here's the product I envisioned using in my last project: LiTraCon. It's light-transmitting concrete (hence the name) that does so by embedding fiber optics (I mistakenly thought it was glass fiber) in concrete. Created by Hungarian architect Áron Losonczi, this stuff is pretty sweet. on the site it looks to be small modules, where I had envisioned my entire building to be a relatively monolithic pour, regardless of real-world feasibility.

LiTraCon homepage: http://www.litracon.hu/
where this image usually lives: http://www.techeblog.com/index.php/tech-gadget/light-transmitting-concrete