Selecting the right asphalt binder for airfield pavements has long been a challenge for design engineers.
Unlike highways, airfields must withstand heavier aircraft loads, slow or stationary runway and taxiway movement and strict Federal Aviation Administration (FAA) and Department of Defense (DOD) specifications. Choosing the wrong binder can cause pavement to resist one type of damage but fail prematurely from another or drive-up costs if the binder is difficult to source.
To address these challenges, the Airport Asphalt Pavement Technology Program (AAPTP), in partnership with FAA and the National Asphalt Pavement Association (NAPA), sponsored binder selection research, led by the National Center for Asphalt Technology (NCAT).
The project's goal was to transform complex and sometimes inconsistent binder requirements into a standardized process and tool — saving engineers time, reducing errors and improving pavement performance.
"Although the engineering notes in FAA and DOD specifications are very useful, they can also be limited," said Raquel Moraes, NCAT principal investigator. "Selecting the correct asphalt binder grade still requires significant background knowledge from the design engineer, such as accounting for aircraft gross weight in FAA specifications or tire pressure in DOD projects."
NCAT researchers surveyed all 50 state highway agencies, Puerto Rico and several Canadian provinces to document which binder grades were commonly specified and available in each region. This database was then cross-checked with Asphalt Institute specifications to ensure accuracy.
The team also reviewed FAA and DOD specifications, including FAA P-401, P-403 and P-404, as well as Unified Facilities Guide Specifications for airfield paving. The team mapped when and how binder grade "bumps" are required based on aircraft gross weight, tire pressure, pavement location, reclaimed asphalt pavement content and climate conditions.
The team then created step-by-step flowcharts that mapped the engineering decisions used when applying FAA and DOD standards. They compiled their findings into a final report, titled "Guidance for Selection of Proper Asphalt Binder Grade," and then took the next step of turning the guidance into a practical tool.
"We wanted to capture all of the information in the guidance and make it available through an easy-to-use interface that helps avoid the standard errors that occur when interpreting specifications," said Ben Ciavola, managing director of software and data pf WAP Sustainability Consulting.
The result is the Airfield Asphalt Binder Selection Tool, a free, web-based resource for pavement engineers. The tool guides users through selecting a base binder grade by state and county, applying grade adjustments for aircraft weight and movement and checking binder availability in the region. It also flags when additional requirements apply, such as polymer modification or elastic recovery testing.
In some cases, the recommended binder may not be part of the standard supply in that state or county. Rather than leaving users at a dead end, the tool directs them to the Association of Modified Asphalt Producers, which can connect engineers with suppliers able to provide specialty binders not typically specified but still required for certain projects. This ensures that even when a binder is difficult to source locally, engineers have a clear path to obtaining the right material for the job.
The tool, accessible on both desktop and mobile devices, generates clear, one-page reports that document every adjustment and can be shared with project teams. It gives engineers clear, research-based recommendations they can trust by embedding FAA and DOD requirements into an interactive platform.
"Keeping the database updated will be a priority so the tool remains a reliable resource even as binder availability and standards evolve," said Richard Willis, NAPA vice president of engineering, research and technology.
Future updates may also incorporate insights from ongoing studies, such as research into making airfield pavements more resilient to flooding and extreme weather.
The FAA has expressed support for the tool, viewing it as a practical way to bring greater consistency to binder selection across the aviation industry. While the agency will not mandate its use, the tool aligns closely with FAA specifications and gives engineers a reliable shortcut through what can otherwise be a complex and time-consuming process.
By making binder selection more transparent and accessible, the FAA and its partners hope to reduce errors in project submittals, save time in design reviews and improve communication between contractors, suppliers and engineers.
For more information, visit go.asphaltpavement.org/web-172.
