Determining Optimum Number of Gyrations for Porous Asphalt Mixtures Using Superpave Gyratory Compactor

The compaction characteristics of porous asphalt (PA) mixtures are significantly different from those of traditional dense-graded asphalt mixtures. Compaction efforts are critical for PA mixtures to exhibit good performance in terms of strength, functionality, and durability. The objective of this study was to determine the optimum number of gyrations for typical PA mixtures compacted using a Superpave gyratory compactor. The compaction characteristics and the influence of seven gyration levels on the indicators of air voids (AV) content, Marshall Stability (MS), multi-directional permeability, stone-on-stone contact, and durability of PA mixture were investigated through laboratory experiments. A multi-directional permeameter was designed to evaluate the multi-directional permeability of PA mixtures, including vertical, horizontal, and combined horizontal-vertical permeability. The AV content, multi-directional permeability decreases with the increasing gyrations. Based on the requirements of each indicator, the minimum and maximum gyrations for each indicator were determined. Balancing the performance of strength, functionality, and durability, the optimum number of gyrations for the PA mixtures was determined to be between 45 and 75 gyrations, which allows for different gyrations depending on the application of the PA mixture. Finally, the requirements of MS, horizontal permeability, and combined horizontal-vertical permeability are recommended for improving the performance of PA mixture.