Utilization of Plastic Solid Waste in Road Construction

The increasing generation of plastic solid waste has become a major environmental concern due to its limited biodegradability and improper disposal. Plastic is widely used because of its low cost, durability, and versatility, but a large share of the resulting waste is landfilled, openly dumped, or burned, which leads to land pollution, water pollution, and health-related problems. At the same time, the construction of flexible pavements requires large quantities of aggregates and bituminous materials, and the continuous demand for these conventional materials increases the consumption of natural resources and the environmental impact of their extraction and transportation. The utilization of waste plastic in road construction provides an alternative approach for managing plastic waste while improving the performance of bituminous pavement materials. This paper reviews the use of processed plastic waste in bituminous road construction, with particular emphasis on the method of incorporating plastic into heated aggregates and its interaction with bitumen. In the reviewed studies, waste plastic such as packaging materials, bags, and bottles is collected, cleaned, shredded to a suitable size, and added to heated aggregates so that it coats the aggregate surface before bitumen is mixed in. Various studies related to the use of waste plastic have reported changes in pavement properties such as stability, resistance to moisture damage, deformation resistance, and durability. Laboratory evaluations commonly rely on tests such as Marshall stability, flow value, density, indirect tensile strength, and retained stability, and a field comparison in Pune city reported slower deterioration of plastic-modified roads than conventional bituminous roads. The study also considers the environmental benefits, material requirements, processing methods, and practical limitations associated with plastic-modified roads. The performance of plastic-modified pavement is found to depend on the type of plastic, the quantity used, the particle size, the mixing temperature, and the method of incorporation, so an optimum plastic content must be maintained to obtain better performance without affecting the workability of the mix. The objectives of this review are to study the utilization of plastic solid waste in road construction, to examine the methods of using plastic in roads, to analyze its effect on pavement properties, and to evaluate its environmental benefits. The literature considered covers studies on plastic-modified bituminous mixes, their comparison with conventional mixes, and a review of the dry process in which shredded plastic is mixed directly with heated aggregates. Across these studies, the plastic coating on the aggregates is reported to reduce the penetration of water into the pavement, improve resistance to deformation and temperature variations, and enhance the overall service life of the road. Because most plastic is non-biodegradable, converting it into a useful construction resource also reduces the environmental burden caused by its improper disposal and lowers the dependence on conventional pavement materials. The utilization of suitable waste plastic in road construction can therefore provide a useful pathway for recovering plastic waste and supporting more sustainable pavement development. The paper summarizes the findings of selected studies on plastic-modified bituminous mixes and discusses the importance of proper processing, optimum plastic content, mixing temperature, and quality control in obtaining satisfactory pavement performance. Overall, the reviewed literature indicates that plastic-modified roads can offer both engineering and environmental benefits, including reduced consumption of bitumen and natural resources and a reduction in the amount of plastic waste disposed of in landfills and open areas.