Value-Add Application of Plastic Waste in Porous Asphalt Mixture

Plastic waste has the highest un-recycled proportion among the solid wastes in Singapore. Given Singapore’s densely populated living environment and small land area with limited natural resources, sustainable development is critical to the nation’s progress. Utilisation of plastic waste in road pavement construction may become an alternative solution to reduce the amount of plastic waste in the landfill. This study evaluates the utilisation of waste plastic as additive materials in porous asphalt mixture (PAM). PAM is a type of asphalt mixture that possesses high voids content, usually above 18%, hence surface runoff can permeate through the pavement surface. Due to the high voids content, PAM is generally weaker than dense-graded asphalt mixtures. Herein, polypropylene (PP) plastic was added into the mixtures to improve the performance of PAM. Jurong sedimentary rock (JSR) was utilised as aggregates in this study as these materials are abundant in Singapore. PAM containing JSR with three different proportions of PP plastic that are 0%, 5%, and 10%, was fabricated. Meanwhile, PAM containing granite and 0% PP plastic was also produced as a reference mixture. A series of laboratory measurements, including Marshall, moisture susceptibility, resilient modulus, and creep tests, were conducted to assess the properties of PAM. The results indicated that adding PP plastic into the mixtures improves the mechanical properties of PAM, such as higher values of stability and moisture susceptibility, resilient modulus and resistance to deformation. Herein, waste plastic has promising feasibility to be utilised as additive materials in porous asphalt mixtures.