Research: Disposable Masks Create Durable Concrete
Known to be a carbon-intensive process, the production of cement is reported to be responsible for as much as 8% of the world’s carbon emissions. Another environmental problem the world is seeing because of the COVID-19 pandemic is improper disposal of single-use masks.
To tackle both issues, researchers from Washington State University have recently demonstrated how old masks could be utilized in cement mixtures to create stronger, more durable concrete.
“These waste masks actually could be a valuable commodity if you process them properly,” said Xianming Shi, professor and interim chair of the Department of Civil and Environmental Engineering and the corresponding author on 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?’”
According to WSU, when processed properly, the microfibers from single-use masks could be used to strengthen concrete and reduce the amount of cement needed. Microfibers are already sometimes added to cement concrete to strengthen it, but they’re expensive.
By recycling the masks, which are made from polypropylene or polyester fabric, the fibers could be useful for the concrete industry and promote cost savings as well. In addition, the recycling of single-use face masks would also prevent damage to the environment if not disposed of properly.
“This work showcases one technology to divert the used masks from the waste stream to a high-value application,” Shi said.
For their research, the team developed a process to fabricate tiny mask fibers, ranging from five to 30 millimeters in length, and then added them to cement concrete to strengthen it and to prevent its cracking. Metal and cotton loops were removed from the masks for the study but were cut and incorporated into ordinary Portland cement.
The microfibers from the majority if the mask material were then mixed into a solution of graphene oxide before adding the mixture to cement paste.
“The graphene oxide provides ultrathin layers that strongly adhere to the fiber surfaces. Such mask microfibers absorb or dissipate the fracture energy that would contribute to tiny cracks in the concrete,” wrote WSU. “Without the fibers, these microscopic cracks would eventually lead to wider cracks and the material’s failure.”
Moving forward, researchers are planning to conduct 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 deicing chemicals used on roadways. The team also intends to apply the technology to the recycling of other polymer materials.
This study has since been published in the journal Materials Letters. Zhipeng Li, a graduate student in WSU’s Department of Civil and Environmental Engineering, led the work, which was funded through the U.S. Department of Transportation’s National Center for Transportation Infrastructure Durability and Life Extension.
Similar Research Studies
In February 2021, researchers from RMIT University have recently developed a recycling solution for one item generating a rather large amount of pandemic waste: single-use face masks.
The first study of its kind to investigate potential civil construction applications of disposable surgical face masks, RMIT researchers claim the combination of shredded single-use face masks and processed building rubble meet civil engineering safety standards, and that the masks add stiffness and strength to the final product.
Professor Jie Li lead the RMIT School of Engineering research team, which focuses on recycling and reusing waste materials for civil construction.
The combined materials are envisioned to be utilized for base layers of roads and pavements. With an estimated 6.8 billion disposable face masks being used across the globe each day, the study certainly has a lot of potential material to work with.
Made up of four layers, the roads consist of a subgrade, base, subbase and are topped with asphalt. The processed building rubble—also known as recycled concrete aggregate—can be used for all three base layers as the material successfully withstands heavy pressure. However, in adding the shredded face mask material, researchers found that in addition to strengthening the material, the process addresses both PPE disposal and construction waste.
By combining 1% recycled face masks and 99% process building rubble, the team found an optimal mixture that delivers on strength and maintains cohesion between the two materials. Researchers also tested the mixture against stress, acid and water resistance, as well as strength, deformation and dynamic properties, which met all relevant civil engineering specifications.
RMIT also noted, that while the study used a small amount of unused surgical face masks, other research has investigated effective methods for disinfecting and sterilizing used masks. Most notable, a comprehensive review on the disinfection or sterilization of masks found that 99.9% of viruses could be killed off by spraying the masks with an antiseptic solution and microwaving for one minute.
In addition to working with materials for road construction, RMIT researchers were also looking at using the shredded masks for concrete. Li reports that his team was inspired to look at other uses for the masks after seeing so many be littered in the streets.
The study, “Repurposing of COVID-19 Single-Use Face Masks for Pavements Base/Subbase” has since been published in the journal Science of the Total Environment. Co-authors of the study include RMIT Indigenous Pre-Doctoral Research Fellow Shannon Kilmartin-Lynch and Research Assistant Mahdi Boroujeni.