Hitting the Road for High-RAP

Advancing high-RAP through training and real-world results

Did you know a 30,000-ton reclaimed asphalt pavement (RAP) stockpile is worth the virgin materials it saves? That stockpile will replace over 28,000 tons of clean aggregate. The reincorporated RAP binder is equivalent to seventy 6,000-gallon binder transport trailers.

The National Asphalt Pavement Association's (NAPA) 2023 industry survey reports an average RAP usage of 22% across multiple State Department of Transportation (DOTs), agencies, and commercial markets. Over the past two decades, there has been a slow but steady increase in the allowable RAP in DOT specifications, with 34 State DOTs having allowable RAP beyond 20% (Figure 1).

To help agencies move beyond the status quo, the Federal Highway Administration’s (FHWA) AIEI Program (Asphalt | Innovate | Enlighten | Implement) recently took its high-RAP mixture strategies workshop on the road.

Managed by the University of Nevada-Reno (UNR), the AIEI program brings technical expertise directly to State DOTs. UNR’s Adam Hand, along with NCAT’s Tom Harman and Fan Yin, delivered an intensive, one-day technical training workshop to Montana and North Dakota DOTs.

To support continued progress, agencies are seeking practical strategies to increase RAP use.

Figure 1. Allowable RAP Increasing in DOT Specifications (Source: NAPA)

Moving beyond a lecture

The workshop was designed to be interactive, moving away from standard slides to real-time participant engagement through live polls and "Pavement Trivia."
Some of the questions that sparked discussion among participants included:

• "At what level is RAP-fractionation recommended?"
Participants explored how this practice is essential for managing the variability of high-RAP mixes.

• "True or False: The use of Recycling Agents (RA) with Warm-Mix technologies ensures High-RAP performance."
The “False” answer showed these tools must be validated through Balanced Mix Design to ensure long-term performance.

RAP-fractionation (Source: Adam Hand UNR)

Proving performance

The workshop also focused on state DOT success stories. One compelling segment focused on "virtual site visits" to states that have embraced high-RAP as a standard, resource-responsible practice.

"Since implementing High-RAP specifications in 2013, we have averaged 39% RAP usage, with ranges typically between 35% and 50%. Remarkably, our Nebraska Serviceability Index (NSI) has actually increased during this period, with 92% of their interstate system currently rated as 'Good.' Beyond performance, the economic impact is awesome: in fiscal year 2023 alone, our use of RAP provided an estimated value of nearly $89 million."    
– Nebraska DOT

State highlights:

• Florida DOT: Allows unlimited RAP use for some type mixes. Several producers successfully use 40% RAP.

• New Jersey DOT: Employs a BMD approach to achieve 20% minimum RAP in surface mixtures and 30% in base courses, ensuring durability through performance testing rather than just recipe-based specs.

• Wisconsin DOT: Reported that over 95% of their 2.8 million tons of asphalt mix contains RAP, reaching 40% in some mixtures.

The workshop concluded with a clear takeaway: High-RAP mixes are not just an "experimental" alternative but a proven strategy for high-traffic loading when supported by tools like BMD, along with grade bumping and recycling agents.

By monitoring pavement performance and working closely with producers, the AIEI program is helping more states join the ranks of those who are resource-responsible without compromising on quality or ride.

Contact Tom Harman for more information about this research.