Study of the Possibility to Reuse Waste Plastic Bags as a Modifier for Asphalt Mixtures Properties (Binder Course Layer)

Abstract

Use of recycled waste materials in road pavements is nowadays considered not only as a positive option in terms of sustainability, but also, as an attractive option in means of providing enhanced performance in service. This is especially true in the case of recycled plastics. Thin plastic bags are mainly composed of low density Polyethylene (LDPE) and it’s commonly used for packaging, protecting and many other applications. However disposal of waste plastic bags (WPB) in large quantities constitutes an environmental problem, as they considered non-biodegradable materials. Hence, there is a real need to find useful applications for these growing quantities of wastes. In this research, Waste Plastic Bags (WPB) as one form of polymers are used to investigate the potential prospects to enhance asphalt mixture properties. Study aims include studying the effect of adding different percentages of grinded WPB as an aggregate coat on the properties of asphalt mix comparing it with conventional mix properties besides identifying the optimum percent of WPB to be added in the hot mix asphalt. WPB were introduced in the asphalt mixture in grinded form (2 - 4.75 mm). Marshal mix design procedure was used, first to determine the Optimum Bitumen Content (OBC) and then further to test the modified mixture properties. In total, (47) samples were prepared, 15 samples were used to determine the OBC and the remaining were used to investigate the effects adding different WPB percentages to asphalt mix. The OBC was 5.1 % by weight of asphalt mix. Seven proportions of WPB by weight of OBC were tested (6, 8, 10, 12, 14, 16 and 18%), besides testing of ordinary asphalt mix. Tests include the determination of stability, bulk density, flow and air voids. Results indicated that WPB can be conveniently used as a modifier for asphalt mixes as a part of sustainable management of plastic waste as well as for improved performance of asphalt mix. WPB content of 9.0 % by weight of OBC is recommended as the optimum WPB content for the improvement of performance of asphalt mix. Asphalt mix modified with 9.0 % WPB by OBC weight has approximately 24 % higher stability value compared to the conventional asphalt mix. Asphalt mix modified with higher percentages of WPB exhibit lower bulk density, higher flow and higher air voids. Study recommends local authorities to confirm using WPB in asphalt mix with the proposed percentage (9.0% by OBC weight) for improved performance of asphalt mix. Moreover, further studies are needed in various topics related to effective utilization and best incorporation techniques of waste materials.