Concrete consists of three parts: water, a cement which binds everything together, and an aggregate such as sand or gravel. That aggregate has to be mined from the ground, and is actually now in short supply in many parts of the world.

Discarded tires can be recycled to a certain extent, but often just end up sitting in landfills or getting burned.

Several groups have tried to address the one problem with the other, by substituting ground-up tires for a portion of the sand or gravel. The resulting concrete has tended to be tougher than regular concrete, as the rubber particles within it have allowed it to bend under pressure instead of breaking.