High RAP Pavement Survey: A Carbon Reduction Success Story
In 2020, Mercer Road in Lexington, KY served as a trial for a newly developed method for increasing recycled asphalt pavement (RAP) content in asphalt mixes. BATT performed the BMD mix design and follows up annually to check the pavement condition.
Background: Mercer Road
Mercer Road serves as the feeder route to the Lexington/Bluegrass Airport and sees plenty of daily, heavy-load traffic from warehouses serving UPS, FedEx, Amazon, and other industrial companies. The Lexington-Fayette Urban County Government (LFUCG) was searching for pavement solutions that would provide improved sustainability by increasing the amount of RAP in the mix without giving up service life. This project was a challenged due to the high RAP mix and high truck loads. It demanded close attention to detail.
ATS Construction placed a 250-ton trial using 45% RAP with PG 64-22 at 5.7% total binder in a mix that utilized (8.4 oz mix ton) of Surface Tech’s 38mm ACE XP polymer fiber along with TUFFTREK 4007 (4.2% of total asphalt content) engineered bio-oil from Bakelite. The total binder replacement wa 47.5%. The aramid fiber replaced the typical PG 76-22 binder used in the 15% RAP control section to ensure rutting control in the high RAP mix and reduce cracking.
How this and all the projects reduced carbon compared to a traditional pavement
Designed utilizing RAP, additives, and bio-oil.
A BMD-designed mix was focused on end-result performance for a longer pavement life, thus reducing the construction cycle.
Reduced carbon by using less mined aggregates and transport of new aggregates.
Reduced the need for new asphalt binder.
Conclusion
After nearly four years, while the control lane and the high-RAP lanes are similar, the high-RAP lane is showing slightly better performance, generating a pavement condition index of 96 versus 89 for the control, derived from our BATT Vision technology. The Mercer project was intentionally and purposefully designed to solve the age-old problem of premature cracking that can occur in RAP mixes (especially high RAP over 20%), while also increasing the amount of RAP content from a typical 15% up to 45%. Bio-oils not only softened the virgin binder (e.g., PGxx-22 to PGxx-34), but also replaced lighter components of asphalt binder and stabilized the asphaltene structure to restore the oxidized RAP binder. The para-aramid polymer fibers provided reinforcement to improve both rutting and cracking resistance in the final mixture.
For more information on how BATT can help you increase RAP content and decrease rutting and cracking, visit our website.
