Concrete is one of the world’s most widely used building materials. It combines rock, sand, water and Portland cement into a single building product that can be used as walls, floors, stoops and holes.

While concrete is tough, it has a drawback: It is made with Portland cement, a key ingredient that generates more carbon dioxide than anything else in concrete except for the rock and sand. Now the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) has found a way to substantially improve the performance of concrete by using fly ash, an industrial byproduct created when coal is burned to produce electricity.

The resulting concrete has enough strength to support the weight of buildings and highways while containing up to 50 percent fly ash by volume. Although fly ash can significantly reduce the amount of Portland cement needed in concrete, until now it has been difficult to make strong concrete that uses more than 25 percent of this material.

Concrete is one of the world’s most widely used building materials. It combines rock, sand, water and Portland cement into a single building product that can be used as walls, floors, stoops and holes. The cement in concrete is a mixture of limestone and clay that is “cooked” at high temperatures (2,700 degrees Fahrenheit) to form a silicate called clinker. When mixed with water, the clinker produces a thick paste that binds sand and gravel into strong stone-like material.

According to the U.S. Environmental Protection Agency, more than 100 million tons of fly ash is produced annually in the United States. This byproduct of coal-fired power plants is a fine powdery material composed primarily of silica and alumina along with some carbon and trace amounts of other minerals. For several years, it has been used as an additive in concrete to make structures stronger and more durable.

A little known fact is that fly ash, a coal combustion by-product (CCP), can be used in concrete. Fly ash has been added to concrete since the early 1930s. Each year more than two million tons of coal combustion residuals are utilized in concrete products in the United States. Fly ash can improve the performance and quality of concrete while also offering environmental benefits and providing cost savings to producers.

Fly ash is produced when bituminous or sub-bituminous coal is burned at electric power plants. Typically 35 percent to 65 percent of the raw material is burned away before it becomes fly ash. As an alternative to landfill disposal, fly ash may be recycled into concrete products or other end uses such as agricultural lime or mine reclamation projects.

Because fly ash can be utilized in concrete mixes, it can reduce the amount of Portland cement needed for construction projects – reducing costs and emissions from the production of Portland cement.

A DNR project manager who was asked to make a presentation about fly ash said, “It’s just concrete.” However, what he didn’t say is that fly ash concrete is more durable and resistant to the elements than standard concrete.

Fly ash is a byproduct of coal-burning power plants. The Environmental Protection Agency (EPA) has promoted the use of fly ash in concrete because it reduces landfill pollution. According to the EPA, “coal combustion residuals (CCRs), commonly known as coal ash, are the second largest industrial waste stream in the United States.” The EPA estimates that more than 130 million tons of CCRs are generated each year.

The EPA allows safe disposal of CCRs at “beneficial uses” such as concrete and other building materials. The agency also requires that all new landfills receive one foot of compacted clay on its impermeable liner before accepting any new coal ash.

Concrete Made with Fly Ash Is Longer Lasting

A recent study by the National Association of State Departments of Agriculture revealed that fly ash is not only good for landfills and environment but also good for construction projects large and small. Travelers driving past miles of cornfields along Interstate Highway 57 between Champaign and Kankake

The production of Portland cement releases large amounts of carbon dioxide, a greenhouse gas. Fortunately, there are alternatives. One is fly ash, a by-product of burning coal in power plants. According to the U.S. Environmental Protection Agency (EPA), fly ash can potentially replace some or all of the Portland cement in concrete, reducing its environmental footprint.

Fly ash is collected from the exhaust gases in a power plant’s filters and electrostatic precipitator; it is usually carried away by trucks on conveyor belts, or pumped in pipes as a slurry or dry form (usually called pond ash). This fly ash is typically stored in ponds until it can be put to use.

The EPA estimates that between 50 and 70 million tons of fly ash are generated every year in the United States alone. About half of this goes into concrete, replacing up to 30 percent of the Portland cement that would normally be used. It improves concrete’s strength, durability and ability to resist water penetration and alkali silica reaction (also known as ASR, or “concrete cancer”).

Because fly ash is a by-product from existing industries, it costs less than Portland cement; if it is not reused it has to be disposed of somehow—in landfills perhaps—

Fly ash, a coal combustion by-product, has been recognized as a quality alternative to Portland cement in making concrete. The use of fly ash in concrete improves the workability and finish ability of fresh concrete, while improving the strength and durability of hardened concrete. Research has shown that fly ash can improve resistance to freeze-thaw damage, chemical attack and corrosion.

The use of fly ash in construction is environmentally responsible because it reduces waste sent to landfills. Since its introduction into the marketplace in the 1930s, coal combustion products have helped build America. Indeed, today more than 60 million tons are used annually in a variety of beneficial applications.

Fly ash is a fine powder recovered from gases created by the burning of coal during electric power generation at power plants. Fly ash is commonly used as an ingredient in hydraulic cement (Portland) concrete produced with Portland cement. It contributes to the long term strength gain and durability of concrete.

Overall, concrete is the second most consumed substance on earth, only surpassed by water. But concrete is not just a building product; it’s also one of the world’s most important infrastructure materials. Buildings, homes, bridges and roads are all made out of concrete.

The Portland Cement Association (PCA) says that Americans use about 95 million tons of Portland cement each year. It’s used to make concrete for driveways, patios, highways and airport runways. The problem is that making Portland cement requires enormous amounts of energy.

According to the PCA, making one ton of Portland cement generates about a ton of carbon dioxide gas. That’s about 10 percent more than what a coal-fired power plant produces generating enough electricity to power your home for a year.

But there may be an alternative to Portland cement: fly ash.

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