Since the first milling machines appeared on road-construction sites in the 1970s, these machines have evolved to become highly reliable and much less expensive to operate. The fact that the recyclable product created by milling machines is more valuable than ever, combined with the increased need for road surface rehabilitation to accommodate higher traffic loads, is resulting in a growing market for these machines.
Milling machines today can be seen as having two main purposes: The first is that of a “mining machine” capable of obtaining valuable material for the production of new hot mix, and the second is that of a surface-preparation machine that ensures the new surface course of a roadway can be made of the highest quality, because a new surface can only be as good as its base.
Equipped with cutter drums that are studded with teeth, modern milling machines can chew up old pavements to depths of up to 14 in. The removed old asphalt has become the most recycled product in North America.
“There was a time, 25 years ago or more, when people simply dumped things,” said Michael O’Connor, executive director of the Ontario Hot Mix Producers Association (OHMPA) in Canada. “If you were rebuilding a road, you would take the old asphalt and concrete and dump it some place, whether in a landfill or in the back of some property, and use new aggregates.”
The OHMPA promotes the use of recycled materials as ingredients in hot-mix asphalt pavements, and according to O’Connor, the prime material for recycling back into the road is the road itself. Crews can take broken concrete, crush it and reuse it as an aggregate beneath the driving surface. Reclaimed asphalt is also fully recyclable back into new pavement.
“You can send in a milling machine that actually grinds off the surface. Those grindings are perfect to recycle back into the same hot-mix that will go back down in the same project,” O’Connor said.
With milling, reclamation and recycling technologies improving and becoming more popular and cost efficient on road-construction projects, drivers can be sure they will increasingly be driving over recycled roads when they travel.