Effects of Recycled Concrete Dust on the Behaviour of Hot Mix Asphalt

Abstract

The increasing demand for sustainable pavement materials has encouraged the utilization of construction and demolition waste in asphalt mixtures. This study investigated the effects of recycled concrete dust (RCD), derived from demolished concrete, on the behaviour and performance of hot mix asphalt (HMA). The RCD was used as a replacement for conventional stone dust filler at proportion of 0%, 25%, 50%, 75%, and 100% using the Marshall mix design method in accordance with relevant ASTM standards. The performance of the mixtures was evaluated in terms of Marshall and volumetric properties, rutting resistance, cracking and moisture damage resistance. Results show that the OBC increased consistently with increasing RCD content due to the lower specific gravity and cementitious nature of RCD, with statistical analysis confirming the significance of this effect. The Marshall and volumetric analysis revealed improved mixture densification up to 75% RCD replacement, as evidenced by higher bulk density, reduced air voids, lower VMA, and increased voids filled with bitumen. Marshall test results indicated that moderate RCD replacement (25–50%) enhanced stability. Flow values decreased with increasing RCD, indicating stiffer mixtures without exceeding specification limits. Rutting resistance, assessed using the Marshall Quotient, improved substantially with increasing RCD content, demonstrating enhanced resistance to permanent deformation. Conversely, indirect tensile strength results showed a reduction in value at higher RCD contents, attributed to increased mixture stiffness. However, moisture susceptibility performance improved with RCD incorporation, with most RCD-modified mixtures exhibiting tensile strength ratio values above 75%, indicating strong resistance to moisture-induced damage. Overall, the findings demonstrate that recycled concrete dust can be effectively used as a sustainable filler in hot mix asphalt. The study supports the adoption of RCD in asphalt pavement construction as a viable approach for enhancing sustainability and reducing environmental impacts.