Superpave Design Compaction Effort: Validity of Using Density at the End of Service Life as Parameter to Define N-Design

摘要

When the Superpave method of mix design was introduced in 1993, the method included a new Superpave gyratory compactor and a table of design compaction effort based on the premise that density in the laboratory compactor should match density at the end of service life. The experiment underpinning the N-design was done on pavements at least 12 years old. Post SHRP attempts to expand that database to include pavements of all ages and refine the table of design compaction have been unsuccessful and lead to the conclusion that density at the end of service life is not a reasonable parameter to define design compaction. The Superpave Mixtures and Aggregates Expert Task Group have recommended changes to the original design compaction. These are based on compactability of the aggregate skeleton to changes in N-design and on changes in mixture stiffness with changes in N-design. Change to the design compaction level (N-design) does not change asphalt content, it changes mixture mechanical properties (stiffness). Current levels of N-design in the Superpave system are rational and reasonable.