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By Sara Hart

Innovation and the oxymoron

The fact that concrete is opaque is one of the indisputable physical attributes of the material. Of all of its intriguing, variable features, opacity has always been a given. Therefore, the concept of translucent concrete seems more than an oxymoron; it would seem to be an impossibility. And yet translucent concrete has been invented twice in the past few years. Time magazine recently named LiTraCon (www.litracon.com), a translucent concrete block, one of the “coolest inventions of 2004.” [Also see RECORD, December 2004, page 281.] (Apparently, the response to Time’s designation was so overwhelming that the company’s Web site collapsed from a stampede of curiosity seekers. At press time, the site was still down.)

 

Ricciotti’s Seonyu footbridge in Seoul is a major innovation in the use of ultra-high-strength concrete—in this case, Ductal. It spans almost 400 feet, is 14 feet wide, and yet the 4-foot-deep arch supports a deck that is only a little more than 1 inch thick. Photography: © Philippe Ruault

The material now trademarked as LiTraCon was invented in 2001 by a young Hungarian architect, Áron Losonczi, who combined concrete with an optical fiber from Schott (www.us.schott.com) to create building blocks that transmit light. The recipe calls for thousands of fibers, which run side by side, transmitting light between the two main surfaces in each block. Light rays enter the fiber at one end and are guided along the core by internal reflection, following all the bends in the fiber, which they exit at the other end.

According to the manufacturer, a wall created out of LiTraCon blocks can be quite thick, as the fibers work almost without any loss of light up to 60 feet, providing the same effect with both sunlight and electric light. Shadows on the lighter side will appear with sharp outlines on the darker one. Even colors of light are unaffected by transmission. The blocks will be on the market later this year.