"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."
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.
nstead of making concrete itself translucent, a small company in Germany is taking a different tack: incorporating transparent materials into the concrete. LiTraCon, based in Aachen, has developed a concrete that contains glass optical fibers the thickness of a hair. They transmit light from one side of the material to the other. Hungarian architect Áron Losonczi—who, like Wittig, experiments with construction materials—invented the translucent concrete.
To ensure that the ends of each fiber make contact with the surfaces on both sides of the material, blocks of concrete are built in stages. First, a thin layer of concrete is poured into a long, narrow mold. Then, a layer of optical fibers is laid along the length of the mold. After several repetitions, the resulting long beam can be cut into short, rectangular building blocks riddled with the thin light pipes, says LiTraCon's Andreas Bittis.
The fiber diameters range from 2 microns to 2 millimeters. By using fibers of different diameters, LiTraCon designers can achieve different illumination effects. Varying the size of the blocks, however, doesn't change the effect. So far, LiTraCon has made continuous concrete beams up to 20 meters long, and the fibers transmit light the entire length.
With these blocks, architects can design and build a large variety of structures, ranging from translucent concrete walls to floors lit from below. LiTraCon has already received a number of requests from architects interested in the material, says Bittis. One firm in New York has proposed using the new concrete in its design of a police college in Kuwait City. Because concrete is an excellent insulating material, the building would protect against the desert heat while letting through some sunshine. "
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