Recycling pavement for a sustainable future

To meet increasing needs for more sustainable pavement practices while continuing to improve its long-term performance, IDOT is teaming up with the Illinois Center for Transportation to solve the puzzle.

The joint project, “R27-196-HS: Rheology-Chemical Based Procedure to Evaluate Additives/Modifiers Used in Asphalt Binders for Performance Enhancements: Phase 2,” will investigate methods to soften asphalt binder to reduce cracking. As recycled materials are added to hot mix asphalt, the asphalt tends to harden and become brittle, potentially leading to premature cracking.

“Asphalt binder keeps the aggregate together in the pavement just like corn syrup or sugar keeps the granola together in granola bars,” said B.K. Sharma, senior research engineer at Prairie Research Institute’s Illinois Sustainable Technology Center. “It’s a gluing material that keeps the aggregate together for a very long period of time.”

Researchers added different modifiers or softening additives to asphalt binders to improve long-term pavement performance. After examining the mechanical and chemical properties of the modified binders, the research team proposed testing protocol and thresholds for different performance indicators to ensure desired pavement performance and validated them with field samples.

“The protocol and thresholds suggested from this work are unique and ones that have been highly sought after nationally,” said Kelly Morse, IDOT chief chemist, who is leading the effort with Sharma. “The ability to implement a protocol to vet the performance of modified binders’ rheological and chemical properties in both the un-aged and aged condition will provide a significant contribution to the state practice for asphalt binder testing and qualification.”

IDOT is one of only a handful of transportation agencies in the U.S. with chemists that extensively test asphalt binders. Next steps include initiating testing in IDOT’s Central Bureau of Materials Bituminous Chemistry lab and working with the research team to ensure ease of method reproduction from one lab to another to facilitate the implementation of the newly developed protocols. Drivers in Illinois can expect better ride quality and fewer disruptions from maintenance and repair activities because of the joint effort.