Bright Future for Ancient Material
by Alexandra Goho
Each year, billions of tons of concrete become the stuff of buildings, highways, dams, sidewalks, and even artworks. The list goes on. Not only is the material ubiquitous, it has a long history. The Romans invented cement-based concrete more than 2,000 years ago and used the material to build architectural masterpieces such as the Pantheon. To Christian Meyer, a structural engineer at Columbia University, there’s just no question about it: “Concrete is the world’s most important material.”
And it’s one of the simplest. A typical mix of concrete consists of 60 to 75 percent sand and gravel or crushed stone, 15 to 20 percent water, and 10 to 15 percent cement, which is prepared by roasting limestone, clay, and other ingredients. The cement is the paste that binds the components into concrete.
There are many simple ways to modify the properties of concrete. Tweaking the ratio of the ingredients can change the material’s strength or roughness, for instance. Modern concrete also contains chemical additives that affect the material’s physical properties, such as the fluidity or the time it takes to harden.
Scientists and architects have been pushing the limits of this humdrum material to give it new features and creative functions. “Liquid Stone,” a current exhibit at the National Building Museum in Washington, D.C., portrays the future of
concrete. The show includes ultrahigh-performance concrete that bends like metal and another type of concrete that forms translucent blocks.
In pursuit of environmentally friendly construction materials, engineers are also giving concrete a hard look. Already among the most essential construction materials, concrete now seems poised to take on new roles.
Major suppliers of construction materials take a pragmatic approach to improving concrete. These firms are coming up with a stream of new mixtures, such as ultrahigh-performance, corrosion-resistant, longer-lasting concrete. “The future will see an increased use of [these materials],” says Steve Kosmatka of the Portland Cement Association in Skokie, Ill.
FACING THE FUTURE. A light-rail transit station in Calgary, Alberta, (above) and face sculptures adorning a condominium complex in Vancouver, British Columbia, (below) are made from new high-tech concrete materials.
For instance, consider some of the new materials developed by concrete giant Lafarge, headquartered in Paris. “Governments are finding they’re having to spend more and more on maintaining their infrastructure,” says Vic Perry of Lafarge North America. “That means you need to build things that last longer and are cheaper to maintain.” He’s talking about big things: bridges, highways, and buildings.
Perry leads the company’s North American operation producing Ductal, one of Lafarge’s newest concrete products. Unlike regular concrete, which is brittle and can rupture suddenly under a heavy load, Ductal can bend. “It will deflect and show signs of cracking before it fails,” says Perry. “You can see in advance that you’ve got a problem.”