Casting Concrete in a Decorative Light
Thousands of optical fibers strands are placed in concrete to transmit light, either natural or artificial, into all spaces enclosed by the translucent concrete panels. Photo courtesy of Schott North America.
The fibers run parallel to each other, transmitting light between two surfaces of the concrete element in which they are embedded. Thickness of the optical fibers can be varied between 2 µm and 2 mm to suit the particular requirements of light transmission. Optical fibers transmit light so effectively that there is virtually no loss of light conducted through the fibers; in fact, it’s even possible to see colors through the concrete.
Translucent concrete achieves maximum effect when used in an environment with a high degree of light contrast, such as this illuminated table in a dimly lit room. Photo courtesy of Heidelberg Cement.
Originally, the fiber filaments were placed individually in the concrete, making production time-consuming and costly. Newer, semi-automatic production processes use woven fiber fabric instead of single filaments. Fabric and concrete are alternately inserted into molds at intervals of approximately 2 to 5 millimeters. Smaller or thinner layers allow an increased amount of light to pass through the concrete. Following casting, the material is cut into panels or blocks of the specified thickness and the surface is then typically polished, resulting in finishes ranging from semi-gloss to high-gloss.
The concrete mixture is made from fine materials only: it contains no coarse aggregate. The compressive strength of over 10,000 psi is comparable to that of high-strength concretes. However, due to the manufacturing process, elements for structural applications have not yet been produced.
A Glowing Future
Several years ago, the material was featured in the “Liquid Stone” exhibit at the National Building Museum, and started opening peoples’ eyes to all kinds of possibilities. While the material has distinct architectural and interior design appeal, some of the companies involved in light-transmitting concrete production envision using the distinct looks and unique abilities of this concrete for practical applications. Consider: one of the first demonstration projects in Stockholm was to light sidewalks at night. Now people are thinking about increasing visibility in dark subway stations with the material. And there are several potential safety applications being discussed, such as lighting indoor fire escapes in the event of a power failure or illuminating speed bumps on roadways at night. Surely, as more people see its potential, light-transmitting concrete will become more and more visible.
References, Resources, and Manufacturers
- Light Transmitting Concrete
- Schott North America
- Translucent Concrete: An Emerging Material by Sara McGillvray, "Illumin," March 4, 2014.