National standards for the Superpave system are published and maintained by AASHTO through the Subcommittee on Materials (SOM). The Subcommittee, with membership from all 50 states, held its annual meeting last August in Duluth, Minnesota. Rick Harvey, of Wyoming, chairs the SOM Technical Section for Asphalt Mixes. At the August meeting, Mr. Harvey established a five-state Task Force to consider, prepare and recommend changes to mix design standards for balloting by the entire Subcommittee. It should be noted that several Task Force members are also members of either the AASHTO Lead State Team or the Mix ETG and some are members of both.

In making its recommendations, the Task Force was charged with considering changes proposed from among several sources, including:

• NCHRP 9-9: "Refinement of Superpave Gyratory Compaction Procedure"
• 1998 Lead State Guidance (June 1998)
• Input from the Mix ETG
• Suggestions by member States

The Task Force completed its work in November and forwarded proposed revisions of four standards to Chairman Harvey and Dr. Haleem Tahir at AASHTO headquarters. Dr. Tahir prepared the final ballot, which has been distributed to the entire Subcommittee on Materials for voting. It's expected that most, if not all, the proposed improvements will be approved. Ballot returns are due to AASHTO by February 6, 1999.

The standards to be improved include:

• MP2: Standard Specifications for Superpave Volumetric Mix Design
• PP2: Standard Practice for Short and Long Term Aging of Hot Mix Asphalt (HMA)
• PP28: Standard Practice for Designing Superpave HMA
• TP4: Standard Method for Preparing and Determining the Density of Hot Mix Asphalt (HMA) Specimens by Means of the SHRP Gyratory Compactor

The standard revisions, based on a combination of research, expert opinion and practical experience, are intended to clarify and simplify the mix design process, and improve the resulting product.

Highlights of the proposed changes include:

• Reduction of Mix Design Levels from seven to four
• Adjustment of the N-design table to include more appropriate design levels and gyrations
• Designs based on 20 year ESAL projections
• Increased density allowed at N-initial for low-ESAL designs
• Compaction to N (design) rather than N (maximum)
• Simplified and shortened procedures for short-term aging

The Task Force included Ronald Sines (New York), Larry Michael (Maryland), Eileen Connolly (New Jersey), Cecil Jones (North Carolina), and Wade Bentenson (Utah). The Mix ETG participated in the development of the ballot and provided comment on its content.

Special acknowledgment is extended to Ronald Sines of the NYSDOT Materials Bureau. Mr. Sines chaired the Task Force, synthesized the recommendations, managed its review and modification, and prepared the final recommendation package. Similar acknowledgment is extended to Dr. Haleem Tahir, of the AASHTO staff, who prepared the final ballot, will manage its administration, and ultimately revise and publish the improved standards in accord with the direction of the Subcommittee on Materials and Mr. Harvey. Also, the FHWA should be recognized for their full partnership with AASHTO in the facilitation and support of the activities of both the Mix ETG, the Lead State Team, and the Task Force.

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