Effects of In-Place Volumetric Properties on Field Rutting and Cracking Performance of Asphalt Pavement

The effects of in-place volumetric properties on the rutting and cracking of asphalt pavement are of great interest to the pavement industry. As such, the major objectives of this paper are to determine the volumetric properties that correlate with field rutting and cracking and to quantify the field performance difference between low and high magnitudes of the determined volumetric properties. This study included 71 pavement sections from 24 field test roads that were part of the National Cooperative Highway Research Program (NCHRP) 09-49A project and covered different mix designs, volumetric property ranges, pavement ages, and four climate zones across the United States. The volumetric properties investigated are in-place air voids, voids in mineral aggregate (VMA), voids filled with asphalt (VFA), asphalt film thickness, and effective binder content ($V_{be}$). Rutting and cracking (transverse and longitudinal) performance data for all the test sections were collected in accordance with the Long-Term Pavement Performance program’s Distress Survey Manual. The authors identified the volumetric properties that correlated well with field performance and determined threshold values using the fuzzy clustering method to divide the identified volumetric properties into two groups: one with relatively small values, and the other with relatively large values. The rutting and cracking between the two groups were then compared. The results indicate that in wet climate areas, higher in-place air void percentages and lower VFA values correlate with more top-down longitudinal cracking. The sensitivity of the in-place air voids was sufficient to distinguish differences in cracking, whereas VFA sensitivity was not able to do so. Also, thicker asphalt film correlated with less field transverse cracking. The variables that clearly affected rutting were the VMA and $V_{be}$, whereby lower $V_{be}$ values indicated better rutting resistance. However, $V_{be}$ was unable to distinguish rut depths of various magnitudes. The effect of VMA on rut depth is complicated and there might be a sensitive range of VMA within which the rutting resistance of asphalt pavement can be more sensitive.