Concrete made with old tires proves itself in real-world setting

Concrete made with old tires proves itself in real-world setting
Crumb rubber concrete made by grinding down discarded tires has stood up well in real-world testing
Crumb rubber concrete made by grinding down discarded tires has stood up well in real-world testing
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Crumb rubber concrete made by grinding down discarded tires has stood up well in real-world testing
Crumb rubber concrete made by grinding down discarded tires has stood up well in real-world testing

With a notoriously large carbon footprint, concrete is a prime target for researchers developing greener materials for the future of construction. A number of studies have shown how old rubber tires can be used to make versions that are stronger, more heat-resistant and flexible enough for use as a road material. A new study has assessed its value in real-world settings by using concrete containing old tires as a residential slab and monitoring its performance over several years, where it outshone conventional concrete in a number of ways.

The type of concrete at the center of this study is known as crumb rubber concrete, and its production involves grinding rubber tire down into crumbs of a similar consistency to sand. These crumbs can then be used to replace a certain proportion of the sand typically mixed in with the cement, water and other ingredients to form concrete, lessening the reliance on the natural material and giving the discarded rubber a second life.

Scientists at the University of South Australia and Melbourne's RMIT University have sought to take this material from the "lab to the slab," noting that while it has shown a lot of promise in laboratory testing, its reliability in real-world construction requires further exploration.

To investigate its practical application in residential settings, the scientists poured two crumb rubber-reinforced concrete slabs at the University of South Australia campus in 2018, along with two conventional concrete slabs. These formed the entrances to a civil engineering laboratory that sees a lot of foot traffic, with the team closely monitoring the materials' performance over time.

“We found that reinforced crumb rubber concrete (with up to 20 percent 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," said study author Dr Osama Youssf. “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."

Factors like impact resistance and toughness bode well for the longevity of the concrete, which is a key focus for scientists working in this area. Concrete is incredibly carbon-intensive to make, so when it begins to crack, degrade or fail and structures need to be replaced, it places yet more strain on the environment. Making more durable forms of it while putting old, non-biodegradable tires to use could therefore be beneficial on a couple of fronts.

“The results clearly show that crumb rubber cement is a viable and promising alternative to conventional concrete in the residential concrete market,” said study author Professor Yan Zhuge. “We strongly recommend that the concrete industry considers crumb rubber concrete as a sustainable alternative to conventional concrete in reinforced residential constructions in Australia.”

The research was published in the journal Structures.

Source: University of South Australia

The French have been recycling tyres to build roads for years. Longlasting and quiet which makes them especially useful on motorway surfaces close to people's homes
An excellent way to re-purpose those millions of used tires! Can the steel or Kevlar belt used in them also be salvaged ar repurposed?
I think this is absolutely something that needs to be utilized in new construction in the United States, especially construction used for outdoor environments. This could also be integrated in cement block and cement bricks used in sidewalks, driveway construction and exterior hard scapes.
Willy Lee
Wishful Thinking. Slabs in this study saw Foot Traffic Only.
Other PCC Test Slabs outside "Transfer Stations" with heavy Truck Traffic didn't do to badly, Twenty-Five Years Ago, but garnered little interest.
Crumb Rubber use in Asphaltic Roadways has been pushed HEAVILY, for over Thirty Years, but they don't quite work well.
And Yes, the Steel Belts are quite a problem for the Crumb Rubber Recyclers.
This is a great idea for concrete making and usage, but not because of the carbon footprint of conventional concrete. We need more carbon dioxide in the atmosphere, which will help plants, trees, and crops grow better.
Dan Lewis
I wish all well.

'Outshone' struck me as an odd adjective for a road's performance.

WHERE are the photos?? Someone dropped the ball here.
We should have had 'Before' and 'Two years later' shots.

MAJOR doubts about how such a formulation might SAFELY benefit, and serious concerns about long term environmental effects as that stuff oxidizes, sheds chemicals, etc.

You've got 'rocks and rubber'.
If that system is applied to actual road surfaces that vehicles bear down on, the rocks are going to chew up the rubber.
If you've ever tried to glue your shoe sole back in place, you might see the similarity.

Most fail at the sole-gluing because bits of grit are left at the point of parting, and as the person walks in the repaired shoes, those bits of grit are 'chewing' on the rubber/glue. Rubber/glue doesn't last forever, chewed or not.
I wonder what the realistic lifespan of such a surface might be.

I'm hope this system IS indeed environmentally friendly and CAN be quickly and easily applied and repaired.
I'm pretty sure we need water-shedding/draining road surfaces, not those that might pool water.

This is a cool reuse of a material. I'd love to see it tested with a mechanical concrete road base, revolutionize the road paving business. MC can easily handle 80k+ trucks by itself, paved with a proper road deck above it would be like autobahn level roads!

Not sure why the steel bands would be a problem, recycled steel is always scooped up. This is a value add rather than a "problem" - just need the right tools for the job , steel is magnetic and easily separated.
And now a new use for waste plastic: Grind it up into sand size particles. No sorting required.
I rest my case!
What Dan Lewis makes a ton of since, I wonder how the French get around the issue.
Lamar Havard
I had my 40 ft. x 10 ft. x 4" thick driveway put in around 15 years ago, and it has plastic fibers in it instead of rebar...still looks great. I'm sure rubber would work just as well, or better.
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