Influence of chemically-modified cotton straw fibers on the properties of asphalt mortar

Cotton straw fibers have an important influence on the performance of asphalt mixtures. However, the modification of cotton straw fibers and the performance characterization between the treated cotton straw fibers and asphalt are still lack of understanding. To obtain a better performance improvement technical scheme of cotton straw fibrous asphalt mortar. In this study, sodium hydroxide, silane coupling agent (KH550), and glacial acetic acid (CH3COOH) were used to modify the surface of cotton straw fibers. The modification mechanism and basic properties of the cotton straw fibers were investigated. The effect of the modified fibers on the performance of asphalt mortar was studied using cone penetration, softening point, ductility, and dynamic shear rheology tests. The results showed that the CH3COOH- and KH550-modified fibers produce new acetyl C-O and Si-O deformation vibration absorption peaks, respectively. The three modification methods destroy the hemicellulose structure in the cotton straw fibers. The post-modification surface impurities, roughness, and basic properties of the fibers are reduced, increased, and improved, respectively. An increasing cotton straw fiber dosage continuously improves the high temperature performance of asphalt mortar, but reduces ductility. A fiber dosage of 2 % yields optimized the high temperature performance and the ductility. Under this dosage, the CH3COOHmodified cotton straw fibrous asphalt mortar exhibits a better comprehensive performance. Its shear strength and softening point, as compared to the matrix asphalt increase by 3.21 times and 14.99 %, respectively, and the ductility reduces by 23.94 %, all the measured properties meet the technical specifications of road petroleum asphalt. The results provide more bases for the application of cotton straw fibers in road engineering.