With the ubiquitous single-use face masks now presenting an environmental problem, researchers have demonstrated the idea of incorporating old masks into a cement mixture to create stronger, more durable concrete.

In a paper in Materials Letters, a research team from Washington State University (WSU) showed that a mixture containing mask materials was 47% stronger than commonly used cement after a month of curing.

“These waste masks actually could be a valuable commodity if you process them properly,” said Xianming Shi, professor and interim chair in the Department of Civil and Environmental Engineering at WSU and corresponding author of the paper. “I’m always looking out for waste streams, and my first reaction is ‘How do I turn that into something usable in concrete or asphalt?’”

Production of cement is a carbon-intensive process, responsible for as much as 8% of carbon emissions worldwide. Microfibers are already sometimes added to cement concrete to strengthen it, but they’re expensive. Microfiber-reinforced concrete can potentially reduce the amount of cement needed for a project or make the concrete last longer, saving carbon emissions as well as money for builders and owners.

Made of a polypropylene or polyester fabric where it contacts the skin and an ultra-fine polypropylene fiber for the filtering layers, medical face masks have fibers that can be useful for the concrete industry. If they are not reused, disposable masks can remain in the environment for decades and pose a risk for the ecosystem.

“This work showcases one technology to divert the used masks from the waste stream to a high-value application,” Shi said.

In their proof-of-concept work, the researchers developed a process for fabricating tiny mask fibers, ranging from 5mm to 30mm in length, and then added them to cement concrete to strengthen it and prevent its cracking. For testing, they removed the metal and cotton loops from the masks, cut them up and incorporated them into ordinary Portland cement, the most common type of cement used around the world, and the basic ingredient for concrete, mortar and grout.

They mixed the mask microfibers into a solution of graphene oxide before adding the mixture to the cement paste. The graphene oxide provides ultrathin layers that strongly adhere to the fiber surfaces. The mask microfibers can absorb or dissipate the fracture energy that would normally contribute to the growth of tiny cracks in the concrete. Without the fibers, these microscopic cracks would eventually lead to wider cracks and the material’s failure.

The researchers are conducting more studies to test their idea that the graphene-oxide-treated microfibers could also improve the durability of concrete, and protect it from frost damage and from deicing chemicals that are used on roadways. They also envision applying this technology to the recycling of other polymer materials, such as discarded clothing, to incentivize the collection of such waste.

This story is adapted from material from Washington State University, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.