Influence of Aggregate Gradation on the Performance Properties of Porous Asphalt Mixtures

Abstract

This research investigated the effect of aggregate gradation on the performance of porous asphalt mixtures. Ten aggregate gradations, which represent typical gradations used by 20 different United States highway agencies for open graded friction courses, were compared by evaluating draindown, permeability, Cantabro abrasion loss, indirect tensile strength, and rutting resistance. The results indicated that gradation does influence the performance of porous asphalt mixtures. An increase in the void ratio of the aggregate structure contributes to significant increases in porosity and permeability. Consequently, the indirect tensile strength and durability (as measured by the Cantabro abrasion test) generally decreased as the mixture porosity increased. The 10 mixes showed good moisture resistance characteristics and most of the mixes had no significant difference in tensile strength after the moisture-conditioning procedure. Furthermore, the effects of rutting did not correlate with mixture or aggregate porosity. Based on these results, it is evident that an aggregate gradation for a porous asphalt mixture can be optimized depending upon the performance requirements (permeability or strength) based on the void ratio of the gradation.