As part of the journey towards performance-based mix design (also referred to as Balanced Mix Design), VDOT and VAA members are piloting the use of high recycled asphalt pavement (RAP) content in asphalt mixtures. For purposes of this pilot, high RAP is defined as mixtures containing 40% or greater RAP. These higher RAP contents are typically accomplished in a number of ways. Methods include the use of “rejuvenators” to reactivate the aged RAP binder (in conjunction with a typical PG 64S-22 base binder) and the use of softer base binders such as a PG 58S-22 or PG 58S-28.
Superior Paving Corp. began the first high RAP pilot project of this paving season on Thursday, June 27 and utilized both of the referenced methods. The first effort utilized an SM-9.5A asphalt mixture with 40% RAP content and Ingevity’s Evoflex rejuvenator. The mixture was produced at their state of the art Bull Run plant in Chantilly, VA and was placed on Route 701 (Logmill Rd) in Prince William County. Approximately 1,500 tons were placed on June 27 and 28. Aside from the standard asphalt content, gradation, and volumetric testing, specific BMD testing protocol for this project included Ideal CT for cracking susceptibility, Cantabro for durability and APA for rutting.
Both Superior and VDOT/VTRC performed the referenced testing. Initial test results were favorable with both Ideal CT and Cantabro tests passing the preset targets. Superior’s initial test results indicate Ideal CT results ranging from 95 to 130 (minimum specification limit is 70) and Cantabro results ranging from 3.0 to 3.6 (maximum specification limit is 7.0). Additionally, the VTRC reported similar results with Ideal CT tests ranging from 101 to 136 and Cantabro tests ranging from 3.5 to 4.2. The VTRC also performed APA rut testing with results ranging from 5.3mm to 6.2mm. Danny Poole, Superior Paving’s Director of Quality Assurance, stated, “Based on early results with 40% RAP using a rejuvenator, we are very satisfied with the IDEAL CT, and Cantabro results we obtained. Production results mirrored those of the design data. Based on design criteria alone, the rejuvenator 40% RAP design outperformed our control mix design. There is some uncertainty surrounding repeatability of the IDEAL CT test, but as we progress and more tests are run and data compiled, I feel confident we can draw some conclusions.”
Superior plans to start the next high RAP project (using the PG 58S-28) during the week of July 15. More projects from other contractor members, including BMD with variations on gradations and lower RAP percentages, are in the planning stages. Look for updates on these additional projects in future Asphalt News editions.