Investigation and optimization of waste LDPE plastic as a modifier of asphalt mix for highway asphalt: Case of Ethiopian roads

Abstract Overwhelming increase in plastic waste since recent years became series ecological issue for both developed and developing countries. Compromising the large plastic waste potential in Ethiopia and poor pavement performance in the roads due to severe weather and high traffic loads, it is viewed to use this in-hand resource as asphalt modifier to urge sustainability, enhance the stability of asphalt mix and reduce the amount of bitumen used. The study aimed at investigating the effect of using waste LDPE plastic as a modifier of virgin bitumen. This study also tries to amplify the advantage of using wet blending method over dry. Four modified bitumen mixes prepared with 4, 6, 8 and 10% waste LDPE plastic content by the weight of optimum bitumen content (OBC) at different mixing temperatures (160, 170, and 180 °C) and different mixing times (1, 1.5 and 2 hours) to evaluate penetration point, softening point and ductility. 170 °C mixing temperature and 1.5 hour mixing time results, homogeneous mix between bitumen and waste LDPE plastic materials compared to other mixing temperatures and mixing times. Marshall Test Method was used to determine the optimum bitumen content and to evaluate the marshal properties of the plastic modified asphalt mix. The OBC of non-modified marshal sample was found to be 5.16% by weight of the total aggregate while the optimum waste LDPE modified bitumen content was found to be 6.5% by weight of the OBC. Asphalt mix modified with 6.5% of waste LDPE plastic content has 33.67% higher stability value compared to the non-modified asphalt mix.