PULLMAN, WA — With single-use masks ubiquitous during the pandemic now presenting an environmental problem, researchers have demonstrated the idea of incorporating old masks into a cement mix to create stronger, more durable concrete.
In a paper published in the journal, Materials Lettersa research team from Washington State University showed that the mixture using mask materials was 47% stronger than commonly used cement after a month of curing.
“These waste masks could actually be a valuable commodity if you treat them properly,” said Xianming Shi, professor and acting director of the Department of Civil and Environmental Engineering and corresponding author of the paper. “I’m always on the lookout for waste streams, and my first reaction is ‘how do I turn this into something usable in concrete or asphalt? “”
Cement production is a carbon-intensive process, responsible for up to 8% of carbon emissions worldwide. Microfibers are already sometimes added to cement concrete to strengthen it, but they are expensive. Microfiber reinforced concrete can potentially reduce the amount of cement needed for a project or extend the life of concrete, saving carbon emissions as well as money for builders and homeowners.
Made of polypropylene or polyester fabric in contact with the skin and ultra-fine polypropylene fiber for the filter layers, medical masks have fibers that can be useful in the concrete industry. If not reused, disposable masks can remain in the environment for decades and pose a risk to the ecosystem.
“This work presents a technology to divert used masks from the waste stream to a high-value application,” Shi said.
In their proof-of-concept work, the researchers developed a process to make tiny mask fibers, ranging from five to 30 millimeters in length, then added them to cement concrete to strengthen it and prevent it from cracking. For their tests, they removed the metal and cotton loops from the masks, cut them out, and embedded them in regular Portland cement, the most commonly used type of cement in the world and the basic ingredient in concrete, mortar and grout.
They mixed the mask’s microfibers in a solution of graphene oxide before adding the mixture to the cement paste. Graphene oxide provides ultra-thin layers that adhere strongly to fiber surfaces. Such mask microfibers absorb or dissipate fracture energy that would contribute to tiny cracks in the concrete. Without the fibers, these microscopic cracks would eventually lead to larger cracks and material failure.
The researchers are conducting further studies to test their idea that graphene oxide-treated microfibers could also improve the durability of concrete and protect it from frost damage and de-icing chemicals used on roads. They also plan to apply this technology to the recycling of other polymeric materials, such as discarded clothing, to encourage the collection of such waste.
– This press release was originally published on the Washington State University website