PASSING THE TORCH

As the Superpave binder and mix design process moves from research to implementation by the year 2000, the industry is learning from its successes and problems. This article reviews some of the elements of change that are taking place in the Superpave process in the following categories: materials and mix design, plant operations, placement and compaction operations, field management, performance testing, and training. The Superpave aggregate consensus standards are specifications for high quality materials for use in hot mix asphalt (HMA) and should therefore have a positive effect on HMA performance. The Performance Graded binder specification proposed in Superpave provides a better system for graidng asphalt binders than has been used in the past. Superpave also recommends major changes in the mix design process. The use of gyratory compaction in conjunction with volumetric property controls are the cornerstones for the process. Plant operations currently being evaluated include stockpiling aggregates, feeding aggregates to the plant, storing binders, drying aggregates, mixing aggregates and binder, and storing the completed HMA. As with all mixes, the contractor must understand mixes and their relationship to compaction. An appropriate field management process is critical for the implementation of Superpave technology. The Superpave shear tester was developed as a tool to predict pavement performance. The process of training personnel in the HMA industry is under way, but much remains to be done in this effort to reach the estimated 300,000 workers.