Chemical Aging Indexes and Rheological Parameters for Cracking Susceptibility Evaluation of Alaskan Polymer-Modified Asphalt Binders

Asphalt oxidation induces asphalt binder embrittlement, which in turn increases the susceptibility of flexible pavement to fatigue and low-temperature cracking. It is critical to determine an index that can appropriately track the oxidation extent of asphalt binder and assess its cracking susceptibility. The objectives of this study are to investigate the connections between the chemical changes by oxidation with rheological parameters, and to identify suitable chemical aging indices and rheological parameters to assess the cracking susceptibility of Alaskan asphalt binders. A total of 13 typical Alaskan asphalt binders were collected from three different suppliers. The Glover-Rowe (G-R) parameter, rheological index (R-value), ΔT, and fatigue parameter (Nf) were selected as rheological parameters to quantify the change of cracking susceptibility of asphalt binder with aging. Fourier transform infrared spectroscopy (FTIR) technologies were applied to obtain the chemical aging indices such as the ratio of peak height between C=O and CH2 (C=O/CH2), Carbonyl Index, and Sulfoxide Index. The results indicated that the C=O/CH2 was the most effective chemical aging index to track the oxidation extent of asphalt binder. The G-R parameter was the most promising rheological index among the evaluated rheological parameters (i.e., G-R parameter, R-value, ΔT, and Nf) to evaluate the durability and cracking susceptibility of asphalt binder because it correlated well with the C=O/CH2. The R-value was not desirable in some cases due to the difficulty in calculation. The fatigue parameter (Nf) showed a weak correlation with the chemical aging indices. A fair correlation could be developed between ΔT and the C=O/CH2, but the correlation was not as strong as that developed for the G-R parameter