Impact of Additives on Low-Temperature Cracking Properties of Soft Binders Used in Cold Regions

AbstractLow-temperature cracking is the main distress in asphalt pavement in cold regions (such as the arctic and subarctic regions) as the climate in these areas is severe in winter. While soft asphalt binders (such as PG 52-34 and PG 52-28) are used in the cold regions, asphalt pavements can still exhibit premature cracking failures. One of the approaches to solve this issue is to modify binders using additives. However, it is not clear which additives can significantly improve the thermal cracking resistance of binders. Therefore, there is a need to find potential additives resulting in improved resistance to thermal cracking because of extreme low temperatures experienced in cold regions. In this study, five additives [nano TiO2, nano SiO2, styrene-butadiene-styrene (SBS), ground tire rubber (GTR), and corn oil-based softening agent (SA)] were applied at various dosages with two soft base binders (PG 52-28 and PG 64E-40). Performance properties of modified binders were evaluated using the dynamic shear rheometer (DSR), standard bending beam rheometer (BBR), and modified BBR. The testing results indicated that the combination of a 7% softening agent and 7.5% SBS exhibited the highest improvement in the resistance to thermal cracking. Meanwhile, this combination also resulted in two performance grade bumps at high temperatures. Based on the laboratory testing results, the combination of a softening agent and high SBS could be potential additives to create high-performance binders for cold regions.