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Pavement recycling presents opportunities for cost reduction and environmental sustainability, according to the principal research scientist at the Virginia Transportation Research Council.
Brian Diefenderfer made the comments Feb. 11 during a presentation on a completed Interstate 64 project that involved pavement recycling. He was participating in a webinar hosted by the Federal Highway Administration.
The council is responsible for research activities at the Virginia Department of Transportation. And I-64 is a critical east-west freight route in the state, running from Hampton Roads through Richmond and Charlottesville and into West Virginia.
Also a heavily trafficked route, the stretch of I-64 Diefenderfer said he worked on sees 44,000 vehicles per day in each direction. Some 5% of these vehicles are trucks. The interstate forms a vital link to Norfolk, home to Naval Station Norfolk and Virginia’s major port.
The project represents the largest pavement recycling initiative in North America.
Paving work on Interstate 64. (Virginia Transportation Research Council)
Specifically, Diefenderfer’s work pertained to the second segment of a larger three-part effort to widen and reconstruct stretches of I-64. The second segment covered 7 miles of interstate and took place between October 2016 and April 2019. The third segment of the project, which spans 8 miles, is ongoing and slated to wrap later this year.
Over the course of the project for the second segment, about 519,000 tons of material were recycled, an estimated cost savings of about $10 million, according to Diefenderfer.
“Given the amount of material recycled and the high cost savings for this project, we really considered this project a success,” he said. “We really expect a long service life.”
The project was completed using a combination of full-depth reclamation and cold central plant recycling techniques.
Full-depth reclamation is an in-place recycling method that uses existing pavement materials as the base of the new roadway surface. The process involves pulverizing and blending layers of existing asphalt pavement.
Cold central plant recycling relies on reclaimed asphalt pavement that has been removed and stockpiled for later use to create pavement structures. Cold central plant recycling involves processing reclaimed asphalt pavement through the use of an additive and paving with the recycled mix.
In addition to using innovative techniques with the pavement, the team tracked the performance of the pavement itself. Diefenderfer explained his team wanted to be able to understand how the pavement section would perform during its life, so recording devices were embedded log the pressure, strain, temperature and moisture content.
Diefenderfer said installation was difficult because the team was operating in an active construction zone and the gauges used to measure asphalt strain are delicate. One challenge was ensuring the gauges stayed in place during paving and didn’t get damaged, so the team members encased the wires in flexible metal conduits to protect them.
“We can monitor performance during service life,” Diefenderfer said. “This has really been a unique opportunity.”
Last summer, Diefenderfer said his team installed a similar set of gauges in the area associated with the third segment of the I-64 project to monitor that stretch as well. He noted the segments are administered differently, and did not comment on the pavement techniques employed in the third segment.
“I-64 serves as the major corridor,” Diefenderfer said. “It’s a huge impact. The reason widening work was done [was] because this is a major bottleneck area. I’m sure predictability in their travel time will be very important to [truckers].”
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