Engineering: Turning Waste Into Concrete

The world’s most utilized construction material is concrete, made when cement is mixed with water, gravel, and sand. The process of making cement releases more than 3 billion metric tons of carbon dioxide into the atmosphere, accounting for 5 to 8 percent of the carbon dioxide produced from human activity. Professor Claire White is working to demonstrate the durability of a type of concrete that is made without cement and that results in the release of very small amounts of pollutants.

White, an assistant professor of civil and environmental engineering, leads a team at Princeton’s Andlinger Center for Energy and the Environment that is studying concrete made from slag, a waste byproduct produced mainly from steelmaking. White is examining its structure at the molecular level to understand the formation of micro-cracks, which can compromise long-term stability. She also is working with an Australian company, Zeobond, that is developing sustainable concrete-production methods.

Concrete made from slag is not new. “The former Soviet Union invented the technology in the 1960s, and there are still buildings made from it standing today,” White says.

Since 2006, Zeobond has made roads and buildings using the material, including its own headquarters. The U.S. Army also has used the concrete for airport-runway repairs. But while those projects were successful, alternative cements have not taken off, in part because the building industry is conservative, says George Scherer, a Princeton professor of civil engineering. White is working to create new international building standards to boost the use of environmentally sustainable construction materials. Says Scherer: “Claire is using fundamental science to solve a practical problem.”