Empire State Performance

By Bruce Barkevich, Contributing Author

Over the past decade, highway agencies across the United States have increasingly embraced balanced mix design (BMD) as a methodology to improve pavement performance and optimize material use. 

Among the states leading this transition is the New York State Department of Transportation (NYSDOT), which has worked to integrate performance testing into its mixture design practices. This effort began in 2019 and continues to develop into a robust mix qualifier.   

A major part of New York’s approach has been its emphasis on the High-Temperature Indirect Tensile Strength Test (HT-IDT) for rutting and permanent deformation evaluation. The state has combined with cracking tests such as the Indirect Tensile Cracking Test (IDEAL-CT). 

New York’s experience demonstrates how performance tests can be selected, refined and implemented gradually to yield more reliable pavement outcomes. It all started with data and benchmarking New York’s existing mixes. 

As agencies nationwide push for longer-lasting, more sustainable pavements under increasing budget and environmental pressures, New York’s transition to performance-engineered mixtures offers a real-world blueprint for the future of asphalt mix design. By moving beyond traditional volumetrics and embedding practical, lab-verified performance tests into everyday specifications, NYSDOT is demonstrating how balanced mix design can accelerate innovation, enable higher recycled content, reduce risk for agencies and contractors and deliver measurable value to taxpayers. 

Performance testing is no longer just a research concept—but a scalable, implementable tool shaping the next generation of asphalt mixtures across the industry.
 
For decades, NYSDOT, like most agencies, relied on volumetric mix design to evaluate asphalt mixtures. While effective as a quality baseline, volumetrics did not predict long term mixture performance in the field. Performance engineered mixtures, or PEM as it is referred to in New York State (NYS), has become the best approach to determining mix quality on a very real-time basis. 

New York strives to find ways to make its products more sustainable and more durable. 

In fact, as the state continues down the path of sustainability, the Life Cycle Assessment (LCA) of a pavement will determine the overall Global Warming Potential (GWP) of asphalt mixtures. So, to be able to test mixes for performance will help the industry innovate by introducing sustainable products such as:

• Recycled Asphalt Pavement (RAP)
• Recycled Asphalt Shingles (RAS)
• Polymer-modified and specialty binders
• Additives and rejuvenators

And many more to come. Volumetrics wouldn’t capture the mix performance as these new variables are introduced. That is where performance testing comes in.  

In the past, specialty mixes would be placed on the roadway, and an agency would track its performance for multiple years to determine its success. Or, a mixture would be sent to a research center, where mix quality would be determined. These tools were effective, but time consuming. Changes came at a glacial pace.  

Following national trends in the asphalt industry, leadership in NYSDOT’s Material Bureau determined this was the next “big” thing. Data has been collected, research established and the tools are starting to be narrowed down.  

NYSDOT evaluated numerous performance tests over the past decade. The goal was to find reliable, repeatable and practical test methods to quantify rutting resistance and cracking tolerance.  

Ultimately, New York centered its efforts on two repeatable, but also timely, tests that an asphalt producer could perform in their own lab, the results to which a state DOT could verify in its regional lab.  

• High-Temperature Indirect Tensile Strength (HT-IDT) for rutting / permanent deformation evaluation
• IDEAL-CT for intermediate-temperature cracking evaluation

The HT-IDT test is performed at elevated temperatures and loads a cylindrical specimen in indirect tension. The resulting tensile strength and deformation behavior are indicators of a mixture’s susceptibility to permanent deformation. This test met all the criteria needed to become a benchmark test:

• Practicality for Contractor and DOT Labs (equipment investment wasn’t extreme)
• Repeatability and Reliability  
• Sensitivity to Mix Variables  
• Delivered timely results  

The IDEAL-CT emerged as the best cracking test for New York and for many states pursuing BMD tests.  

• No sawing or cutting is required, pucks can be fabricated in a standard gyratory compactor
• Repeatable and reliable (as well)
• It will qualify mixes in cracking modes.

Pilot projects allowed producers to evaluate their mixes using HT-IDT and IDEAL-CT. Common adjustments included changes in binder content, RAP percentages, binder grade and rejuvenator use.  

It also allowed producers and DOTs to become familiar with the test method. They also became proficient in sample prep and final sample testing. The pilot phase has been in effect, really, since the beginning.  

NYSDOT began inserting special notes into projects in 2019. To date, hundreds of jobs have been performed utilizing the Performance Testing criteria.  

As was the case across the U.S., the original Superpave mixtures were rut resistant but tended to crack. New York made major mix adjustments to allow for lower mix design gyrations and adjusting design air voids from 4% to 3.5%.  

These changes took place between 2006 and 2009. These changes allow producers to get additional liquid asphalt into the mixes. This added liquid restored the mixes’ crack resistance along with continuing to hinder rutting.  

These mix changes, which are still used today, have been the basis for improved mixture quality. NYSDOT also moved to 100% polymer modified liquid asphalt. Along with high quality aggregates, these liquids also enhance mix quality, which is proven by the CT and HT test results.  

Beginning this year, NYSDOT will be move to their “PEM” specification for ssphalt mixtures as a standard spec. This means every project bid will have a performance criteria to it.  

New York’s testing to this point will be an indication of mix quality. Whether or not it quantifies the expected increase of life is yet to be determined. But as data is collected and projects are placed, the added requirement of performance testing is expected to prove that NYSDOT and the taxpayers of the state are getting a high-quality mix.  

In addition to the aggressive asphalt mix changes in New York, there has been a shift to warm mix asphalt (WMA). In 2021, NYSDOT implemented its own version of WMA.  

For years, New York has allowed producers to supply warm mix as it fit their production. Since 2021, NYSDOT has required mix to be delivered to the paver at 295 degrees utilizing an approved WMA technology.  

It is believed that this mix specification is showing a 20-degree reduction in mix temperature. Across millions of tons supplied to state agencies, that is a substantial reduction in greenhouse gas emissions.  

As has been the case for years, NYSDOT and the asphalt industry have partnered to see this positive and progressive change to the products that are used. These efforts will continue because of the long and trusted relationship that was established years ago.  

Bruce Barkevich is the vice president of the New York Construction Materials Association.