By: Tara VanTimmeren
The Nevada Department of Transportation’s I-80, Elko County project has received recognition for achieving its goal of maximizing results while minimizing costs.
The project received the Asphalt Recycling & Reclaiming Association/Roads & Bridges Recycling Award for its cold in-place strategy, which began in July 2007 and will be completed in September 2008.
Sohila Bemanian of Optimum Pavement LLC said that, like any project, effort was made to optimize the results by spending the least amount of money and maximizing the value of the money that was spent.
Twenty miles of I-80 at Pequop Summit was experiencing some cracking, and cold in-place recycling (CIR) was chosen as the best solution. Road & Highway Builders served as the prime contractor, accompanied by Valentine Surfacing as the CIR contractor.
Typically, a minimum overlay is placed on the interstate system every eight years to maintain the pavement at the highest level of serviceability, Bemanian said. She said that the I-80 project should have a 20-year design life expectancy.
“Cold in-place recycling is a very effective way of retarding the reflective cracking,” Bemanian said. “After you do the cold in-place recycling, you place a minimum thickness of hot-mix asphalt on top of it, so a combination of recycling and minimizing the depth of the overlay allowed us to significantly cut the cost of the project.”
Other options were considered, but they were determined to produce the same results for a much greater cost. Full-depth reclamation, for example, would have cost about $8 million more and yielded the same life expectancy, Bemanian said.
The project began with recycling the pavement with Valentine Surfacing’s CIR train to a depth of about 3½ in. Other equipment used included the CMI PR-1000 Rotomil, a Caterpillar asphalt roller and an Ingersoll Rand asphalt paver.
“We removed the existing pavement that was cracked up, reprocessed it and placed it right back in, so there was no new material involved,” Bemanian said. “So you basically take the material, process, add some emulsion to it and put it right back in—and it makes it look like a brand-new pavement.
“After that process is done, obviously it will not be able to withstand interstate traffic, so you come back and cap that 3½ in. of recycling by placing 4 in. of hot mix on top.”
There were multiple challenges involved with the project, Bemanian said. The interstate traffic on I-80 proved to be difficult, regarding traffic control, length of closure and cure time prior to the hot-mix asphalt overlay. “You have a limit of where you can be recycling or closing lanes at one time. So all of that really adds up—you want to minimize downtime for your construction crew and maximize use of the equipment, but then you’re restricted by how many miles you can recycle before you need to stop and let it cure before the second crew comes and places the hot-mix overlay on top. All of that is almost like a jigsaw puzzle, where all the pieces match and come together.”
Pequop Summit in the middle of the project was another challenge. Steep grades to pull the CIR train up were required, which is “not impossible, but adds more to what the contractor needs to do because it is very steep, and 3½ in. is a lot of material that you’re building up to move,” Bemanian said.
The speed of traffic on downhill areas was another challenge, Bemanian said. “The trucks coming downhill are going pretty fast, so you really do not want to be out there in the vicinity. You need to be very careful about it.”
“In addition to the roadway work, there was some pipe work and other nonpavement-related issues,” Bemanian said. A significant amount of pipe crossings to build in the middle of the job presented issues with where the CIR work could be performed. Basically, work had to be done on either end of the project while the pipe crossings were being done in the middle. “The pipes had to be placed before they can place the CIR, which means there’s going to be concurrent work going on, and you have to get the coordination to take place to make it all happen.
“It’s like any job—it had its unique challenges. And then also we had a lot of restrictions—you have to recycle it, you have to let it cure before you place the overlay on it, and you don’t really want to have traffic on it. So all of that comes to a challenging part of the construction process.”
The solutions to the challenges made for an award-winning project that was not only cost-effective, but also adhered to sustainability—a principle Bemanian feels is underrated when it comes to highway construction.
“Sustainability has become a huge issue that everyone is talking about—trying to minimize waste and utilize existing resources,” she said. “I think when it comes to highway construction, we’re kind of backward in that respect. We’re not taking advantage of existing material that we have already in our infrastructure, and recycling allows us to do that.”
Producing 3½ in. of new crushed aggregate and new materials would require a lot of energy, Bemanian said, and recycling, ton-per-ton, requires 80% less energy than hot mix alone.
“The process really, truly allows us not only to be cost-effective and expect a long performance from the pavement, but to meet sustainability requirements, and that’s something I really emphasize,” Bemanian said. “Every corporation has the responsibility to meet the triple bottom line, which is social, environmental and economic aspects of a job. Recycling truly does meet all those criteria.”
