In 2022, Ryan Smith of Columbus-based RAP Management met with the Ohio Department of Transportation (ODOT) to discuss the possibilities of reclaimed asphalt pavement. Smith had recently purchased an Ammann high recycling technology (HRT) batch plant, and desired to experiment with high-RAP mix consistency. Specifically, the mix he would be using contained 55 percent recycled material.
Before the meeting, RAP Management completed a Roads & Bridges virtual event which featured a demo project. Here, ODOT expressed interest in the project and joined forces with Smith to try the high-RAP mix alongside of each other.
The current trends in the asphalt industry is using measurable tests to see how materials will perform in the field. Smith says, “Our goal was to show ODOT that we could deliver a product equal to what they were currently using.”
Eric Biehl, Ohio’s State Asphalt Materials Engineer, also wanted to know if that was possible. “My overall objective was to see how a 55 percent RAP mix would place compared to a normal medium traffic mix. My hope was that the long-term performance would be the same, if not better.”
In order to conduct the experiment, ODOT decided that the southbound lanes of a 4.6-mile section of State Road 664 will be paved with 55 percent RAP, and the northbound lanes would be paved with a standard asphalt mix made of 20 percent RAP acting as a control.
The use of RAP provides economical and sustainable practices. RAP requires using fewer virgin materials. “It’s our ethical and moral responsibility to manage the product we’re generating,” says Smith, “and we can do that without sacrificing quality or cost.”
The balanced mixed design (BMD) approach, as established by a Federal Highway Administration (FHWA) task force in 2015, was utilized. According to the American Association of State Highway and Transportation Officials (AASHTO), BMD is an “asphalt mix design using performance tests on appropriately conditioned specimens that address multiple modes of distress, taking into consideration mix aging, traffic, climate and location within the pavement structure.”
Biehl notes, “It was ODOT’s first BMD project. That was exciting. We were very interested to see how BMD would work for mix design acceptance — and during production.”
In a perfect world, the asphalt mix would not rut at high temperatures and crack at low ones. The Hamburg Wheel-Tracking and Indirect Tensile Asphalt Cracking (Ideal-CT) tests were performed beforehand to assess the material’s resilience under these conditions. “Acceptance was based on asphalt content and gradation, as well as density gauge readings on the placed material,” explains Biehl. ODOT also collected buckets of both the RAP and the control mix, most of which were sent to the FHWA for evaluation.
CHALLENGES ALONG THE WAY
A major concern during the project was the distance between the RAP plant and paving site. Smith says, “Our material is perishable by temperature. The further the distance it has to travel, the more time it has to cool, and it needs to be installed above 250°F. ODOT’s standard is a limit of 50 miles between plant and site, and the mix must still be hot when it gets to the job so as not to pose problems with compaction.”
The control mix came from a plant just 16 miles away, while the RAP plant was 43 miles from the paving site. Concerns about maintaining the RAP’s mix temperature were proved to not be an issue. Fortunately, the mix stayed hot at around 325°F and no other issues came about.
The work was completed within a few days during August 2021. After QA testing being performed every 700 tons each day, the density of the two materials proved comparable. All in all, the 55 percent RAP mixed performed just as well, if not better than the control mix.
Smith states, “We exceeded all the specification requirements. We are able to mix to the highest standards, consistently and precisely.”
Biehl agrees. “Overall, we determined that high RAP mix can be produced and placed successfully,” he says. “And I think BMD will open the door to greater use of RAP in the future.”
DOING THE RIGHT THING
Smith notes that the Ammann technology from Switzerland dismissed the stigma that recycled materials equate to poor quality. “We felt we could actually develop a better product than what’s currently specified in the market while using recycled materials instead of virgin ones.” The ODOT project proved him right.
“I wanted my business to be something different,” he continues. “It’s just not sustainable to continue to mine quarries to produce virgin asphalt material. Now we know we can use a lot of the recycled product that would otherwise end up in a landfill and do it to the highest standards. The whole purpose of RAP Management is to use more of this material while delivering a top-quality product.”
Smith plans for his future to involve partnership with companies within Ohio and beyond. Increasing the use of recycled asphalt excites him about aligning sustainability and quality while being successful. The future is bright ahead.
“This is good for our infrastructure, for business and for the environment,” he says. “I feel blessed to be in a place where I can push this technology forward.”
*The original story was published by Roads & Bridge.
Powered by NAPA. “Reclaimed Asphalt: Paving the Way to Sustainability.” Roads & Bridges.