A group of engineers at RMIT University has developed a technique to use disposable personal protective equipment (PPE) to strengthen concrete while providing an innovative way to reduce pandemic-generated waste like masks, gloves and surgical gowns.
RMIT PhD candidate Shannon Kilmartin-Lynch and his RMIT research colleagues saw an opportunity to create a circular economy for PPE items when they saw how many masks were discarded, littering the streets of Melbourne as a result of the COVID-19 pandemic.
The RMIT team is believed to be the first to investigate the feasibility of recycling face masks and adding them to asphalt, and then subsequently adding plastic gowns and gloves to strengthen concrete.
“We urgently need smart solutions for the ever-growing pile of COVID-19 generated waste – this challenge will remain even after the pandemic is over,” Kilmartin-Lynch said.
Since the start of the COVID-19 pandemic, an estimated 54,000 tonnes of PPE waste has been produced on average globally every day, and approximately 129 billion disposable face masks are used and discarded around the world every month.
“Right now, in Australia, medical PPE is either incinerated or sent to landfill. Some companies are producing biodegradable PPE but the disposal of most of it is still a huge issue.
“Disposable face masks are made of polypropylene which is a material that has been extensively researched in engineering applications with a focus on its high tensile strength and low cost of production. In our initial research we needed to determine that the fibrous nature of the masks didn’t weaken the polypropylene and we found that it was fine,” said Kilmartin-Lynch.
The team used the shredded face mask fibres as an additive to hot mix asphalt to enhance rutting resistance. Rutting is one of the major distresses of asphalt pavement. The fibres function as a binding agent to glue the aggregates and based on the results of the study, the modified mixes exhibited excellent resistance to permanent deformation.
The next step was to look at disposable isolation gowns that are a blend of polypropylene and polyethylene, and finally, the team used nitrile gloves as a concrete additive.
Based on the team’s analysis, the cement and the shredded isolation gowns formed an excellent bond, with no gap observed at the interface between the gowns and the cement matrix.
“Our research found that incorporating the right amount of shredded PPE could improve the strength and durability of concrete,” said Kilmartin-Lynch.
The studies published by the RMIT School of Engineering in the journals Case Studies in Construction Materials, Science of the Total Environment and Journal of Cleaner Production, found that shredded PPE could increase the strength of concrete by up to 22% and improve resistance to cracking.
In the three separate feasibility studies, disposable face masks, rubber gloves and isolation gowns were shredded and then incorporated into concrete at various volumes, between 0.1% and 0.25%.
- rubber gloves increased compressive strength by up to 22%
- isolation gowns increased resistance to bending stress by up to 21%, compressive strength by 15% and elasticity by 12%
- face masks increased compressive strength by up to 17%.
The RMIT School of Engineering team’s industry partner, Casafico, a building material manufacturer, is planning to use these research findings in a field project.
“We’ve also had several councils come forward to participate in the field trials which will focus on a one-kilometre stretch of road and 200 metres of footpath.
“There are several steps that need to be taken before this research can become a commercial reality. We’re looking at a five- to ten-year projection but are confident that this can really make a difference to the amount of PPE going to landfill or being incinerated,” he added.
One of the key hurdles that the RMIT team will need to overcome is the regulatory requirements that exist for the disposal of PPE.
“Right now, we can use expired PPE and PPE that has not been exposed to high infection but there are regulations that prevent the re-use of PPE which requires a certificate of destruction,” he said.
The next step for the group is to conduct field trials which will help them determine the optimal mix to meet the required standards for various concrete applications. Casafico is the only industry partner at this stage, but the group has partnerships with groups like NSW Ambulance and Ambulance Victoria who are providing PPE.
“The pandemic highlighted the amount of PPE that is used every day in healthcare settings from emergency departments to local GPs, but it’s also used in many other industries. We use gloves and masks ourselves in our concrete laboratory,” said Kilmartin-Lynch.
“Because the use of disposable PPE is widespread, the collection of it also creates a major challenge. We need to be able to cost-effectively collect it, but also protect the people who are collecting it from contamination.
“I’m motivated to make a difference. I have a young daughter and I want to ensure that we build a sustainable future for her and others to enjoy,” he said.
Learn more about the biggest sustainability strides in engineering at the Climate Smart Engineering conference. It’s on around the country on 22-23 November. Speakers include Dr Saul Griffith, IPCC author Kevin Hennessy and MCi Carbon COO Sophia Hamblin Wang. View the full program here.
