Crumb rubber from end-of-life tyres recycled into concrete

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A novel approach to rubber recycling could see end-of-life tyres repurposed into concrete for residential constructions, claim researchers in Australia.

crumb rubber
(Image: Berger Team, Pixabay)

New research from the University of South Australia, in collaboration with RMIT University, demonstrated that crumb rubber concrete is a safe, green alternative for residential construction in Australia.

Lead researcher, UniSA’s Professor Julie Millssaid the research is the first to practically demonstrate and construct the new crumb rubber concrete mix in the field.

Globally, approximately 1.5 billion vehicle tyres are discarded annually but less than one per cent of these are reused, with the rest being unaccounted for or dumped in landfills. In Australia alone about 51 million tyres end up in landfills, stockpiles or dumped on mine sites.

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“Rubber tyres are not biodegradable and lead to unstable landfills, breeding grounds for mosquitoes from trapped water, polluted surfaces and toxic groundwater. They [also] pose a significant risk for toxic fires,” said co-researcher Dr Osama Youssf. “Such continuous waste production and disposal is entirely unsustainable, which is why we have been investigating alternative recycling options.”

He added: “This research investigated the design and processing of various crumb rubber concrete mixes for use in residential constructions, assessing its constructability, bond strength, durability, and flexural strength.

“We found that reinforced crumb rubber concrete - with up to 20 per cent sand replacement by volume - is superior to conventional concrete in some ways, with higher impact resistance, toughness and ductility, a higher damping ratio, better thermal and acoustic insulation, and a lighter weight.

“With respect to pumping, screeding, or finishing the concrete surface using a power trowel, contractors also reported no difference between using the crumb rubber concrete and conventional concrete, saying that the crumb rubber mix actually required less physical effort across all aspects.

“Additionally, the ready-mix cement companies reported no concerns relating to concrete batching, delivery or mixing, and said that the wash out of the concrete truck mixer was far easier.”

As part of their research two residential slabs (one with crumb rubber concrete and the other with conventional concrete) were poured at the University of South Australia’s Mawson Lakes campus in October 2018. The slabs have been monitored for over two years and the crumb rubber concrete slab continues to perform well. The team’s findings are published in Structures.

“This is an exciting development for both the recycling and construction industry,” said co-researcher Prof Yan Zhuge. “The results clearly show that crumb rubber cement is a viable and promising alternative to conventional concrete in the residential concrete market.”