Cement Kiln Dust with Fine Volcanic Ash as Substitute Fillers for Hot Mix Asphalt

Waste and by-product materials are often used as substitutes for raw materials in asphalt mixtures to lessen building costs, minimize environmental problems, and protect natural resources. This study investigates the feasibility of employing two kinds of ashes, fine volcanic ash (FVA) and cement kiln dust (CKD), which are abundantly available in various regions of Yemen, as substitute hot mix asphalt filler (HMA) for conventional fillers. A traditional filler, basalt filler (BF), was partially and totally replaced at different percentages. FVA replaced 15%, 30%, 45%, 60%, and 100% by weight of the filler. CKD replaced the traditional filler with 25%, 50%, 75%, and 100% by weight of fillers as a partial replacement. The total replacement of traditional fillers includes 20% CKD + 80% FVA, 40% CKD + 60% FVA, 60% CKD + 40% FVA, and 80% CKD + 20% FVA. The evaluation of the planned HMA was done using conventional mechanical and volumetric characteristics. Marshall stability, direct compression (DC) tests, and indirect tensile strength (ITS) were employed to evaluate the influence of FVA with CKD fillers on the asphalt mixture’s mechanical characteristics. The outcomes of the experiment demonstrated that 60% CKD + 40% FVA was used instead of the traditional mineral filler. A novel HMA was introduced, demonstrating enhanced stability, increased bulk density, decreased voids filled with bitumen (VFB), and lower flow compared to the mixture used as a control. Results showed that FVA and CKD may respectively substitute 30% and 75% of the BF. The ITS and the DC exhibited an increase. Therefore, incorporating CKD and FVA as fillers in is a sustainable solution that enhances performance, durability, and environmental benefits in asphalt construction.