Characterization of Highly Polymerized Alaskan Asphalt Binders and Mixtures

Abstract

Highly polymerized asphalt binders (HPABs) and mixtures have been used in recent years to address the cracking and rutting concerns due to varying climates and seasonal extreme conditions in Alaska. However, there has not been systematic characterization and performance data development for these materials. Hence, as presented in this paper, this study intends to systematically characterize the HPABs and mixtures and identify the performance benefits of these materials through laboratory tests and monitoring of field sections. Three HPABs (PG 52-40, PG 64-40, and PG 52-46) along with one unmodified asphalt binder (UAB) (PG 52-28) used in Alaska were used, and their morphologies and chemical and rheological properties were evaluated. The Fourier-transform infrared spectroscopy (FTIR) spectra and fluorescence microscopy (FM) morphology results presented the unique chemical functional groups of HPABs and the biphasic structure found with polymers distributed in the HPABs, respectively. The bending bean rheometer (BBR) and asphalt binder cracking device (ABCD) test results indicated that the HPABs apparently had lower (colder) cracking temperatures (i.e., better low-temperature cracking resistance) than the UAB. The multiple stress creep recovery (MSCR) test results showed that the HPABs had better rutting resistance than the UAB, as predicted by lower Jnr but higher %R values. The G* master curves illustrated that the HPABs were softer and less temperature susceptible than the UAB at intermediate temperatures, which implied better fatigue cracking resistance. The laboratory evaluation of performance of asphalt mixtures also confirmed that the asphalt mixtures with PG 52-40 and PG 64-40 had better resistance to rutting and low-temperature cracking than the mixture with PG 52-28. These results were further confirmed through field surveys of recent paving projects constructed in Alaska and data from pavement sections in the Long-Term Pavement Performance program database.