It’s often a struggle to actually recycle everything that can be recycled- for instance over 90% of all plastic goes unrecycled- but there is one material that is able to be 100% recycled. This material is the asphalt from roads and roofing shingles, known as reclaimed asphalt pavement or RAP. According to the Federal Highway Administration, over 80 million tons of asphalt is reclaimed from pavement each year, and the entirety of it is recycled into new pavement.
What is Asphalt?
Asphalt has been around longer than expected, with the ancient Babylonians using it to build roads, where it was prized for being able to reduce dust and mud and provide a durable surface. Asphalt is made when a binding material called a bitumen is mixed with an aggregate, typically rock or sand. Modern advances have also allowed the aggregate to consist of ground tire rubber, foundry sand, glass, plastic, and even corn stalks and plant material.
Asphalt can be recycled so well because the bitumen acts like a glue that can be reactivated when it’s heated, allowing it to be reused over and over. Research has found that older, reclaimed asphalt actually has a higher quality than brand new asphalt.
The majority of recycled asphalt pavement comes from roads being resurfaced to fix wear or potholes, where the asphalt surface is milled off to provide a better surface for the new overlay of fresh asphalt. This asphalt is then sent to be ground up, and the aggregate is screened out to be reused in the fresh recycled asphalt. The ground asphalt is washed to remove any dirt and organic material that would compromise the structure when used as a road, and then the material can be heated, dried to a specific moisture content, and cooled while any needed additives are mixed in.
The clean and dried ground asphalt bitumen is then fed into hot asphalt recycling machines as needed, which heats the bitumen up to the point where it becomes a sticky glue again, and adds the aggregates to create hot asphalt, ready to be spread onto the road base to create a clean, smooth surface.
Recycling all of this asphalt keeps over 50 million cubic yards of landfill space from being filled each year, and is estimated to save over $2.5 billion in taxes each year. It also help prevent new bitumen from having to be mined and processed at a higher rate, which is a water and energy intensive process.