Effects of marine microplastics on the mechanical performance of bituminous binder for road asphalt pavements

Microplastics, MPs, represent a apprehension as their accumulation causes irreversible damage to the marine environment and wildlife and consequently in the food chain. At the same time, it is well recognized that MPs can outstandingly improve the road performance of bitumen. In this regard, encapsulating marine MPs in bitumen can indeed both enhance the performance of bitumen and encourage their recycling. Therefore, the goal of this study is to investigate the feasibility of marine MPs as fillers or modifier in bitumen. Three different MPs compositions and two different dosage (3 and 6% wt. of bitumen) were analyzed, for a total of six solutions and compared with 1) asphalt mastics containing traditional limestone powder and 2) modified bitumen (PMB). The obtained asphalt mastics or modified bitumen were characterized in terms of empirical and rheological analyses. It was found that in the presence of 6% MPs, the softening points of neat B50/70 bitumen (B50/70) can be increased by more than 6.1°C, and the penetration can be reduced by more than 8.0 dmm. B50/70 and showed a significant improvement in the elasticity and stiffness since the phase angle is reduced while the complex shear modulus is increased. Marine MPs are innovatively employed to achieve modification of flexible road binders corresponding to significative reductions of heavy metals concentration up to 85%. Therefore, a recycling strategy of marine MPs is developed, offering a new solution for sustainability in the field of road engineering.