Long-term performance of chemically modified cotton straw fibers in micro-surfacing asphalt mixtures

Using agricultural wastes in asphalt pavements presents a promising solution to enhance pavement performance and utilize agricultural wastes simultaneously. In the paper, the fibers are made from recycled cotton stalks. Chemical modifiers are chosen to enhance the adherence of fiber asphalt binders. Different modified fibers are added to the SBR-modified emulsified asphalt. The modified asphalt binders are then utilized to prepare asphalt mixtures. Comparative studies on construction performance, road performance, and durability were carried out. Results showed that water consumption and bitumen aggregate ratio at the micro-surfacing were increased after adding fiber. Fibers with low hygroscopicity, rough surface, and high asphalt absorption rate had better adhesion properties. The long-term performance of a micro-surfacing mixture was most remarkably improved by the CH3COOH-modified cotton straw fibers, demonstrating a 10.07 % drop in rutting depth, a 9.13 % decrease in abrasion value, and a 41.13 % gain in shear resistance compared to the micro-surfacing mixtures with unmodified fibers. The study concluded that modified fiber micro-surfacing asphalt mixes are more suitable for seasonal frozen regions than the conventional mixes. The findings offer a theory foundation for the future development of cotton straw fibers in road engineering.