Asphalt Binder Adaption for Climatic Conditions in Cold Regions: Alaska Experience

Asphalt binder adaptation in cold and spacious areas such as Alaska is critical because of varying climates and seasonal extreme conditions. To fully address the binder selection issues in Alaska, this paper presents a study that conducted analysis based on a long-term pavement performance (LTPP) database to reveal the climatic effects on binder selection, followed by evaluation of the laboratory and field performance of hot mix asphalt (HMA) containing neat binder and several currently used modified binders in Alaska. It was found that the recommended high performance grading (PG) grades for the entire Alaska are equal to or lower than 52°C, whereas the low grades in more than 76% of the recorded weather stations in Alaska are recommended to be lower than $-28°\mathrm{C}$. Laboratory testing results showed that HMA with high-end modified binders expressed higher rutting resistance than that containing the neat binder PG 52-28, and HMA with the neat binder displayed the lowest resistance to low-temperature cracking compared to modified binders. Field surveys suggested that increasing high temperature grade would improve rutting resistance in Alaska Department of Transportation and Public Facilities (ADOT&PF)’s Central Region, although there was not enough evidence to draw any conclusion on modified binders’ low-temperature performance in the Northern Region. It is recommended to keep using high-end modified binders in the Central Region and extend the low PG grade to $-46$ and/or $-52$ in trial projects in the Northern Region. In addition, more field projects covering different low-end modified binder grades in the Northern Region should be developed for better evaluation of low-temperature performance in that area. Furthermore, a systematic study of highly modified binders through both laboratory tests and field project monitoring is needed to provide more performance data and information for ADOT&PF to fully develop specifications of modified binders to better address the extremely climatic conditions in Alaska.