Cementing Solutions

ECU researcher explores sustainable concrete production

An East Carolina University construction management researcher has published work that describes a more sustainable process to produce concrete.

Dr. Amin Akhnoukh worked with Natrx, a Raleigh sustainable technologies company, to show how dredged river clay could result in stronger concrete that is friendlier to the environment.

Akhnoukh said current concrete production requires high-energy consumption and produces significant carbon dioxide emissions. The quest to reduce that environmental footprint mirrors that of Natrx, which provides nature-based coastal protection alternatives and has deployed 50,000 tons of biogenic living shoreline barriers that protect against coastal erosion.

He said Natrx CEO Leonard Nelson and President Matthew Campbell approached him about using clay dredged from the York River in Virginia as a contributing compound in concrete. Unlike sand that is dredged from shipping channels and used for beach renourishment, dredged material from river bottoms is usually disposed, Akhnoukh said. Natrx wanted to explore its use in creating what it calls EcoForms, an ecofriendly barrier that provides shoreline protection and promotes habitat growth.

“I told them we could give it a shot,” Akhnoukh said.

Initial results didn’t look promising.

“We started by using the material as is, and it was not very successful, so we ended up with the calcination,” Akhnoukh said.

Calcination is a process that involves heating a substance to a high temperature. The calcinated clay was used to replace some cement in the concrete mixture, and Akhnoukh tested various combinations of materials.

“We tried doing partial replacement of cement using 10% replacement, 20% replacement and 30% replacement. The most promising numbers are around the 20% replacement,” he said.

Akhnoukh said using 20% of calcinated clay to replace the cement used in concrete mixes produced a stronger product on top of cutting its carbon footprint by about a half.

“It’s a recycled material and recycling is always good,” Akhnoukh said. “It’s a possible alternative to cement, and the more we introduce cement alternatives to our concrete mix, the better off and greener our product will be. The more we incorporate these materials, the less cement we consume and the less carbon dioxide is emitted to the environment.”

The Associated Schools of Construction International Conference and the American Concrete Institute published the research results.

The work isn’t done though, Akhnoukh said.

“We have some initial results of how promising the material is and some compressive strength results,” he said. “Leonard Nelson is thinking about proceeding with more larger scale testing to have a full understanding with everything, and we’re still looking for a more economical way to do the calcination.”