A Concrete Plan

A revolutionary—and greener—material could have buildings rising from the ashes

ASH USUALLY CONJURES IMAGES

of destruction, not construction. But a new plan might change that. By mixing volcanic ash with concrete, a team of international scientists created a material that can be used for the construction of buildings. Best of all, it’s a greener alternative to concrete.

The production of traditional concrete accounts for about 5 percent of the world’s carbon dioxide emissions, mostly because of the heat required to manufacture it. “It’s a very high-energy, intensive process,” says Kunal Kupwade-patil, who researches building materials at the Massachu- setts Institute of Technology. Volcanic rock, by contrast, requires few resources. “Collect the volcanic rock, grind it into ash—that’s it.”

Kupwade-patil and colleagues at Kuwait University and the Kuwait Institute for Scientific Research tested various combinations of the concrete and ash mixture—using more or less pulverized volcanic rock ground to different levels of fineness—to see which reduced the toll on the environment without sacrificing building strength. The findings were striking. Compared with traditional cement, concrete made with equal parts volcanic ash and cement required 16 percent less energy to construct a neighborhood of 26 concrete buildings. Furthermore, the finer the ash, the stronger the concrete. The study was published in February in the Journal of Cleaner Production.

This building material of the future could be customized according to its use. Tall buildings, the researchers note, need stronger concrete, so that mixture would use the finer ash, which reacts more easily with the cement. Concrete walls, demanding less strength, could use coarser ash and more cement.

Using volcanic ash does have some environmental impact. Rocks emitted by volcanoes aren’t smashed into powder naturally, says Oral Büyükoztürk, the study’s senior author and a civil and environmental engineering professor at MIT. “Obviously, an effort is required to grind them to a level that can be used in the mixture.” But, he adds, the process requires far less heat than the production of traditional cement.

The approach pays off in other ways. Integrating ash into concrete makes use of what would otherwise be a waste material. And sourcing the ash locally—from nearby volcano sites—eliminates the need to transport materials over a great distance. The Kuwait study illustrates that point: The investigators imported their volcanic ash from neighboring Saudi Arabia.

Amplify the energy (and therefore cost) savings seen in the laboratory to a life-size scale, says Büyükoztürk, and the opportunities for modernday construction projects could be impressive. “There may be a tremendous implication of energy savings at the city scale.”