Multiscale evaluation of the effect of recycled polymers on the long-term performance of bituminous materials

The use of recycled polymers as bitumen modifiers contributes to extending their application at a competitive cost being also a more sustainable solution. However, despite several studies proving their benefits in asphalt mixtures, their use is not yet widespread. Hence, this research explored the long-term performance of bituminous materials made with two of the most common recycled polymers (household polyethylene and a combination of polyethylene and crumb rubber). To achieve this, fatigue cracking, ageing and environmental effects (i.e. moisture and temperature susceptibility) were evaluated at the most significant scales (microstructure, bitumen, mortar and asphalt mixture) through: Atomic Force Microscopy (AFM), Multiple Stress Creep and Recovery (MSCR), Dynamic Mechanical Analysis (DMA) and UGR-FACT tests. Results proved that recycled polymers (especially for LDPE and Crumb Rubber combination) represent an improvement in durability at the binder level that thrives at all the scale levels tested thus providing greater confidence to extend its use.