In a laboratory in Melbourne, concrete cylinders are being subjected to extreme pressure.
The cylinders may look like ordinary concrete, but they are not. They are made with polyester fibres extracted from hi vis clothing worn by factory and construction workers.
Around 11,000 tonnes of reflective safety vests end up in landfill every year.
It's one reason engineers at Victoria University (VU) have spent the past year developing new uses for discarded items.
Melbourne researchers have discovered a method to reuse coffee cups and hi vis waste to create concrete. Source: SBS / Scott Cardwell
Reflective safety vests repurposed into concrete
Every year, Australians throw out 11,000 tonnes of textile waste in the form of uniforms, including hi vis vests, according to Sustainability Victoria (SV).
The fluorescent materials and reflective strips on the vests fade over time and need to be replaced every six months.
VU associate professor Malindu Sandanayake, who leads the project, said: "High Vis vests only last for around 25 washes."
"That means many used vests end up in landfills. So, we wanted to find an effective solution, and one solution was a cement replacement material in concrete."
Social enterprise Assembled Threads helped source the uniforms for this research, which is backed by SV.
Reflective safety vests were chosen for the project because their threads are very durable.
"The vests contain synthetic fibres that can act as a reinforcing agent within the concrete," Sandanayake said.
"It bonds the materials together and delays the spoiling process.
"Also, durable textile fibres enhance the fire properties within the concrete panel."
Australians discard 11,000 tonnes of textile waste each year, including high-visibility vests and uniforms, according to Sustainability Victoria. Source: SBS / Scott Cardwell
Cement, a key ingredient in concrete, is usually made from limestone and clay.
By reusing vest fibres, it is possible to conserve these natural resources while diverting waste from landfills, which helps reduce greenhouse gas emissions.
"Producing cement is a bit like making cars; it generates a huge amount of carbon emissions — in fact, around 8 per cent of the total global carbon production," Sandanayake said.
The new concrete has been used to construct a 20m path through the grounds of the Mahamevnawa Buddhist Meditation Monastery in Melbourne. Source: SBS / Scott Cardwell
Monks at the monastery are proud to be involved in the trial.
"The environment is directly helping our happiness and especially our health. So, if we are really trying to protect our environment, that means we are really trying to help every single living being in the world," Sasana Bodhi Thero, a monk, said.
In fact, he couldn't be more pleased with the result.
Monk Sasana Bodhi Thero from Mahamevnawa Buddhist Monastery in Melbourne says the monastery is proud to be involved in the trial. Source: SBS / Scott Cardwell
"We are so happy because when we walk on it, it feels the same."
Monastery volunteer Amila Goonaratne said the monks share the path with the local community.
"In Buddhist teachings, we learned that you have to treat all living beings with loving kindness. And so, if you care about all living beings and if you have loving kindness, you care about the environment. So being sustainable is definitely a part of that."
The concrete was also tested in a storage compound on a major construction site. Both trials delivered positive results.
Lead researcher Malindu Sandanayake says the new concrete showed superior durability and performed well in fire testing during trials. Source: SBS / Scott Cardwell
"And it is almost comparable with traditional concrete mix. It had superior durability results, plus in terms of fire testing, it performed really well.
"So, we believe that the presence of these textile fibres enhances the fire properties within the concrete panel. So, this could be a good fireproof concrete material for future use."
Turning spent coffee into concrete
Vest fibres are not the only waste material being turned into sustainable concrete. Researchers at Melbourne's RMIT University are working with spent coffee grounds.
According to Agrifutures Australia, Australians consume more than six billion cups of coffee annually, contributing to a coffee bean market worth around $1 billion.
That creates a lot of coffee waste.
RMIT researchers recently poured concrete made with coffee grounds to create a new footpath in Gisborne in the Macedon Ranges, about 54km north-west of Melbourne.
In the lab, coffee grounds are converted into biochar to replace sand — another key ingredient in concrete — which is becoming increasingly scarce.
Rajeev Roychand, lead inventor and research fellow, said: "To create biochar, we roast spent coffee grounds in a pyrolysis unit."
"Roasting is basically the absence of oxygen. So after we roast at 350C, out comes black coloured coffee biochar."
Roychand said results from a previous footpath trial showed a 30 per cent increase in the concrete strength. Researchers now hope to develop commercial applications.
Clean Up Australia chair Pip Kiernan says a lot of improvement is needed in reducing waste sent to landfills and in recovering and reusing non-food items. Source: Supplied / Clean Up Australia
Are there any benefits of reusing waste?
Clean Up Australia Chair Pip Kiernan said reusing products in this way reduces demand for raw materials.
"Australia lags the world in developing a circular economy," she said.
"Compared with other countries, Australia reuses around 4 per cent while the rest of the world sits at around 8 per cent.
"So, there is a lot of improvement needed when it comes to sending less waste to landfills and recovering and reusing non-food items."
Lead researcher Malindu Sandanayake says VU researchers have also used end-of-life concrete as a substitute for sand and gravel in the creation of new concrete. Source: SBS / Scott Cardwell
The team is working on ways to incorporate even higher proportions of waste into concrete. But Sandanayake said they need vast amounts of reflective safety vests to achieve commercial production.
