The use of vast quantities of disposable face masks has solved one problem, but inadvertently created another: waste. This has led researchers from RMIT University in Melbourne, Australia, to find a solution that turns used masks from trash into roads.

With the increase in use of personal protective equipment (PPE) during the current pandemic, an estimated 6.8 billion disposable face masks are used each day worldwide. The RMIT study showed that 93 tons of waste (about 3 million masks) can be diverted from landfills by using it to make one kilometer of a two-lane road.A sample of the recycled road-making material, which blends shredded single-use face masks with processed building rubble. Source: RMIT University

All four layers that make up a road — subgrade, base, sub-base and asphalt — must be strong and flexible enough to hold up under the pressures of heavy vehicles. The researchers developed a new material by combining shredded single-use face masks and processed building rubble, also known as recycled concrete aggregate (RCA).

Their analysis showed that the face masks added both stiffness and strength to the final product. The study found the mixture of 1% shredded face masks to 99% RCA is optimal for strength and cohesion between the materials. The mixture successfully meets all relevant civil engineering specifications in tests for stress, acid and water resistance, strength, deformation and dynamic properties.

While RCA can be used on its own for the base layers, the value of adding the shredded face masks addresses the challenges of both PPE disposal and construction waste. Construction waste, including from demolition and renovation, makes up about half of the world’s waste. In Australia, about 3.15 million tons of RCA is stockpiled each year.

The study was conducted with unused surgical face masks; however, other research has investigated methods for effectively disinfecting and sterilizing used masks. One comprehensive review found 99.9% of viruses can be killed by spraying the masks with an antiseptic solution and then microwaving them for one minute.

"This initial study looked at the feasibility of recycling single-use face masks into roads and we were thrilled to find it not only works, but also delivers real engineering benefits," first author Dr. Mohammad Saberian said. "We hope this opens the door for further research, to work through ways of managing health and safety risks at scale and investigate whether other types of PPE would also be suitable for recycling."

Professor Jie Li, who leads the RMIT School of Engineering research team that focuses on recycling and reusing waste materials for civil construction, explained that the inspiration for this project came from team members who saw face masks littering the streets. "We know that even if these masks are disposed of properly, they will go to a landfill or they'll be incinerated," he said. "The COVID-19 pandemic has not only created a global health and economic crisis but has also had dramatic effects on the environment. If we can bring circular economy thinking to this massive waste problem, we can develop the smart and sustainable solutions we need."

The study is published in the journal Science of the Total Environment.