Development of 4.75mm Superpave Mixes: Fid-Bau Portal

Development of 4.75mm Superpave Mixes

S. G. Williams

Until recently, the Superpave asphalt mix design specification did not include the 4.75mm nominal maximum aggregate size (NMAS). Such mixes have the potential to create a smooth riding surface, extend pavement life, improve ride quality, improve safety characteristics, enhance appearance, increase durability, reduce permeability, and reduce road-tire noise. Also, because of the ability to place these mixes in thin lifts, they can be used to correct surface defects, decrease construction time, decrease construction costs, and to extend maintenance dollars. The Arkansas State Highway and Transportation Department does not currently use a 4.57mm NMAS mix. Thus, the objectives of this project were to evaluate the benefits and impacts associated with 4.75mm mixture implementation. In this study, three aggregate sources (limestone, sandstone, and syenite) were used to develop 4.75mm nominal maximum aggregate size (NMAS) mixtures. From each source, six mixtures were designed at varying design air void contents and design compaction level. Two air void levels (4.5 and 6.0 percent) and three compaction levels (Ndes=50, 75, and 100) were evaluated in order to determine the most advantageous design parameters with respect to rutting, stripping, and permeability. Also, the use of natural sand was investigated.