BACK TO BASICS: FRAP: Take It From Me! Tim Boone, President, National Asphalt Manufacturing Corp. Fractionated Recycled Asphalt Pavement, or FRAP, has been gaining more attention as the asphalt industry strives to lower its carbon footprint. For many of us, however, FRAP is nothing new. Many companies, such as National Asphalt Manufacturing Corp., have produced new asphalt mixes using FRAP for years. These mixes, examined through the lens of Environmental Product Declarations (EPDs), have a lower global warming potential (GWP) due to higher recycled asphalt contents and less virgin asphalt binder/aggregate. An Example from the Industry National Asphalt is a single-plant asphalt manufacturing company based in Fairfax, Virginia. Until 1984, we operated an outdated batch plant that could no longer keep up with our customers’ demands. Things in our industry were starting to change. Advancements in plant technology were making great strides. Transportation departments nationwide were beginning to mill off the wearing coarse of asphalt instead of just overlaying it. Milling was creating a product that had little use. It was being landfilled or disposed of in other ways but rarely utilized in newer mixes. The industry recognized the potential use and value of milled asphalt material, including stone and liquid asphalt, and after much research and testing asphalt recycling was finally approved by local transportation departments. In 1985, inspired by these advancements, we decided to upgrade our entire facility to a state-of-the-art parallel flow drum plant that could incorporate recycled asphalt. We also installed a recycled asphalt product (RAP) processor to break apart, sort, and screen the broken and milled asphalt. This was all new technology, and it became a game changer for us and the asphalt industry at large. For years, millions of tons of old, wornout asphalt was thrown in landfills or anywhere else contractors could dispose of the material. Instead, we could allow our customers to bring in old asphalt, and we could then process and incorporate a percentage of it into our mix. By adding environmental and economic stewardship to its focus, the industry has helped turn asphalt into the most recycled product in the United States. The Virginia Department of Transportation (VDOT) initially allowed 10–15% RAP in mixes. We operated under this allowance for many years, processing our RAP into two sizes: a “coarse” product sized at 1.5 inches and a “fine” product sized at nine-sixteenths of an inch. As VDOT became more confident in the quality of RAP mixes, they raised the percentage allowances. However, our parallel flow drum was not designed to produce higher percentage RAP mixes, so we upgraded the National Asphalt facility again to an Astec Double Barrel with better mixing capabilities along with lower air emissions to meet the changing industry. With this upgrade, we began producing mix with an average of 25% RAP. Production seemed to run smoothly, but our Quality Control (QC) Director soon approached me with concerns. The consistency of the mix was all over the place. One sample would be coarse with a high asphalt concrete (AC) content; the next would be fine with a low AC content. In other words, we were struggling to keep our material within specification. The quality of our mix was in jeopardy unless we could find the cause. However, the only thing that had changed in our production was the percentage of RAP. Reducing the percentage of RAP was not an option, but the variation we saw in our gradation and liquid AC could not continue. A short time later, I was able to have a conversation with Astec founder Dr. Don Brock while visiting the Astec headquarters in Chattanooga, Tennessee. During our conversation, I mentioned the issues we were experiencing with mix inconsistency using higher RAP. Don asked me if we “fractionated” our RAP. After seeing the puzzled look on my face, he began to tell me how to screen our finished RAP differently. He then challenged me to go back and test our unprocessed RAP pile and find out what it contained. Once we had that information, he suggested we break the material down to a minimum of two sizes, though three or more sizes would be more beneficial. After my visit with Dr. Brock, I returned to our facility and had our team examine our RAP product to find out what was in our pile. What we found was that over 95% of the millings and broken asphalt we were getting from our customers was surface mix, with a top-size material of one-half to nine-sixteenths of an inch stone. So, the 1.5inch material we produced through our RAP processor resulted in clumps of one-half-inch minus material. To address this, we needed space to store two or more finished products. The problem? WE had no additional space, limited as we were to our facility’s 2.5 acres. We decided to replace our existing screening unit with a larger twodeck model and change how we screened the finished products. We eliminated the 1.5-inch material and limited the top size to nine- sixteenths of an inch. The smaller material now had a top size of one-quarter of an inch. Once we began producing material at these sizes, I had my QC Director test the finished products extensively. The nine-sixteenths material was very clean, comparable to a #8 stone, with a minimal amount of fines to it and a liquid AC content averaging 4.5%. The quarter inch material was comparable to a #10 stone, commonly known as stone dust, averaging 7.2% liquid AC. Overall, the products’ consistency meant we could blend them into our mix with little to no variability. From the moment we began producing material with our fractionated RAP, the variability in our gradation and asphalt contents causing QC issues became a thing of the past. Not to mention, the GWP of our surface mixes dropped below 50, with our base mixes even lower! The Benefits of FRAP Investing in fractionating our RAP has been a huge win for National Asphalt and the industry more broadly. Mix quality and consistency are a high priority: National Asphalt wants to produce the highest quality product, something that our customers can count on to be the same today as tomorrow. Now that we control every component of our mix, that is exactly what they get. VDOT specifications now allow 30% RAP in surface and intermediate asphalt mixes and up to 35% RAP in our base mixes. I believe that even higher RAP percentage mixes are coming. When they do, we’ll be ready. VAASPHALT.ORG 25
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