Relationship between Air Voids and Permeability: Effect on Water Scouring Resistance in HMA

This study explored the relationship between air voids and permeability, and investigated the correlation between air void type, coefficient of permeability, mechanical properties, and moisture damage in hot-mix asphalt (HMA). Six asphalt mixtures were prepared with air voids ranging from 4% to 19% in increments of 3%. Major tests, including two air void tests, a penetration test, and a dynamic water scouring test, were conducted to assess the moisture damage by measuring and comparing the difference in air voids and permeability before and after the dynamic water scouring. A compressive test was conducted to evaluate the residual strength of HMA with different porosities. Results indicated that the effective voids and coefficient of permeability had a strong correlation. There was an obvious increase of effective voids and permeability for specimens with air voids from 10% to 13% after dynamic water scouring tests. In terms of compressive strength, specimens with air voids from 7% to 13% had greater strength loss and deformation than other specimens, indicating that moisture damage occurred and developed rapidly in asphalt mixtures within a certain porosity range.