.


The different types of Fly Ash

There are two commonly used types of Fly ash depending upon their chemical composition. Class C fly ash is derived from sub-bituminous coal.  This is lower grade coal that contains 35% – 45% carbon and is the type of coal most commonly used in steam-electric power generation. Class C fly ash It is sometimes known as high calcium fly ash as it contains more than 20% calcium oxide.

Class F fly ash is derived from bituminous coal and anthracites. It is generally higher in carbon and is low in calcium. It is sometimes known as low calcium fly ash.


Fly Ash is easy to transport, store and handle

Fly Ash is extremely easy to move, store and handle. It is usually stored dry in silos and can be transported in bulk via pneumatic trailers or any other bulk carrier via road, rail, or sea. It can be transferred via air slides or conveyors and can be pneumatically transferred via pipe lines.

Because Fly Ash is such a useful material, it is estimated that over 50% of concrete used today in the USA contains Fly Ash which has to be good news for the environment and for the economy.