After bituminous paving materials have been removed from a roadbed, they are hereafter referred to as recycled asphalt pavement or RAP.
It is generally known that the majority of existing roadways, both concrete and bituminous asphalt, undergo constant repair and surface overlay with new hot mix asphalt to achieve and maintain safe and comfortable high speed riding surfaces.
In recent years, new equipment has been introduced to the road paving industry in the form of pavement milling or grinding machines. The science of preparing an old roadbed base for new resurfacing is now commonly referred to as milling. Both state and Federal Department of Transportation (DOT) agencies throughout the country have readily accepted the science of milling.
The milling of old road surfaces provides a number of advantages in preparing the old roadbed for resurfacing. Milling not only ensures a new, smooth and level base for the new hot mix overlay, but at the same time lowers the road bed height to maintain bridge deck clearances and curb and gutter depths. Grinding or milling is also beneficial in removing potholes, old cracks, joint seams, and ruts along with other surface damage that would quickly reappear in a new surface overlay if not repaired. With many of the state and Federal DOT agencies now requiring the milling of road surfaces before permitting new overlay, there is an increasing inventory of asphalt millings being generated. The piles of discarded asphalt millings are becoming problems for land use, aesthetics and the environment. Attempts at reuse have proven difficult.
Needs exist for new recycling methods and apparatus for asphalt paving millings.