Further information on Coal Combustion Products
Share |

Further Information on Coal Combustion Products

CCP's - What are they?

Coal is not all carbon. Coal contains quantities of non-combustible minerals. When coal is consumed to generate electricity, these minerals remain as ash products.

Fly ash is a fine, powdery material that would "fly” out of the power plant’s stacks if it were not captured. But power plants today collect their fly ash – and it can be a valuable tool in improving our environment and the quality of building products.

top of page

Ash Use ~ Yesterday and Today

The use of ash as a building material is not new. More than 2,000 years ago – long before the invention of portland cement – the Romans used volcanic ash to construct magnificent structures, such as teh Pantheon. Given the strength and durability of the volcanic ash "cement" they used, many of those structures are still standing today.

Modern interest in using coal fly ash as a cementitious product began in post-war Europe. By the 1950s and ’60s, power plants in the United States were collecting their fly ash for a number of beneficial uses.

Fly ash can be used in a variety of structural and low strength fill applications. It can be used as a mineral filler for paints, shingles, carpet backing and other products. It can be used in manufacturing mortars and stuccos. It even has various agricultural applications. But the largest application for fly ash is in the production of concrete.


How Fly Ash Works

Concrete is the most common building material in the world. Concrete is primarily a mixture of aggregates (rock and sand), cement and water. Compounds in the cement react with water to form a glue that binds the sand and rock into a solid mass.

When fly ash is added to the concrete mix, some of the cement can be eliminated. Mechanically, fly ash particles are small and spherical – allowing them to fill voids and provide a "ball-bearing” effect that allows less water to be used. Chemically, fly ash reacts with excess lime that is created when cement is mixed with water, creating more of the durable binder that holds concrete together.

The result is concrete that is more durable and stronger over time than concrete made with cement alone. Some of the benefits of using fly ash in concrete include:

  • Decreased permeability
  • Increased long term strength
  • Reduced damage from heat of hydration
  • Increased resistance to sulfate and other chemical attack

top of page

An Environmental Windfall

Using fly ash in concrete and other building products eliminates the need to dispose of the ash in landfills. When fly ash is used to replace cement in concrete, it has additional significant environmental benefits.

Fly ash use preserves natural resources by replacing materials that would otherwise be mined to manufacture cement. For each ton of cement produced, more than a ton of CO2 is emitted. When we replace a ton of cement production with a ton of fly ash, those greenhouse gases emissions are eliminated. Beneficial use of fly ash in concrete production reduced U.S. greenhouse gas emissions by approximately 13 million tons each year. Additionally, using fly ash and other CCPs saves energy because it reduces the energy needed to extract and process other materials for these same uses. But the good news doesn't end there. The beneficial reuse of CCPs also reduces the amount of ash that is disposed in landfills, meaning fewer disposal facilities need to be built.


What will it take to use more?

About 37 million tons of coal combustion products are beneficially used in the United States each year. But more than 81 million tons are still being disposed in landfills.

America’s power plants are investing in equipment and programs to collect, store and deliver ash products to the markets that need them. America’s railroads are transporting ash products long distances, making ash available in areas far from the country’s traditional coal regions.

Use of coal fly ash in concrete already has the support of a wide range of government agencies, including the Environmental Protection Agency, the Federal Highway Administration, the U.S. Army Corps of Engineers and the U.S. Bureau of Reclamation. Public and private entities can help by requiring the use of coal fly ash in their concrete and other building products.


Other Resources