AI’s Mark Buncher, Bob Humer and Mark Blow were in attendance at the Spring Asphalt Binder ETG and Asphalt Mixture/Construction ETG Meetings held at the Beckman Center in Irvine, CA, February 24 – 27, 2009.
Frank Fee of NuStar Marketing LLC is Chairman of the Mixture ETG and Gaylon Baumgardner of Ergon Asphalt & Emulsions Inc. is Chairman of the Binder ETG. Minutes and agendas from these ETGs can be found on the AI website here.
On Friday, a one-day pilot workshop by Dr. Donald Christensen presenting the results of NCHRP 9-33 “A Mix Design Manual for Hot Mix Asphalt.” The main deliverables from 9-33 include a 363-page mix design manual and an elaborate Excel workbook entitled “HMA Tools” for performing mixture designs as outlined in the manual. Both are available online here. Frank Fee also serves as the Chairman of the 9-33 Technical Panel.
The 12 chapter mix design manual from NCHRP 9-33 covers everything from binders and aggregates to field adjustments and quality control of HMA mixtures. Although many of the specifications and methods contained in the manual are similar to Superpave, the manual is not intended to be the “new” Superpave. In an effort to ensure that that proper binder content and VMA are obtained in the final mix design, the process developed from 9-33 selects a fixed design binder content. This binder content is then maintained throughout the design process, which involves altering the aggregate gradation to obtain the targeted air voids and VMA in the mix. This approach generated extensive discussion.
The “HMA Tools” Excel workbook was also demonstrated. It is a very sophisticated and in-depth workbook that enables a mix design technician to complete a design in accordance with the mix design manual guidelines and includes binder blending computations needed for incorporating high volume RAP percentages into a mixture.