With increasing demands for longer-lasting roads and less construction waste, researchers at Pennsylvania State University found that asphalt made with recycled plastic outperformed regular asphalt in lab tests and released fewer plastic-like particles under simulated road conditions.

The study looked at asphalt mixed with recycled low-density polyethylene (LDPE), which is often used in packaging. The results suggest that stronger pavement could help reduce particle release as roads deteriorate. However, researchers cautioned that real-world testing is needed to confirm these results.

Microplastics are tiny particles less than 0.2 inches (5 millimeters) found in water, soil, and air. Roads can contribute to environmental pollution through tire wear and pavement breaking down. Construction materials with plastic might also release particles as they get older.

“Our goal was to understand whether asphalt pavement containing recycled plastic could release microplastic particles as it is damaged over time,” said Shihui Shen, distinguished professor of rail transportation engineering at Penn State Altoona and corresponding author on the paper.

“That environmental question has received much less attention than the engineering performance of the pavement.”

To make the recycled-plastic asphalt, the researchers mixed shredded LDPE with crushed stone and old asphalt pavement, then added the binder. They compared this mix to regular asphalt to see how each performed under simulated road conditions.

The team put asphalt samples through two lab tests that mimic the stresses roads face. In the Hamburg Wheel Tracking Test, steel wheels rolled over samples in hot water again and again, simulating traffic, heat, and moisture.

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