WPB reports that scientists at the University of Missouri are piloting a strongly viable road building technique—mixing post-consumer polyethylene with asphalt mixes. Not only is this process the solution to the issue of rapidly rising bitumen costs, the conventional petroleum-based binder, but it offers substantial performance gain and environmental benefits, too.
Across North America, millions of road miles, airport runways, and parking lots are surfaced with asphalt—a composite of mineral aggregate materials such as crushed stone, gravel, and sand bound together by bitumen. Although aggregates make up some 95% of the mixture in volume terms, bitumen is the by far most expensive ingredient, commonly costing upwards of $600–700 per ton compared to aggregates at the order of $20 per ton. Even substituting part of the binder with a more affordable material would yield handsome economies without cutting back on quality.
In pursuit of such a replacement, the Missouri research team turned to polyethylene, the world's most readily available plastic. It goes into products ranging from packaging film and synthetic fibers but has large amounts that go unrecovered and instead end up in landfills because of processing limitations. By employing up to 40% polyethylene in asphalt blends, the researchers reduced binder cost, increased strength, and enhanced sustainability objectives.
Methods and Application
There are two prevailing ways of altering asphalt: the wet process, in which additives are incorporated into the binder before blending it with aggregates, and the dry process, in which modifiers are mixed with aggregates at production stage. The University of Missouri group favored the dry process, and through this, granulated or powdered polyethylene could be fed directly into the mixing drum. This streamlined production and avoided the lead times and higher costs usually associated with pre-prepared modified binders.
Testing in the field began in 2021 on a thin overlay to the south of the university campus. Four consecutive winters later, the test asphalt performed well. More testing was done on nine test sections on Interstate 55, between New Orleans and Chicago, and Kansas City neighborhood streets—each showing good resistance to cracking, rutting, and water damage.
Shifting to Runway Standards
The next challenge for the research team was to adapt the technology to fit the stringent requirements of airport runways, where safety standards exceed those on highways. Runway surfaces must not only support heavy loads without deforming but also minimize the risk of Foreign Object Debris (FOD), which can perforate engines or fuselages of aircraft. Collaborating with the Federal Aviation Administration, the team is searching for possible test sites in Missouri, Iowa, and Illinois and conducting lab tests to adjust the blend for airfield performance.
For runways, asphalt needs to be resistant to rutting during hot conditions but also flexible in cold temperatures so that it won't crack—a delicate balance necessary for the avoidance of FOD and safe aircraft operation. Smooth, stable pavement also lessens the risk of hydroplaning and enhances braking performance upon landing.
Addressing Environmental Concerns
In addition to mechanical performance, the researchers also examined the environmental impact. Experiments in the lab confirmed that encapsulation of polyethylene within asphalt binder does not support significant microplastic release, and testing showed no measurable PFAS (per- and polyfluoroalkyl substances) in the recycled material. Plastic waste is sealed in the process, deterring leach damage and the extension of the material's service life.
This project, in collaboration between the Mizzou Asphalt Pavement and Innovation Lab and the FAA, is a practical step toward more sustainable infrastructure. Recycling hard-to-recycle plastics into a structural element, the project eliminates waste while making the transportation nodes even stronger. With additional research and field testing, this technique can revolutionize the manufacture of asphalt for roadways and runways as well—uniting cost-effectiveness, environmental responsibility, and engineering functionality in a single solution.
By Bitumenmag
Bitumen, Asphalt, Road, Pavement
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