Modifying laboratory mixture design to improve field compaction

Abstract

Field data collected in Indiana suggest that if asphalt mixtures were designed to be more compactable in the field, they could be compacted to a field density equivalent to the laboratory mixture design density, potentially increasing pavement durability. The objective of this research was to modify the mixture design in order to increase in-place mixture density without sacrificing permanent deformation characteristics. Three 100-gyration mixtures were used, each meeting applicable specifications and designed according to AASHTO M323. For each mixture, additional designs were completed using 30, 50, and 70 gyrations. Optimum binder content for these mixtures was chosen at 5% air voids, rather than 4%, and the effective binder content was held constant. Results indicate that the mixture produced using 30, 50, and 70 gyrations had equal or better permanent deformation characteristics than the original 100-gyration mixtures. A trial field project confirmed that mixtures designed at 5% air voids could be compacted to this level, showing that the approach is feasible from a construction viewpoint.