Relationship of Coefficient of Permeability, Porosity, and Air Voids in Fine-Graded HMA

Abstract

The purpose of this study was to determine the relationship between the coefficient of permeability, porosity, and voids in total mixture (VTM) of fine-graded hot-mix asphalt (HMA). Two fine-graded HMA mixtures used in Michigan were prepared with the same binder contents (5.5%) and nominal maximum aggregate sizes (NMAS) of 9.5 mm and 12.5 mm, respectively. For each mixture, laboratory specimens were fabricated using a superpave gyratory compactor (SGC) with 25, 50, and 75 gyrations, respectively. The coefficient of permeability increased as the air void and porosity values increased. After the first moisture conditioning, the porosity and coefficient of permeability increased for most of the specimens. After the second moisture conditioning, it was observed that specimens had a reduced porosity and coefficient of permeability. There were significant differences for porosity and permeability before and after the first moisture conditioning. However, there were no significant differences for porosity and permeability before and after the second moisture conditioning. Regarding moisture conditioning, the 12.5-mm gradation tended to have a more stable structure than the 9.5-mm gradation. This tendency was indirectly observed from the rutting performance test. This study is helpful in the design of asphalt mixtures that can resist pore pressure damage.