Selection of recycled waste plastic for incorporation in sustainable asphalt pavements: A novel multi-criteria screening tool based on 31 sources of plastic

Recent advances in the construction of sustainable asphalt roads with recycled plastic

“…14 MFI values are commonly used to assess the processability of plastics, where high MFI values refer to low-viscosity plastics and low MFI values refer to high-viscosity plastics. The MFI of EVA (28% VAc), a polymer commonly used for bitumen modification, 10 is comparable to that of virgin PP at 190 °C, 7.2 and 7.5 g (10 min) −1 , respectively, whereas virgin LDPE is more viscous with an MFI at 190 °C of 1.7 g (10 min) −1 , 23 showing that PP is theoretically more suitable than LDPE for bitumen modification. However, the original plastic grade, the presence of fillers and multiple plastic streams in recycled plastics can increase or decrease their viscosity (Fig.…”

“…23 The composition and chemical and physical properties of the recycled plastics were used to rank the recycled plastics against virgin plastics and EVA, a polymer commonly used for bitumen modification, which ranked higher than all the other plastic sources. 23 Another scoring system was recently presented to assess the recycling quality of end-oflife plastics for a specific application based on the plastic of interest content in the waste, the recovery of the waste management system, the substitutability of the recycled plastic against its virgin counterpart and the market response. 22 This scoring system could be useful for lifecycle assessment (LCA) and more fundamental studies rather than being a decision tool for recycling facilities due to the need for data specific to each plastic assessed, such as the plastic content in the waste, its recovery and current market response, which may not be readily and easily accessible.…”

“…However, the 'substitutability' factor could be applied to recycled plastics for bitumen/asphalt modification following the same principles in the eight-criterion ranking tool specifically developed for the bitumen/asphalt sector. 23 Such tools could therefore be adopted by plastic recycling facilities to regularly check the quality of the recycled plastic they produce and the suitability for road applications.…”

“…1(c)) and therefore limit their use as bitumen modifiers if their viscosity is too high. A recent study assessed the MFI of 31 different sources of recycled plastics and demonstrated that the MFI of PE‐based recycled plastics varied from 0.06 to 10.20 g (10 min) −1 at 19 °C, whereas the MFI values of virgin LLDPE, LDPE and HDPE ranged between 2.03, 1.69 and 0.05 g (10 min) −1 , respectively 23 . The presence of fillers and/or infrequent inclusion of PP in the PE‐based recycled plastics could explain the variability between the MFI values of the different plastic sources (Figs 1(a) and (b)).…”

“…A tool supporting the selection of recycled plastic sources for bitumen/asphalt modification would be useful for recyclers to develop ‘road‐grade’ plastics with dedicated production lines for the bitumen/asphalt industry. One recent study presented a ranking tool based on eight criteria applied to 31 different sources of recycled plastics to predict which types of recycled plastic are more suitable for bitumen/asphalt modification and highlighted that, overall, LDPE/LLDPE‐based plastics were the most suitable, whereas comingled plastics (three or more plastic streams) were the least appropriate, although still usable 23 . The composition and chemical and physical properties of the recycled plastics were used to rank the recycled plastics against virgin plastics and EVA, a polymer commonly used for bitumen modification, which ranked higher than all the other plastic sources 23 .…”