Light-Transmitting (non-Opaque) Concrete

Chalk this one up to the "holy crap, that's cool" file. It's called Litracon and it's a mixture of concrete and glass optical fibers. It allows silhouettes to "shine" through the concrete itself and, more importantly, allows light to filter through.

Basically, thousands of the optical fibers are laid in parallel in between layers of standard concrete, creating the ability for light to seep through the otherwise gray material. This makes for shadow silhouettes or just plain light. This could greatly decrease the amount of energy used for both heating and electric lighting use during daylight hours.

It also makes for a less dreary concrete bunker, I'd say. Most of the properties of the concrete blocks remain unchanged, since the fiber optics make up only about 4% of the total volume.

Other options are also possible, including the use of recycled (powderized) concrete and even recycled fiber optic cables.

Pretty dang cool!