With more than 1500 billion disposable face masks in use annually as a result of the COVID-19 pandemic, researchers are analysing their waste to potentially increase strength and durability in concrete.
The ubiquitous mask is made of polypropylene (polyester) fabric made up of microfibres which can absorb or dissipate fracture energy, reducing micro-cracking with concrete.
Researchers at Washington State University (WSU) in the US have tested the masks’ waste product by removing the cotton loops and metal, cut them up, and reduced them to fibres of 5-30 mm in length with a diameter of 20-40 micrometres.
Some of these were mixed into a solution of graphene oxide that provides an ultra-thin layer which strongly adheres to the fibres’ surfaces to aid in the waste-mask mix adhering to the cement mix. The researchers then incorporated them into Portland cement and tested for compressive and splitting tensile strength.
While some tweaking of the mix is required, the results are promising, showing splitting tensile strength increase of 33% with the waste-mask mix and 47% with the waste-mask mix and graphene oxide after 28 days.
Corresponding author, Professor Xianming Shi of WSU’s Department of Civil and Environmental Engineering, said disposed masks represent a valuable commodity if they could be processed properly.
“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?”
The researchers are looking to apply the technology to focus on other polymer materials such as discarded clothing. The research paper has been published in the journal Material Letters.