The volumetric mix-design of porous asphalt: an Italian study of Ndesign determination

The Superpave mix-design of asphalt mixtures using the gyratory compactor is a procedure used to define the proportion of materials on the basis of specific volumetric parameters. In Superpave, the number of gyrations, Ndesign, is important because it represents the compactive effort that produces a test sample with voids properties similar to those that the same mix would experience in the field. The main objective of this study was to determine the Ndesign number of gyrations required to duplicate the field density obtained with porous asphalt and to compare this value with the Ndesign required by Italian specifications. The experimental research was carried out considering in particular a porous asphalt layered into pavements of the important A18 motorway in Sicily. All field samples were obtained from the wearing course layered with different compaction levels.This paper reports the first experimental results and some considerations on the relationship be-tween Ndesign and compaction level.