Concrete Transmits Light

LiTriCon has been around for a few years now, but it still sounds like science fiction to those who think of concrete as massive, opaque and heavy. Essentially, LiTraCon is a fine concrete mix with about 4% of its volume taken up with optical glass fibres. What you end up with is translucent concrete, that is, concrete that light and shadows can be transmitted through.

This blog has good summary of what it is and where it's heading:
http://greenlineblog.com/litracon-light-transmitting-concrete/

Of course you don't get complete tramsission of the scene behind the wall, but you do get the play of light and shadow, the shadows of leaves or people walking by. So instead of concrete becoming a visual barier, it's suddenly opened up. The uses in architecture are immediately obvious, but in small-scale work lamps and light surrounds come to mind, and LiTraCon is already making those for sale.
http://www.litracon.hu/

Andreas Bittis in Germany is also making "translucent concrete," so it appears this is a trend.
http://www.andreasbittis.de/
And here's a third one:
http://www.luccon.com/