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Publication Number:  FHWA-HRT-08-004    Date:  Nov/Dec 2008
Publication Number: FHWA-HRT-08-004
Issue No: Vol. 72 No. 3
Date: Nov/Dec 2008


The National Highway Institute (NHI)

by Stacy Stottmeister

NHI Promotes In-Place Asphalt Recycling

According to the Asphalt Recycling & Reclaiming Association (ARRA), asphalt is the most recycled product in the world. In fact, more asphalt is recycled annually than all other wastes combined.

ARRA defines in-place recycling as an onsite method of recycling that rehabilitates and preserves deteriorated bituminous pavements and thereby reduces the use of new materials. Jason Harrington, a recycling technology engineer at the Federal Highway Administration (FHWA), compares the in-place recycling process to a farmer tilling the soil every year. In his analogy, a farmer adds nutrients and prepares the soil every spring, and when it comes time to plant, the soil is viable and ready for crops. "Imagine how much more effort would be needed if the farmer had to bring in completely new soil every year at planting time," Harrington says. "Similarly, by using in-place recycling technologies, we reduce the need to bring in new supplies of paving materials and extend the supply of nonrenewable resources."

However, despite asphalt's recyclability, in-place recycling technology is underutilized by departments of transportation (DOTs), perhaps because it is "a newer kid on the block," Harrington says. "But with proper training and technical information provided by FHWA and ARRA, the extent of use could easily double and still have plenty of room for growth."

Benefits of In-Place Recycling

In-place recycling can reuse all the old pavement back into the highway. The hot-mix asphalt (HMA) plant recycling process can reuse 25 to 35 percent of the old, reclaimed asphalt pavement effectively, by blending it back in with new HMA for a highway project. Overall, about 80 percent of all asphalt materials removed are reused in some type of highway application.

In addition to preserving aggregate resources, other benefits of in-place recycling are the lower cost of construction, reduced fuel use, and lower greenhouse gas emissions. Further, Harrington says, reports from States are showing lower costs for long-term maintenance and improved ride quality over the lifetime of the pavement compared with the conventional mill-and-fill process.

"With the rising costs of asphalt and fuel, the dollar savings for in-place recycling, when compared with the cost for various other rehabilitation options, will really surprise a program manager working with a tight budget," Harrington says. In fact, the cost for in-place recycling can be about 30 percent less then milling and hauling off 5 to 10 centimeters (2 to 4 inches) of pavement and then bringing new HMA pavement (containing at least 20 percent reclaimed asphalt pavement) back onsite. The cost of hauling materials to and from the jobsite greatly increases the overall cost.

In-place recycling also can slow roadway deterioration, facilitate preserving and upgrading a higher proportion of pavements, and avoid costly reconstruction. By reusing existing materials, this cost-effective strategy enables public works officials to spread available funds over a much greater area.

NHI's Asphalt Recycling Course

To fill a gap in the traditional education for transportation professionals involved in pavement rehabilitation and preservation, FHWA and the National Highway Institute (NHI) developed the course Asphalt Pavement Recycling Technologies (FHWA-NHI-131050). Created in partnership with ARRA and the National Center for Asphalt Technology, the course provides indepth technical knowledge on several recycling methods. Specifically, the training covers performance of recycled mixes, specification guidance, selection criteria for various types of pavement recycling strategies, economics of recycling, and structural design of recycled pavements.

The course targets State DOTs and local highway officials and administrators. Pavement design engineers and technicians, and construction engineers and inspectors, involved in recycling asphalt pavements also could benefit from the training.

Upon completing the session, participants should be able to describe the various methods of recycling pavements, determine when asphalt recycling is a viable rehabilitation alternative, and select the most appropriate asphalt recycling method or technique. In addition, participants will learn to identify materials and mix designs for recycled pavements; specify equipment, construction methods, and quality control and quality assurance steps involved in asphalt recycling; and demonstrate design methods for hot and cold recycled pavements.

Planned updates to the course include discussion of new technologies and addition of case studies and specification guidance that address economic savings and life-cycle cost performance of asphalt recycling.

Workers demonstrate cold in-place recycling on a highway project in New York State. FHWA engineers visited the jobsite during a national review of the in-place recycling process.
Workers demonstrate cold in-place recycling on a highway project in New York State. FHWA engineers visited the jobsite during a national review of the in-place recycling process.

In-Place Recycling Conference

To help spread the word about the benefits and applications of in-place asphalt recycling, FHWA and ARRA hosted a conference in Salt lake City, UT, in June 2008. The First Western States Regional In-Place Recycling Conference drew pavement professionals from FHWA, State and local DOTs, metropolitan planning organizations, academia, contractors, and suppliers. The event provided a forum to showcase the latest in research, design, specifications, materials, and construction practices, and to promote the cost benefits of in-place recycling.

The conference included a site visit to an in-place recycling project in Nevada, a State with extensive experience with asphalt recycling. The Nevada Department of Transportation recycled more than 1,100 kilometers (700 miles) of pavement from between 1997 and 2005. The site, located on I-80, consists of 32 kilometers (20 miles) of in-place recycling and earned a 2007 Recycling Award from Roads & Bridges magazine. The field trip provided the opportunity for attendees to see a cost-effective application of in-place recycling firsthand. More information is available at www.pavementpreservation.org/recyclingworkshop.

To schedule a session of NHI's Asphalt Pavement Recycling Technologies (FHWA-NHI-131050), contact the NHI Scheduler at nhitraining@dot.gov. To learn more about NHI courses, visit www.nhi.fhwa.dot.gov.

Stacy Stottmeister is a contractor for NHI.



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