Assessment of Volcanic Ash as a Filler Material in Hot-Mix Asphalt (HMA) using SUPERPAVE Methodology

Abstract

This study aimed to evaluate the performance and geotechnical suitability of volcanic ash fillers namely pumice and cinder as alternatives to conventional stone dust in Hot Mix Asphalt (HMA), using the SUPERPAVE mix design methodology. The motivation stemmed from the need for sustainable, locally available materials that can enhance pavement performance while reducing reliance on traditional fillers. A series of laboratory tests were conducted to assess the volumetric and mechanical properties of asphalt mixtures incorporating varying proportions of pumice and cinder as filler materials. These included evaluations of bulk and theoretical maximum specific gravity, voids in mineral aggregate (VMA), air voids (AV), voids filled with asphalt (VFA), moisture susceptibility through tensile strength ratio (TSR), and permanent deformation through creep stiffness index. The geotechnical properties of pumice and cinder were also assessed using maximum dry density (MDD), optimum moisture content (OMC), California Bearing Ratio (CBR), and swell potential. The results revealed that all mixtures containing volcanic ash fillers satisfied the SUPERPAVE design criteria. Cinder based mixtures closely mirrored the control mix with 100% stone dust in terms of compaction, stability, and stiffness, while pumice slightly increased air void content due to its lightweight and porous nature. Nonetheless, when blended appropriately, pumice still performed within acceptable limits. TSR values for all mixtures exceeded the minimum 80% requirement, confirming resistance to moisture-induced damage. Creep stiffness results for all mixes were well below the 0.5% deformation threshold set by the ERA Pavement Design Manual, indicating good rutting resistance. Geotechnically, both pumice and cinder demonstrated favorable CBR values above 30%, minimal swell and sufficient dry density for structural use, with cinder exhibiting particularly desirable compaction characteristics. The study concluded that volcanic ash materials, especially cinder, are technically viable and sustainable alternatives to stone dust in asphalt mixture design. Their use can enhance mixture performance and support environmentally conscious infrastructure development. It is recommended that bitumen content be adjusted when using pumice to compensate for its absorptive nature, and that further field performance evaluations be conducted to validate long-term behavior. The findings support broader adoption of locally sourced volcanic materials in flexible pavement construction as part of a sustainable engineering approach.