Green Asphalt Produces 100 Percent RAP
BY AsphaltPro Staff
Michael Capasso is first and foremost a contractor. As such, he tends to think that nothing is impossible.
That can-do attitude is what led him to launch Green Asphalt Co. in Long Island City, New York, in 2011 with one goal in mind: to produce 100 percent RAP asphalt mix with quality equal to or surpassing that of conventional asphalt.
Today, Green Asphalt’s 100 percent RAP asphalt mix is approved for use in New York DOT and New York City Department of Design and Construction projects, and Capasso has a new goal in mind.
“By 2038, our goal is to have all asphalt be 100 percent RAP,” he said. “Eventually, conventional asphalt will be green asphalt.”
Capasso’s motivations for producing 100 percent RAP mix were simple. “The environmental impact was number one,” he said, “but also addressing the issue of excess millings in the city and lowering production costs.”
The process of achieving that lofty goal was a bit more complex. The team at Green Asphalt quickly realized that they’d have to make significant changes to the way asphalt is produced.
“The perception that recycled asphalt means diminished quality is a result of producing recycled asphalt without changing the process of production,” said Nima Roohi Sefidmazgi, Green Asphalt’s vice president and head of business development. “We had to reinvent the wheel to determine what will work for 100 percent RAP.”
For example, asphalt plants have traditionally crushed RAP to one size in the past. That size was usually ½-inch minus, so it could be stored in a single stockpile. “If the quality of the aggregate isn’t very high, that will generate a lot of fines and dust in the crushed RAP, which introduces problems with the dust to binder ratio,” Sefidmazgi said.
Asphalt plants designed to run virgin material, which isn’t coated with AC, don’t have to worry about exposing that material to high temperatures over a direct flame, Sefidmazgi said, because that won’t generate any smoke and it doesn’t damage the material. “When using RAP, the material is already coated in AC, so the general process isn’t an option because it damages the valuable liquid AC coating the aggregates,” Sefidmazgi said. “The process has to be redesigned in a way to handle the high percent RAP.”
Additionally, Sefidmazgi said, it’s common to rely on super-heated virgin aggregate to then heat up the RAP. However, that doesn’t work as efficiently as RAP percentages increase.
“If you go over 30 or 40 percent, you’re relying on a much smaller mass of virgin aggregates to heat that RAP,” Sefidmazgi said. “Secondly, it’s very difficult to melt down that AC to consistently coat the RAP and virgin aggregates.”
“We are changing that mindset,” Sefidmazgi said. “Instead of trying to get 40 or 50 percent RAP with the old process, let’s invent an entirely new process where we can use all of the valuable AC in the mix.”
Green Asphalt first reached out to a couple of consultants who’d had experience with high percent recycled asphalt and began putting together a plant in Long Island City.
“The original plant was put together like a puzzle, with each piece coming from a different manufacturer,” Sefidmazgi said. “The plant that we built, you couldn’t buy off the shelf.” Each of the pieces is ‘off the shelf’, however Green Asphalt has changed the general process and plant configuration.
That process included a lot of trial and error, Sefidmazgi said.
They had to experiment with material processing, crushing, screening and stockpiling. They had to experiment with the heating system, temperature, buckets and flights. They had to experiment with handling less airborne particles and more fumes. And that was only the beginning.
“During this research and development state, we’d do things one way and fail, then another way and fail, and finally find success,” Sefidmazgi said. “A lot of what we do had to be invented as we went along.”
For example, Green Asphalt separates its RAP into various sizes, much like fractionating RAP into different stockpile sizes. However, most of the changes were to the burner, mixing and drying system, and the baghouse. The way they heat the RAP is different.
Instead of having a drying zone in which virgin material is superheated and a mixing zone in which it is then mixed with RAP under no direct heat, Green Asphalt heats RAP stone and sand throughout the whole drum at temperatures between 300 and 350 degrees Fahrenheit.
“The RAP gets heated by the hot gas coming from the flame,” Sefidmazgi said. “We pay attention not to let the flame touch the RAP.” To do this, they use refractory tubes and physically change the burner position to prevent the flame from touching the material.
“The last step on the equipment and production side was the development of a new baghouse system,” Sefidmazgi said. When virgin aggregate tumbles around in the drum, it creates airborne particles that must be captured in the baghouse. However, when heating RAP in the drum, the particles aren’t an issue, but fumes are, according to Sefidmazgi. “The filtering system in our baghouse is designed to take those fumes in,” Sefidmazgi said.
Also key to ensure mix quality is adding a rejuvenator. “We had to do a lot of research and experimentation on that to figure out what would work for 100 percent RAP,” Sefidmazgi said. They tried a variety of options and performed cracking and other tests before landing on the rejuvenator they now use.
“Most of what we’ve discovered, we own the intellectual property on,” Sefidmazgi said. “We were very fortunate to have the opportunity to take this risk, and invest the time and money to do this.”
Green Asphalt was also fortunate to have its sister company, CAC Industries, to test its 100 percent RAP mixes on its temporary paving jobs and provide feedback on product quality and performance.
CAC is a construction company working on infrastructure in New York City.
As Green Asphalt perfected its mix design, CAC was able to guarantee roads for a certain duration for its agency jobs. “They wanted us to prove it out,” Capasso said. “So if something went wrong, we were responsible for fixing it.”
That was the biggest challenge, Capasso said: convincing state and municipal agencies that a high-quality 100 percent RAP mix was possible.
Green Asphalt performed many test sections and pilot projects before its mix was approved by local and statewide agencies. Although New York state doesn’t allow high RAP mixes on the roads, they do allow it on shoulders, Sefidmazgi said. City agencies, he adds, allow use of 100 percent RAP on any application.
For example, they performed a pilot project on College Point Boulevard in Queens with two sections side by side, one with 30 percent RAP mix and the other with Green Asphalt’s 100 percent RAP mix. Six months after the job’s construction, Green Asphalt took cores and ran Hamburg and semi-circular bend (SCB) tests.
“Mixes showed satisfactory results using these tests,” Sefidmazgi said. “At the time, since there was no I-FIT test for SCB, we used Louisiana DOT’s method and criteria.”
“The proof is in the pudding,” Capasso said. “We’ve put our mix down all over the place and we’ve tested it in labs and on the streets. We’ve watched the wear and tear, we’ve done side-by-side road strips, and we don’t see any difference.”
In 2015, four years after the company was founded, it got approval for its mixes from New York DOT and New York City Department of Design and Construction.
“The majority of production in New York City is designed with the Marshall Method rather than Superpave, so we really had to work with agencies to look at performance-based mix design versus volumetrics,” Sefidmazgi said. “The state had to think about the process of approving a plant like ours.”
In the end, it was determined different enough to get a unique plant code, R0001, whereas other asphalt plant codes are typically an H followed by a five-digit number.
“The bottom line is you can design 100 percent RAP for any type of performance you want if you produce it the right way,” Sefidmazgi said. “The perception is that recycled material is low quality and leads to premature failures, but we’re making the industry understand that doesn’t have to be the case.”
Green Asphalt doesn’t have any virgin material in its operation.
“When you think about it, when you’re running 100 percent RAP plant, you’re really running an aggregate quarry and asphalt plant all in one because you’re making your raw materials that you’re using for production,” Sefidmazgi said. “Most places are making 30 percent or below RAP mixes, so that means if you mill up 100,000 tons of asphalt, only 30,000 is going back into your mix and 70,000 tons is going into a pile.”
“We’ve kicked the stockpiling issue in urban areas down the road and we need to deal with that,” Capasso said. And deal with it they did. In addition to alleviating the issue of stockpiles in New York City, Green Asphalt’s 100 percent RAP approach has also become a revenue stream.
In fact, Green Asphalt has a contract with New York City’s DOT to receive their millings.
“I know plants in less densely populated areas pay for millings, but here it’s the other way around,” Sefidmazgi said. “They pay us per ton of material. That’s really the case in a lot of urban areas because there’s nowhere to put those millings. It’s not valuable to put a pile of asphalt on the real estate here when you could do something more lucrative.”
According to Sefidmazgi, Green Asphalt accepts material for around half the cost of alternative options.
Sefidmazgi estimates that the DOT contract brings them around 85,000 tons each year. The remaining tonnage comes from Green Asphalt’s contractor customers.
“In the future,” Sefidmazgi said, “we will need to go back to our old roads as our quarries and refineries, and use that to make our new roads.” Green Asphalt, he added, is preparing for that not-too-distant tomorrow today.
Changing the World
Today, Green Asphalt has 15 employees and produces between 100,000 to 150,000 tons of mix per year, which is maximum capacity for their mix-and-match plant.
Today, between 70 and 80 percent of Green Asphalt’s mix is for public work, the rest, private. Prior to its approval in 2015, Sefidmazgi estimates that 90 percent of its production was private and the 10 percent that was public was exclusively test sections. And CAC continues to be Green Asphalt’s biggest customer, purchasing between 20 and 30 percent of its mix.
The next step in Green Asphalt’s master plan is to license its technology to convert existing plants to 100 percent RAP plants, Capasso said.
“The point we’re at right now is we’ve perfected our model in New York City and we’re going around the country to license this technology to other producers in metro areas: Boston, Chicago, LA, Seattle, Dallas,” Sefidmazgi said. That process also involves working with agencies to put in place quality control/quality assurance (QC/QA) processes they can trust to ensure that these products can be used on those agency jobs.
Sefidmazgi estimates that, depending on the type of plant, the cost to retrofit an existing plant to producing 100 percent RAP ranges from $750,0000 to $1.5 million.
“As fuel prices rise, the value proposition becomes much greater for what we’re doing,” Capasso said. “There’s this idea that if it isn’t broke, don’t fix it. People have been making money in our industry doing things one way for generations. There needs to be a willingness to change.”