Waste LDPE modification of Dense Bituminous Mix (DBM), Marshall Performance, optimum LDPE dosage, and optimum binder content

The increasing accumulation of low-density polyethylene (LDPE) waste and the growing demand for durable and sustainable pavement infrastructure necessitate innovative approaches for incorporating waste plastics into road construction. This study experimentally investigates the effect of LDPE modification on the mechanical and volumetric properties of Dense Bituminous Mix (DBM). A conventional 60/70 penetration-grade bitumen was used as the reference binder, while LDPE was incorporated at different dosages of 2%, 4%, 6%, and 8% by weight of bitumen. Marshall mix design was employed to evaluate Marshall stability, flow value, bulk density, air voids, voids in mineral aggregate (VMA), and voids filled with bitumen (VFB). The experimental results indicate that LDPE modification improves the overall performance of the bituminous mixture, with 6% LDPE identified as the optimum modifier dosage based on the combined mechanical and volumetric characteristics. At this dosage, the Marshall stability increased to approximately 1450 kg, compared with 1255 kg for the conventional mixture, representing an improvement of approximately 15–16%. The flow value and bulk density also improved, reaching 2.80 mm and 2.420 g/cm³, respectively. The modified mixture exhibited approximately 4.2% air voids, while the VMA and VFB were approximately 15.27% and 73.29%, respectively. Furthermore, the optimum binder content decreased from approximately 5.5% for the conventional mixture to 5.0% for the LDPE-modified mixture, indicating the potential for reduced bitumen consumption. The findings demonstrate that optimized LDPE modification can enhance the load-bearing characteristics of DBM while simultaneously providing a beneficial route for the utilization of waste plastic in pavement construction. The proposed approach has potential to contribute to more sustainable and resource-efficient flexible pavement systems, although further validation through fatigue, rutting, moisture susceptibility, ageing, and fieldperformance studies is recommended.