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Reclaimed Asphalt Pavement

The use of reclaimed asphalt pavement (RAP) in asphalt mixtures has been a widespread practice since the mid-1980s. The use of RAP in asphalt mixtures has significant economic,  environmental, and pavement performance impacts. 

By reusing the asphalt binder in the Recycled Asphalt Pavement (RAP), it is possible to consume less virgin binder which conserves petroleum. Likewise, the reuse of aggregate allows for less mining. Currently, there are about 18 billion tons of asphalt mixtures in U.S. roadways. Virtually all of this material is available for future generations to use. By using RAP instead of discarding it into landfills, we save about 48 million cubic yards of landfill space a year. That is enough to fill more than 12 Dallas Cowboys Stadiums. 

Milling the surfaces of pavements that need overlays is the primary source of RAP. A milling machine takes up the old surface by grinding it off and depositing the material into a dump truck for transport back to the plant. At the plant, the RAP may undergo sizing (fractionating) and further processing (screening) to get it to the right gradation for various mixtures. RAP is stored in stockpiles until it is needed. 

Not all RAP is the same.  RAP from airport runways and major highways typically has higher liquid asphalt content and higher quality aggregates.  RAP from parking lots,  patching, or older city streets typically have less liquid asphalt content and lesser quality aggregates.  For this reason, it is necessary to separate RAP before processing.

Treat processed RAP (fractionated and screen to size) as you would virgin aggregate. Stockpile RAP at the asphalt plant on a paved surface to help drain moisture away from the loading face.  Test RAP regularly for moisture, gradation, asphalt content, and deleterious material. If at all possible cover your RAP stockpile to prevent moisture as RAP and moisture do not go together very well.

Key Takeaways

  • Not all RAP is the same; separate it by type
  • Treat RAP as you would treat virgin aggregate stockpiling it in a paved area
  • Fractionate and screen RAP for a consistent blend
  • Know the properties of your RAP through regular quality control testing 
  • Keep moisture out!

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