In the design of pavement infrastructure, the flow number is used to determine the suitability of a hot-mix asphalt mixture (HMA) to resist permanent deformation when used in flexible pavement. This study investigates the sensitivity of the flow numbers to the mix factors of eleven categories of HMAs used in flexible pavements. A total of 105 specimens were studied for these eleven categories of HMAs. For each category of asphalt mixture, the variations in flow number for different contractors, binder types, effective binder contents, air voids, voids in mineral aggregates, voids filled with asphalt, and asphalt contents were assessed statistically. The results show that the flow numbers for different types of HMA used in Colorado vary from 47 to 2272. The same mix may have statistically different flow numbers, regardless of the contractor. The flow number increases with increasing effective binder content, air voids, voids in mineral aggregates, voids filled with asphalt, and asphalt content in the study range of these parameters.

This study investigates the sensitivity of the mechanistic-empirical flexible pavement design performance parameters such as cracking, rutting, and smoothness to mix factors for 11 categories of hot-mix asphalt (HMA) mixtures. For each category of HMA mixture, the variations in the pavement performances for different effective binder content (Vbe), air void (Va), voids-in-mineral aggregates (VMA), voids-filled-with asphalt (VFA), and asphalt content (AC) are examined by the AASHTOWare Pavement Mechanistic-Empirical Design, simply the AASHTOWare software analysis. Five types of distresses: international roughness index (IRI), total rutting, rutting in the HMA layer, bottom-up fatigue cracking, and top-down longitudinal fatigue cracking are considered in the analysis. Results show that the prediction of distresses values after 20-year of service life using the AASHTOWare software may differ by up to 170% for different specimens of a certain mix design. All distresses, except rutting, increase in Va, VMA, and VFA. Rutting in HMA increases with an increase in VMA and VFA, and is insensitive to Vbe, Va, and AC in the study range of these parameters.