Laboratory Evaluation of Open-Graded Asphalt Mixes with Small Aggregates and Various Binders and Additives

An ongoing research effort seeks to develop alternative asphalt surface mixes that will be quiet and durable without sacrificing safety. The effects of several common combinations of binder type and additive on noise reduction and durability of an open-graded asphalt mix with small aggregate size were investigated. Five binder types and two additives were selected for a 4.75-mm nominal maximum aggregate size gradation. A series of laboratory tests was conducted to evaluate their performance-related pavement surface properties. Results showed that the use of polymer-modified or rubberized binders instead of unmodified binder in the 4.75-mm open-graded mixture reduced permeability but increased acoustic absorption, with the mixture containing asphalt rubber binder showing the most acoustic absorption improvement. The use of asphalt rubber could also increase the mixture resistance to moisture damage, premature failure, raveling, and rutting. There were preliminary indications of friction improvement by replacement of conventional binder with asphalt rubber binder in the small-size-aggregate, open-graded asphalt mix.