See-Through Concrete May Give Ordinary Folk Superman Powers

It used to be only Superman who could see through concrete walls, but an exhibition at the National Building Museum shows that mere mortals can do it too.

Called “Liquid Stone,” the show features variations of translucent concrete, a newfangled version of the old construction standby that offers a combination of aesthetics and practicality.

One display is a wall of translucent concrete blocks. When someone stands in front of it and light is shone from behind, the person’s shadow can be seen on the other side.

“I think it’s beautiful in itself, so it might be attractive in a restaurant or a hotel,” said G. Martin Moeller Jr., the museum’s senior vice president. “But it might also be used in an indoor fire escape where you wanted light to come through in case of a power failure. It could become a lifesaver.”

The translucent blocks are made by mixing glass fibers into the combination of crushed stone, cement and water, varying a process that has been used for centuries to produce a versatile building material. The process was devised by Hungarian architect Aron Losonczi in 2001.

“The idea came from a work of art I saw in Budapest,” he said from Csongrad in southeast Hungary. “It was made of glass and ordinary concrete, and the idea of combining the two struck me. Then I went to Stockholm to do postgraduate work in architecture and it developed there.”

One of the first demonstrations was a sidewalk in Stockholm made of thin sheets of translucent concrete. It looks like an ordinary walkway by day but is illuminated at night by lights beneath.

A company in Aachen, Germany, called LiTraCon for “light transmitting concrete,” makes translucent blocks and plans to have them market-ready this year. Andreas Bittis, in charge of marketing, said that thus far, they had mainly been used in demonstration projects, such as the Stockholm sidewalk.

Bittis has many ideas for practical uses.

“Think of illuminating subway stations with daylight,” he said in an e-mail. Or using the concrete for speed bumps and lighting them from below to make them more visible at night.

Translucent concrete is strong enough for traditional uses of concrete, and chemical additives can increase the strength. Moeller pointed out, however, that until demand increases, experimentation continues and production costs fall, the price will be higher than similar older products.

Will Wittig, who teaches architecture at the University of Detroit Mercy, developed concrete panels shown in the exhibition that are only a tenth of an inch thick in places. He said he had ideas about an all-concrete building, part of which would consist of ordinary opaque concrete and the translucent kind.

Inventor Thomas A. Edison had the idea of an all-concrete house almost a century ago. Although he worked on it for years and spent a lot of money, the idea never caught on.

Today’s concrete buildings have skeletons of steel, but Moeller said that could become obsolete with development of a recently invented self-reinforcing concrete.

The Lafarge Group, a French firm that says it is the world’s largest producer of concrete, sponsored the exhibition and was showing off a recent variety called “Ductal” that did not need steel reinforcement. The exhibition shows how a light-rail terminal has been built in Calgary, Alberta, almost entirely of Ductal, with concrete arches spanning 20 feet and the concrete only a quarter of an inch thick.

A smooth-textured, tubular sample is shown in the exhibition. Known to the museum staff as “the pretzel,” it looks like a hopelessly tangled garden hose.

Moeller said old-fashioned concrete had no give at all, but synthetic fibers added to the mix gave some flexibility without losing strength.

Lancelot Coar, an artist, architect and engineer in Washington, is working on the use of fabric as reinforcement since it’s more flexible than steel. The sample in the exhibition shows how it could give designers more freedom in using curved forms in concrete.

“Liquid Stone” will be on view though Jan. 23. Admission is free.