Development of high performing hybrid hot mix asphalt mixtures

In this study, mixture design volumetrics, moisture-induced damage and fatigue characteristics of hybrid hot mix asphalt (HMA) fabricated with crumb rubber (CRM) and polyvinyl alcohol (PVA) fibre were evaluated. Indirect tensile strength test was conducted to assess several tensile and fracture attributes of control, polymer-modified, CRM-modified, PVA-reinforced and hybrid HMA. Long-term performance of aged hybrid HMA was also assessed using flexural beam fatigue test. Comparison of mixture designs indicated a change in volumetric properties of hybrid mixture with acceptable resistance to stripping. Experimental results revealed that fracture energy and dissipated creep-strain energy of the HMA with 2%CRM and 0.2%PVA doubled relative to polymer-modified HMA. The developed hybrid HMA presented around 29 times higher resistance to repeated load failure with 90% reduction in crack propagation rate and over 12 times higher energy for unit crack propagation compared to conventional HMA. Additionally, effective fibre bridging across the crack and adequate coating of asphalt on CRM through image analysis revealed wider strain distribution, a perverse intricate fracture pattern and better adhesion. The higher fracture resistance, toughness indices, and resilience under repetitive traffic loading of hybrid mixtures could be effective in extending the service-life and enhancing long-term performance of flexible pavements.