Improving Aramid Fiber Dispersion in Fiber Modified Asphalt Mixtures

Abstract: Aramid fiber, known for its lightweight and high strength, significantly enhances the mechanical properties of asphalt mixtures by improving resistance to cracking, rutting, and fatigue. However, its poor dispersion during the lab mixing process can reduce the observed benefits. This study focused on improving fiber dispersion and evaluating its effect on fatigue performance. A new lab mixing method and dispersibility evaluation index were introduced, effectively resolving indoor laboratory mixing challenges for aramid fibers. This new method was compared against other, more traditional methods of laboratory compaction. The new method was shown to increase fiber dispersion from approximately 20% with the traditional method to 70% with the new method. Key factors influencing fiber dispersion were analyzed, and tests showed that improved dispersion positively affects the fatigue resistance of asphalt mixtures. Testing consisted of dynamic modulus testing via AASHTO TP 132 and cyclic fatigue testing via AASHTO T 411. The FlexPAVE™ program was used to analyze the potential impacts to pavement performance from the different levels of dispersion in the mixing methods. It was found that the proposed three-layer dispersion with coarse aggregate method significantly enhanced fiber dispersion, resulting in improved fatigue resistance of asphalt pavements. The benefits of aramid fibers become even more pronounced in mixtures with larger nominal maximum aggregate sizes, making them effective in extending pavement lifespan and as a consequence, likely reducing reducing maintenance costs.