State-Wide Asphalt Co-Op Meeting

VDOT and VAA representatives met on December 15 at Germanna Community College’s Daniel Center in Culpeper to discuss various asphalt related issues. At the meeting, VAA had representative from across the state; VDOT had members from different central office divisions, districts and the transportation research council.  The discussion at the co-op focused on a few main areas – 2017 schedule specifications, on-going research, and new initiatives.s.

 

The 2017 plant mix schedules have several changes and nuisances. First, the proposals will have a Volume I and Volume II as previous years. However, the Volume II will be the same as the 2016 schedules where supplemental specifications modify specifications from the 2007 Road and Bridges spec book. Volume I will have any new special provisions, copied notes or supplemental specifications to the 2007 spec book. Changes in Volume I will supersede Volume II. Second, Volume I will have the new asphalt density specification and the AC content incentive spec. Both specs give the contractor an opportunity to achieve a 5% bonus for meeting the requirements. The goals are to produce a more consistent mix at the plant and to achieve higher and more consistent compaction levels at the project. The primary discussion in the co-op revolved around using daily Rice values or moving average of 5 Rice values to calculate percent density. The asphalt density specification language requires daily Rice values be used, which is a change from current practice. Finally, plant mix schedules will have a longitudinal joint straightness specification. This new requirement places limits on the amount of deviation allowed along tangent sections and curves.

 

Various research projects are ongoing. VDOT teamed with FHWA and S.L. Williamson to perform a high-density field demonstration project. Results from this project and other FHWA demonstration projects around the country will be documents in a FHWA report later this year. VTRC is continuing their efforts to assess the impacts of mix changes and pilot specifications on in-place density and lab performance. Preliminary results are encouraging, but a final report will not be completed until all lab testing and analysis is completed. Along with this project, VTRC is completing the lab testing comparing the 65 vs. 50 gyration mixes sampled in 2015.

 

Lastly, several new initiatives were discussed. First, VDOT and VAA established a task force to look at sub-division mixes to improve performance. The task force is scheduled to meet in the next month or two. Next, it was suggested that VDOT, contractor and consultant labs perform a round-robin on mix testing. VDOT and VAA members will explore the possibility and report back to the co-op at the next Co-Op meeting. Finally, VAA proposed the Secondary and Sub-Division manual be updated to include cold recycled mixes. Several parts of the state have excess milling piles and they continue to grow.

VDOT and NCAT research has documented the performance of these mixes. Updating the manual to list the mix, the material thickness equivalents and the default pavement structures will result in more use of cold recycled asphalt mixes, help reduce the milling piles, and reduce construction costs while not compromising pavement performance.

 

The next co-op meeting is scheduled for April.