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You’ve seen it. And you’ve wondered what it could possibly be good for. But those piles of recycled asphalt pavement (RAP) could be the material your road network needs to improve quality without breaking the bank... And it is just sitting there for the taking. 

Generated as part of many road reconstruction projects, RAP can be collected and stored in different ways. Some agencies store their RAP in large, co-mingled piles, while others maintain separation between stockpile quality.  While co-mingling RAP quality is fine for Hot Mix uses, this approach does limit your options when it comes to newer innovation in RAP applications.  

“It used to be that Hot Mix Asphalt was the primary use for RAP. In the last 5 years that’s changed,” says Dan Wegman, a pavement consultant and engineer at Braun Intertec. “Now there are new opportunities to use it... uses that save money for agencies. There’s no reason we shouldn’t recycle in place or put it in stockpiles to use in various applications later.” 

Because of its ability to be recycled, and the ever-increasing cost of asphalt, RAP has been called “black gold”. So what are some of the new ways to use this resource? When stored correctly, the possibilities (and savings) only increase.

Surface Treatments 

High quality RAP can be an excellent source of raw material for the aggregate used in surface treatments, including slurry seal and scrub seal. When crushed into a uniform shape, RAP acts like a pre-coated aggregate, which means it can be immediately put to work improving road networks-- and save big on the cost of material. 

Low Volume Roads 

On low-volume roads specifically, high quality RAP can be combined with gravel, emulsion and a chip seal. The reduced material cost can help produce a low-cost surface road. This approach uses engineered emulsions formulated to relevant climate specification. And, when partnered with a custom mix design, all of these pieces come together to make a big difference in road quality, at a small cost. 

Cold In-Place Recycling & Cold Central Plant Recycling

CIR and CCPR both recycle your existing pavement, making it easy and effortless to use the assets you’ve already paid for. Plus, they can result in big-time savings on trucking and hauling, especially in rural areas, where agencies would otherwise have to ship new asphalt from the nearest terminal. 

“Not only are you reusing your material, but you're less dependent on the cost of asphalt and your proximity to the nearest HMA plant,” Dan Wegman. , Principal Engineer at Braun Intertec said. 

Mohammed Sabouri, a Senior Engineer at Braun Intertec has been studying the effects of recycled material in the CIR process. 

“We started hearing from agencies that, when applied during hot weather, CIR required reduced emulsion content to assure constructability.” Sabouri’s emerging research has confirmed this reduction doesn’t necessarily affect quality. That could mean agencies don’t have to purchase as much emulsion in these situations. And in the long run, it allows substantial savings without sacrificing long-term road network performance. 

Store or Trade

Instead of stockpiling, some agencies may elect to sell RAP from old pavements to their contractors, in the hopes of getting a better price on the project. Although this is an option, agencies should consider the network value of their RAP before making the decision. 

Have a Plan in Mind

Every use for RAP can require different quality and grades, so it’s important to make the decision upfront how you plan to use the material in the future. When you stockpile, make sure you’re not  eliminating options for your assets, by combining high and low quality material into one pile. Several things to consider: 

• First, it’s important to mill existing pavement in the most effective way. Usually, the top 1.5 inches of any road will yield high quality RAP – the further down you go, the more variance you’ll get. But variance in materials shouldn’t stop you. Milling all the way below existing cracks  is the best way to prevent reflective cracking. 
• Then, you’ve got to decide what to do with your stockpile. After milling, it’s common that you’ll end up with segregations, which is when larger stones separate from the smaller aggregates. This usually happens naturally, as larger stones settle on the bottom when stockpiling the material. 
• If you’re just planning on using RAP in Hot Mix asphalt, storing various quality and size of RAP separately isn’t necessary. But mixing everything together limits what you can do with the RAP you just collected. With more precise processing, storage and separation, you have more options at your fingertips.  

“If I was an agency and I had the opportunity to collect RAP from a project, I would always keep it”, Wegman says. “The biggest reason people don’t know what to do with RAP is that they are unaware of the many ways to apply it to their network in the best way. There’s so much you can do with it when stored and processed properly.”  As pavement that can be used over and over again, RAP is 100% recyclable and should be considered very valuable to agencies. 

“In the utilization of rap, technology is always improving,” Wegman says. “It’s just a matter of contractor and agencies staying up to date on the research and new applications.” To learn more about recycled asphalt processes, visit the Recycling section of the Treatment Resource Center, or ask an ARRA expert directly.