Mechanistic Characteristics of Asphalt Binder and Asphalt Matrix Modified with Nano-Fibers

Abstract

The Hot Mix Asphalt (HMA) mainly consists of air voids, coarse aggregate and asphalt matrix (AM), which includes asphalt cement (AC) and fine aggregates. The coarse aggregate is stiffer than the AM and is elastic in nature, whereas, the AM makes the HMA a visco-elastic material. The AM is considerably weaker than the coarse aggregate and highly susceptible to damage due to external loads and environment. This study focuses on the preparation and mechanistic characterization of AC and AM mixtures modified with Carbon Nano-fibers (CNF). The AM mixtures were made using lime-stone aggregates and three AC types, neat, processed and CNF-modified. The AC was modified with varying percentage of CNF by weight of AC. To achieve the highest degree of CNF dispersion in AC, two different dispersion techniques were utilized. First, the CNF were sonicated for a specified time to initially disperse them into a solvent. Then the mixture was mixed with AC using a mechanical mixer at medium to high temperature. The dynamic shear rheometer was utilized to determine complex shear modulus (G*) and creep compliance (J[t]) of AC and AM mixtures for a range of temperatures and loading frequencies. The G*-master curve and J[t] analysis revealed that the AC modified with CNF significantly improves the visco-elastic response of the AC and AM. It is recommended to expand the research to different types of aggregate, aggregate gradation, and types of asphalt in order to identify key parameters that can facilitate the understanding of improvements in HMA performance using nano-fibers.