This special concrete tile allows light to pass through. The tile contains optical fibers that make up about 5% of its surface area. The fibers are distributed uniformly throughout the surface to allow an outline to be clearly visible on the other side. The tiles have the unique combination of being nearly unbreakable and translucent.
The material is made with a combination of optical fibers and fine concrete. It can be produced as prefabricated building blocks. Due to the small size of the fibers, they blend into concrete and become a component of the material like small pieces of aggregate. The result is a new material, which is homogeneous in both its inner structure and its surfaces.
The material is manufactured by alternating layers of concrete and fibers. The concrete sets and the material is cut into tiles. The pattern of the fibers can be uniform, or can be designed to a specification such as artificial wood grain.
Link to web page and text taken form Inventables