Concrete comes alive

Researchers have created a living, self-replicating form of concrete, reports SmithsonianMag.com. The team from University of Colorado, Boulder tweaked the traditional concrete mix of sand, cement, and water, instead combining sand with gelatin, liquid nutrients, and cyanobacteria, microbes that use sunlight to make their own food. Using molds, the researchers created arches, cubes, and shoebox-size bricks, all of which started out green—because of the bacteria’s photosynthetic properties—then turned brown as the concrete dried. A 2-inch cube of the living material is strong enough for a person to stand on, although it is still weak compared with traditional concrete. But the material has a big advantage over the traditional gray stuff: it can grow. When the researchers split a brick in two and placed each half in a mold with some additional sand and nutrients, within seven days they had two bricks instead of one. The Department of Defense is interested in these living building materials, which could aid construction in remote environments. “Out in the desert,” says lead author Wil Srubar, “you don’t want to have to truck in lots of materials.”

■