PAVING THE WAY
Recycled masks may improve roads, help environment
They end up in the trash. They end up in waterways. They end up on the ground in parks, at the beach or in yards. Perhaps soon, those disposable medical masks that have been such a big part of the COVID-19 pandemic may end up reinforcing the asphalt used in road construction.
Faculty and students in the East Carolina University Department of Construction Management have been working with S.T. Wooten and the N.C. Department of Transportation this spring and summer to determine the possibility of using the polymer fibers in recycled masks in hot mix asphalt used to pave roads.
The hope is that the addition of the recycled masks will help the asphalt resist rutting — the permanent deformation of pavement that can occur as vehicles drive on the same areas on roadways over and over again.
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Dr. George Wang, chair of the Department of Construction Management and one of those involved in the effort, said the single-use masks are being disposed of in landfills and dumpsites, but others are littering waterways and other public spaces, creating environmental issues. He cites studies — including one led by Portuguese researcher Joana Prata that estimates 129 billion face masks were used monthly throughout the world during the pandemic — that illustrate the problem.
“The coronavirus pandemic has not only created a global health crisis, but it is also now threatening the environment,” Wang said. “Even if disposed of correctly, single-use face masks made of polypropylene have a lifespan of a couple hundred years before breaking down in landfills. To mitigate these environmental challenges, we as researchers in construction in higher education have obligations to explore possible ways to reduce, recycle and reuse the disposed single-use COVID-19 face masks.”
Ruts like these on a road in Greenville can create driving hazards, especially in rain. ECU researchers hope to show that recycled medical masks can reinforce asphalt and reduce rutting. (Contributed photo)
The process begins by simply shredding the masks. The material is then added to the hot mix asphalt by .25% to 1.5% of the total weight. With paving conducted at up to 300 degrees, the plastic in the masks becomes a fluid and acts as a binding agent that hardens and stiffens as it cools. This could help reduce road rutting, which is caused by traffic volume, tire pressure and axial load and often emerges in the first few years after a road is paved.
“Rutting is the major distress of asphalt pavement and happens on some major intersections along the wheel path,” Wang said. “It can cause accidents with water ponding in the rut and in wintertime when water in the rut freezes.”
So far results of testing in the N.C. Department of Transportation’s Asphalt Pavement Analyzer appear favorable, with the sample asphalt exhibiting “excellent to very good resistance to permanent deformation,” according to the report. Wang said that while the state allows a maximum rut depth of 11.5 millimeters for local roads and 4.5 millimeters for interstate highway pavement, testing of various mixtures with the recycled masks show a rut depth range of .9 to 3.2 millimeters.
“With the increase in content of fiber, the rut decreases,” Wang said. “That means that this mix is designed for local roads, and because of the fiber addition, it can be used as higher grade road pavement.”
Md. Hasibul Hasan Rahat shreds surgical masks as part of research to determine if masks from the pandemic can be used as filler with asphalt. (Photo by Cliff Hollis)
Wang, associate professor Dr. Carol Massarra, teaching assistant professor Dr. Jodi Farrington, teaching instructor Chelsea Buckhalter and graduate student Md. Hasibul Hasan Rahat are conducting the research.
Rahat had the task of shredding all the masks used in the tests and understands the importance the research can have.
“It is an environmentally friendly and economically innovative research idea that will help to reduce solid wastes and enhance the longevity of transportation infrastructure,” he said. “If we become successful in this research, it will have a huge impact not only in the U.S. environment and transportation infrastructure, but also all over the world will get the benefits of the research application.”
Wang said researchers would continue to work with the Department of Transportation and S.T. Wooten to conduct more extensive testing and possibly funded research on the use of mask and similar nonstructural fibers in asphalt. They are also working on publishing the results of the initial testing.