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'Green' Concrete



The road to a sustainable future could soon be paved with green concrete.

Okay, not as enchanting as a road paved with gold. But since some 27,000 miles of road in the U.S. are made of concrete, it might be a step in the right directionso to speak.

How does concrete pollute when it just sits there? Well, it's in the manufacturing. The first part in making concrete is an energy-intensive process that creates carbon dioxide. It uses high-powered kilns to heat a mixture of limestone, sand, and clay, to 3,400 degrees Fahrenheit. This produces clinker, or "Portland cement," the gray powder that binds with water, sand, and gravel to make concrete.

"Green concrete" researchers avoid that energy drain by making cement without heat. At Louisiana Tech University scientists are using fly ash, a by-product of coal plants, to create synthetic cement. The California-based company, Calera [KAH-lehr-ah], goes even farther to make it green by sequestering fumes from coal plant smokestacks and mixing it with brackish water. This causes a chemical reaction that makes synthetic limestone. The process actually takes more carbon dioxide out of the atmosphere than it puts in.

Creating a road well travelled, and green.

Script by Gail Davis

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