Burning rubber

Today’s road surfaces are created by mixing hot asphalt with sand, gravel or crushed stone before it is spread over the road surface. The Goodyear Tire and Rubber Company has patented a way to extend the lifetime of this surface (US 2003/203997). The asphalt, which binds the aggregate together, tends to be brittle and so breaks down over time. Goodyear says that adding sulphur and a polymer that combines styrene with butadiene rubber to the mix makes the asphalt more flexible and less likely to break down, so the road surface lasts longer.