[vonmoltke]

> And requires an underlying concrete layer to lengthen it's lifetime

Depends on the underlying soil. In north Texas it's common when asphalt is laid to pour a Portland cement concrete base, though many roads and highways are just straight concrete. In south Florida, the roadbed is usually just packed limestone, because the land has a rock layer no more than 50 feet down and the sandy soil is pretty incompressible, unlike the constantly expanding and contracting clay in Texas.