Cold Recycling Finally Has a Construction Guide Specification!

For years, readers of this newsletter have found interesting information and updates on Cold Recycling (CR) processes, such as Cold Central Plant Recycling (CCPR) and Cold In-place Recycling (CIR). With all the talk of great performance even on high-traffic volume roads (and the famed NCAT Test Track) there has been a deluge of State Departments of Transportation (DOTs) personnel, Federal Agencies, and even industry members looking to NCAT experts to provide insight into how to craft a specification to deliver a high-quality, reliable CR pavement. This has been especially important considering NAPA’s The Road Forward plan, the industry’s drive to net-zero emissions, and U.S. DOT grant opportunities (such as FHWA’s Climate Challenge projects), which focuses on lowering greenhouse gas (GHG) emissions and energy associated with producing and constructing pavements. 

In 2020, a team from NCAT led by Principal Investigator (PI) Dr. Benjamin Bowers, PE (that’s me!) was awarded National Cooperative Highway Research Program (NCHRP) Project 14-43, Construction Guide Specifications for Cold Central Plant Recycling and Cold In-Place Recycling. Team members included Co-PI Dr. Brian Diefenderfer, P.E. at the Virginia Transportation Research Council (VTRC), Auburn/NCAT alumnus, Asphalt Recycling and Reclaiming Association (ARRA) technical director Dr. Stephen A. Cross of S. Cross & Associates, LLC, NCAT Associate Research Professor Dr. Adriana Vargas, and former Assistant Research Professor Dr. Fan Gu, PE. The objectives of this research project are to: 

1. develop and produce a proposed AASHTO Construction Guide Specification, and 
2. develop a Best Practices Guide and training materials for the construction of CIR and CCPR. 

You might ask: how do you go about putting together an AASHTO Construction Guide Specification? The first step was to assemble the right team: Our team consists of implementation-minded academics (Bowers, Vargas, Gu), agency representation (Diefenderfer), and industry representation (Cross) – the latter two who just happen to also be implementation-minded academics. Then, we gained insights from our NCHRP panel, findings from the literature review, and from feedback to a survey that went out to DOTs, counties, and municipalities. The information from these sources helped us gain an understanding of what was working and what wasn’t in their CR specifications. Independent interviews were also conducted with DOT personnel identified in the survey, as well as experienced contractors who could speak to the construction process. This was critical because the team wanted to make a flexible specification that would suit the needs of the agency, as well as see these techniques grow in use, while not discouraging bids and competition due to a limiting specification. 

The team then set out to draft the first specification. All five key elements of an AASHTO Construction Guide Specification were outlined and approved by the panel. Using experience from the team, input from DOT and industry experts, and drawing on some of the “top” specifications, the team drafted a CR specification. This iterative process included multiple panel reviews and a round of reviews from the team’s Industry Technical Support Team – a team of industry experts who could provide insight into the challenges induced by the proposed specification language – we finally had a final draft. The draft specification was then submitted to AASHTO to begin committee reviews. 

The final report contains a Best Practice Guide and training materials that will be useful for agencies and contractors interested in using CR. These guides will draw attention to many common questions, concerns, and will help troubleshoot challenges in the field. These guides are also an excellent complement to the commentary provided in the draft AASHTO specification. The training materials, in the form of a PowerPoint file, are intended to be complimentary materials that can be used in preparation for a project or for Just in Time Training right before construction commences. 

Publication of the final report is forthcoming, and the draft AASHTO Guide Specifications are in review. Keep an eye on TR News and NCAT social media for announcements of final publication, or simply search “NCHRP 14-43” in your favorite web search engine.  

Contact Ben Bowers for more information about this research.