Largest Pavement Testing Facilities Forge Historic Hot and Cold Climate Research Partnership

The worlds two largest full-scale accelerated pavement testing facilities have joined forces in a landmark partnership that promises to transform how state departments of transportation and municipalities approach pavement design across vastly different climate zones. The National Center for Asphalt Technology (NCAT) based in Alabama and the Minnesota Road Research Facility (MnROAD) are now sharing resources, expertise, and experimental protocols under a formalized agreement that allows them to test identical pavement materials and designs under both extreme heat and extreme cold conditions. For professionals seeking deeper knowledge of pavement engineering fundamentals, this partnership builds on decades of research covered in Asphalt Pavement Engineering Mix Design Construction Methods Rehabilitation, which provides essential context on how laboratory findings translate to field performance across different climate regions.

This collaboration addresses a longstanding concern among transportation officials in northern states who questioned whether research findings from warm-climate testing facilities applied directly to their colder environments. By running parallel experiments at both locations, the partnership now produces findings that are implementable in both warm and cold climates, giving state DOTs and local agencies a more reliable evidence base for their pavement investment decisions.

The Two Premier Accelerated Pavement Testing Facilities

Each facility brings unique capabilities and infrastructure to the partnership. Understanding their individual strengths explains why the combined research program is greater than the sum of its parts.

NCAT Pavement Test Track in Alabama

The National Center for Asphalt Technology, headquartered at Auburn University, operates a 1.7-mile oval test track in Opelika, Alabama. This track comprises 46 individual test sections, each 200 feet in length, sponsored in three-year cycles by state DOTs, the Federal Highway Administration (FHWA), and industry partners. Each sponsor brings specific research objectives for their sections alongside shared objectives that benefit the entire track program. The facility subjects test sections to two years of continuous trafficking by 70-ton tractor trailers, simulating up to 15 years of interstate highway traffic in a compressed timeframe.

MnROAD Facility in Minnesota

Owned and operated by the Minnesota Department of Transportation, the MnROAD facility is located approximately 40 miles northwest of Minneapolis. Its infrastructure includes three distinct roadway elements:

• A 3.5-mile section of Interstate 94 for high-volume traffic testing
• A 3.5-mile bypass roadway for diverting interstate traffic when test sections need to be accessed
• A controlled access 2.5-mile closed-loop low-volume roadway that simulates rural road conditions

MnROAD features 50 test cells, each 400 feet in length, sponsored by state DOTs, the Minnesota Local Road Research Board, FHWA, and industry. Principal research staff includes Ben Worel, Dave Van Deusen, and Chelsea Hanson, supported by MnDOT Materials Research personnel Jerry Geib, Paul Nolan, and Jeff Bruner.

Climatic Contrast Between Facilities

The climatic differences between the two locations are extreme and deliberate. Minnesota winters bring heavy snowfall, with up to 170 inches of snow annually and temperatures plunging as low as -60 degrees Fahrenheit. Alabama, by contrast, experiences mild winters and very warm to hot summers, with the highest recorded temperature reaching 112 degrees Fahrenheit in Centreville. This natural temperature differential is the very variable the partnership exploits to generate climate-comprehensive pavement performance data.

Parallel Experiments Under a Formal Partnership

Researchers from NCAT and MnROAD have collaborated informally for years through the Transportation Research Board’s Committee on Full-Scale Accelerated Pavement Testing. However, research programs at both facilities were historically limited to state DOTs operating in similar climates. The new formal agreement changes this dynamic entirely.

According to Dr. R. Buzz Powell, PE, Assistant Director and Test Track Manager of NCAT, the partnership now covers parallel experiments under an exceptionally broad range of climatic conditions, with funding provided by nineteen state DOTs through the national Transportation Pooled Fund that supports the NCAT Pavement Test Track. Dr. Powell traveled to the MnROAD facility in August 2016 to oversee construction of the first parallel test sections. Crucially, the same contractor that built the NCAT sections, East Alabama Paving, constructed the test cells at MnROAD to ensure treatments at both facilities were built identically.

Two Core Research Focus Areas

The current MnROAD-NCAT group experiments concentrate on two critical areas:

1. Validation of cracking tests to identify laboratory methods that accurately predict field cracking performance
2. Effectiveness of pavement preservation treatments measuring how different surface treatments extend service life under varying traffic and climate conditions

Predicting Pavement Cracking Across Climate Zones

Cracking in asphalt pavements is widely recognized as a principal indicator of pavement failure caused by fatigue from repeated loading. It often appears as alligator-type cracking in wheel paths. Understanding the mechanisms behind different crack types is essential for developing reliable laboratory test methods.

Three Crack Types Under Study

• Near-surface fatigue cracking initiates at or near the pavement surface and propagates downward. It is more prevalent in hot climates where higher temperatures soften the asphalt binder, making the surface layer more susceptible to traffic-induced shear stresses.
• Low-temperature cracking occurs when thermal contraction stresses exceed the tensile strength of the asphalt mix. This is the dominant mechanism in cold climates where extreme temperature drops cause the pavement to contract and fracture.
• Reflective cracking commonly occurs in rehabilitated pavements near the junction with an underlying cracked asphalt layer. Cracks propagate upward to the surface of the overlay, regardless of climate.

Hot weather sections were built at the NCAT track to study near-surface fatigue cracking, while cold weather cells at MnROAD focus on low-temperature cracking. At both facilities, mixes incorporate various combinations of recycled asphalt pavement (RAP) and recycled asphalt shingles (RAS), providing a broad range of cracking performance for study. An array of laboratory tests is being run on both lab-produced and plant-produced mixes to identify those that most accurately predict field performance.

Pavement Preservation Trials and Practical Applications

The preservation group experiments measure the effectiveness of various treatments in improving pavement condition and extending service life for both low-traffic and high-traffic roadways. Test sections were built on local roadways near both facilities to ensure realistic traffic and environmental exposure.

Treatment Locations by Region and Traffic Level

• Southern low-traffic: Lee County Road 159 near the NCAT main office in Auburn, Alabama
• Southern high-traffic: US-280 near the NCAT Pavement Test Track in Opelika, Alabama
• Northern low-traffic: County Road 8 in Pease, Minnesota
• Northern high-traffic: US-169 in Pease, Minnesota

Preservation Treatments and Their Benefits

Treatments installed across the test cells included chip seals, microsurfacing, scrub seals, cape seals, and thin overlays. All are recognized by the Federal Highway Administration as effective methods for preserving pavements that remain in good condition before the onset of serious structural damage. The FHWA notes that applying such cost-effective treatments at the right time restores pavements almost to their original condition, postponing costly rehabilitation and reconstruction.

For a deeper look at pavement preservation chemistry, explore Refined Tar Based Pavement Sealers What Pavement Professionals, which examines the regulatory landscape surrounding pavement sealer chemistries.

RAP-RAS Mix with Asphalt Rejuvenator

One of the most significant experiments involved a three-quarter-inch wearing course inlay of dense graded hot mix asphalt containing RAP and RAS dosed with an asphalt rejuvenator. This addresses a critical industry concern: as fewer new roads are built and the call for reusing milled materials grows, the DOT community worries that recycled materials may cause premature cracking due to their brittle, oxidized condition. The manufacturing cost savings of incorporating RAP and RAS to replace virgin aggregates and binder are attractive, but the impact on pavement performance must be thoroughly understood.

The team used Delta S, a plant-based liquid chemistry from Collaborative Aggregates LLC, piped in line with the liquid asphalt supply during production. The treatment was applied on US Route 169 after milling three-quarter inches of existing wearing course. The paving train included a ROADTEC SB-2500 material transfer buggy feeding a ROADTEC Spray Paver. Compaction was performed by a SAKI SW770 HF roller in vibrator mode with a SAKI SW654 static roller completing finish compaction, achieving a nuclear density reading of 94 percent. Equipment and materials were donated by Dillman Equipment, SAKI, and Collaborative Aggregates.

Professionals interested in maximizing returns on pavement maintenance investments can review Maximizing Value At Pavement Maintenance Trade Shows Lessons for guidance on staying current with emerging preservation technologies.

Data Collection and Industry Impact

Field performance of both experiment groups is monitored with similar automated technologies at both locations, and data is stored in a common database. This parallel design produces findings implementable by a larger base of state DOTs that previously may have had concerns about climate applicability. Thousands of cash-strapped cities and towns that rely on state DOT specifications for local roads also benefit from improved pavement designs validated across climate extremes. For those involved in pavement rehabilitation operations, the equipment technologies used in these experiments are covered in Tearing Up the Pavement Modern Cold Milling and, discussing machinery and methods for preparing pavement surfaces.

Key Takeaways for Pavement Professionals

1. Climate-validated designs tested under both extreme heat and extreme cold give DOTs confidence that specifications perform in their specific climate zone
2. Reliable cracking tests emerging from this validation work will enable better mix design decisions before construction begins
3. Timely preservation restores pavements nearly to original condition at a fraction of rehabilitation costs
4. Sustainable materials guidance from rejuvenator experiments allows safe increases in RAP and RAS content without sacrificing durability
5. Modern equipment integration demonstrates how material transfer vehicles and advanced compaction technology achieve quality outcomes

The formalized NCAT-MnROAD partnership represents a milestone in pavement engineering research. By combining the resources, expertise, and climatic diversity of the worlds two largest accelerated pavement testing facilities, this collaboration generates the comprehensive, climate-independent data the transportation community has needed for decades. State DOTs, municipal engineers, and pavement professionals who follow these findings will be better equipped to build roads that last longer, cost less to maintain, and perform reliably whether laid in the heat of Alabama or the deep freeze of Minnesota.