Balanced mix design research and implementation update

Virginia’s road trip to performance-based asphalt specifications continues. As outlined in previous updates, two pilot projects were constructed during 2019. Testing and analysis by the VTRC for these efforts are ongoing. Takeaways from this effort include: performance test results improve when comparing production samples to mix design samples; a portion of the study is to determine the effect of reheating on performance test results. To date, the analysis is indicating that reheating has a negative impact on durability (Cantabro) results with a mixed impact on cracking results (CTindex). For 2020, BMD pilot projects remain on a volunteer basis. To date, Superior Paving Corp. and Colony Construction, Inc. have confirmed participation. However, it is clear that more volunteers are needed to evaluate the sampling/testing methodology fully, and more importantly, the impact on contractor/producer operations. VDOT indicates they are still holding to the 2023 implementation date. Stacey Diefenderfer of the Virginia Transportation Research Council (VTRC) states, “Much work is yet to be done. It is critical that we get as many pilot sections constructed this year as possible”. VDOT is planning more pilot projects in 2021. However, these pilots will be part of the paving schedule contracts, so now is the time to jump in a learn as much as you can while there is more flexibility.

Additionally, Boxley is now in full swing at the Heavy Vehicle Simulator site at the Virginia Tech Transportation Institute. Load testing is fully underway for the previously placed 30% RAP mix. Design work is nearing completion for the next two mixes, both mixes being BMD Optimized SM-9.5 mixes containing 45% RAP, with one also including a rejuvenator. The placement of these mixes is scheduled for mid-July. Look for more detail as this effort continues in future newsletters.