Influencing factors and evaluation methods of reinforcement effect of fiber‐modified asphalt binder

Abstract The reinforcement of fiber is the linchpin of improving the strength of the asphalt binder and its mixture. This study aims to evaluate the reinforced shear effect and influence factors of fiber materials (i.e., lignin fiber, basalt fiber, polyester fiber, and hybrid fiber) by the self‐developed direct shear test. The micro‐reinforcement mechanism of fiber was explained based on the scanning electron microscope and basket leak test. Besides, the effects of fiber type, content, loading temperature, and rate on the asphalt binder's shear strength were analyzed systemically. The results indicate that the direct shear strength of asphalt binder was positively correlated with fiber content and loading rate but negatively associated with temperature. Meanwhile, when the fiber content is too large, the raise of shear strength will decrease. Gray entropy correlation analysis shows that the fiber type had the most effective influence on the binder's shear strength. The four fibers' reinforcing effects in descending order were composite fiber, polyester fiber, basalt fiber, and lignin fiber. Based on the growth rate of direct shear strength, the optimal lignin and basalt fiber content was 7%, polyester fiber was 6%–7%, and composite fiber was 6%. Furthermore, lignin fiber and basalt fiber were more sensitive to temperature, while polyester fiber had a better mid‐temperature weather resistance. Composite fibers and basalt fibers performed more stable behavior at high loading rates, decreasing 39% and 40%, respectively. Polyester fibers were stable when applied to the low loading rates, with an attenuation rate of 42%.