Improvement of properties of styrene–butadiene–styrene-modified bitumen by grafted eucommia ulmoides gum

In order to enhance the properties of styrene–butadiene–styrene (SBS)-modified bitumen and also alleviate the reliance of macromolecule-based modifier on crude oil production capacity and price, a natural modifier, referred to as eucommia ulmoides gum (EUG) is investigated as a partial substitute of SBS in this study. The grafting technology is used to form a functional group, i.e. maleic anhydride, which can effectively react with the nitro group in bitumen. Physical properties of the grafted EUG are examined based on infrared spectrum analysis. The mechanism of modifying bitumen by grafted EUG is also thoroughly studied. In addition, a series of laboratory tests are conducted to compare the properties of bitumen with different modification conditions. Furthermore, performance tests are conducted to investigate the high- and low-temperature properties and ageing property of mixtures with bitumen modified by different modifier combinations. It is found that the overall properties can be improved with appropriate amount of grafted EUG dosage. In particular, a dosage of 1.5% grafted EUG is recommended as an optimal amount in this study. It is suggested that the replacement of partial SBS by grafted EUG can not only enhance bitumen binder and mixture properties but also contribute to more sustainability with less energy consumption and carbon emission.