The fiber from old tires can be used to fortify concrete against fire damage, according to research from the University of Sheffield, U.K.

By removing the fibers commonly built into tires to improve their performance, a team of researchers from the university demonstrated that mixing those fibers with concrete resulted in a reduction of the explosive spalling — the breaking off of concrete surface layers — that often accompanies exposure to the intense heat of fire. Because the tire fibers melt when exposed to fire, a series of tiny channels are left behind that enable moisture trapped within the concrete to escape instead of eventually exploding.

In addition to alleviating the pressure within concrete, the tire fibers also protect the steel reinforcements that run through concrete structures. Steel reinforcements typically respond to extreme heat by quickly weakening, increasing the odds that the structure will collapse.

A number of modern-day structures have been constructed with concrete reinforced with manmade polypropylene (PP) fibers that have the same effect as the tire fiber and concrete mixture, protecting concrete structures from damage or collapse following a fire. But the research from Sheffield University is the first to demonstrate that fibers can be reclaimed from old tires and not manufactured from raw materials.

"We've shown that these recycled fibres do an equivalent job to 'virgin' PP fibres which require lots of energy and resources to produce," explained lead author Dr. Shan-Shan Huang, in the Department of Civil and Structural Engineering at the University of Sheffield.

"Using waste materials in this way is less expensive, and better for the planet."

In collaboration with Sheffield-based innovative solutions company TwinCon, the university has also been creating different techniques for untangling the fiber from the tire rubber for the purpose of distributing the fiber evenly throughout the concrete mixture. Plans are currently underway to test the material with different fiber and concrete ratios.

In addition to construction, discarded tires are being repurposed for use in applications like light rail construction, septic system construction, landfill design, and construction and road construction. For more on how discarded tires are being repurposed, read The Civil Engineer’s Love Affair with Tire Scrap on Engineering360.

The University of Sheffield study is published in the journal Fire Technology.

To contact the author of this article, email mdonlon@globalspec.com