Strength Assessment of Flexible Pavement Incorporating Waste Plastic and Quarry Dust as Reinforcement Materials

The growing demand for road infrastructure has intensified the need for sustainable and resource-efficient construction practices. Conventional flexible pavements predominantly depend on non-renewable materials such as natural aggregates and bitumen, whose large-scale extraction leads to environmental degradation. At the same time, the rapid accumulation of plastic waste and quarry dust has emerged as a major ecological concern due to improper disposal practices. Addressing these dual challenges, the present study explores an innovative and environmentally responsible approach by utilizing shredded waste plastic as a partial replacement for bitumen and quarry dust as a supplementary mineral filler in bituminous mixes. The materials were selected considering their physical, chemical, and environmental attributes, along with their wide availability. A comprehensive laboratory program—including Marshall Stability, California Bearing Ratio (CBR), moisture susceptibility, and volumetric property analyses—was conducted to evaluate the performance of modified mixes with varying proportions of waste plastic and quarry dust. The experimental results demonstrate that incorporating waste plastic significantly enhances the binding capacity, stiffness, and rutting resistance of the pavement mix, contributing to improved strength and durability. Quarry dust, when used as a filler, effectively increases mix density, reduces air voids, and enhances the overall stability of the bituminous layer. The modified mixes exhibited superior load-bearing capacity, greater resistance to moisture-induced damage, and improved structural performance compared to conventional mixes. Overall, the integration of waste plastic and quarry dust promotes sustainable pavement construction by reducing environmental pollution, minimizing reliance on natural resources, and supporting the principles of green engineering and circular economy in civil infrastructure.