Feb. 21 (UPI) -- Engineers at the University of Sheffield have developed a technique for extracting fibers from old tires and adding them to concrete mix, improving the concrete's resistance to fire.
Under pressure from intense heat, concrete violently sheds its surface layers -- an act known as spalling. When concrete spalls, the structural integrity of a building or bridge can be compromised.
Most large building and infrastructure projects use concrete mix bolstered with human-made polypropylene fibers. The fibers help prevent spalling.
Sheffield researchers found a more eco-friendly method for fireproofing concrete. Instead of relying on fibers produced using raw materials, scientists developed a new technique for extracting fibers from old tires.
"Using waste materials in this way is less expensive, and better for the planet," Shan-Shan Huang, senior lecturer in structural engineering at Sheffield, said in a news release.
Concrete spalls because liquid in the material expands and causes pressure to mount until the concrete's outer layers fracture and explode. When fibers are embedded, they melt from the intense heat and create tiny channels through which the trapped moisture can escape.
"Because the fibers are so small, they don't affect the strength or the stiffness of the concrete," said Huang. "Their only job is to melt when heat becomes intense. Concrete is a brittle material, so will break out relatively easily without having these fibers help reducing the pressure within the concrete."
Tire makers use fibers to reinforce the strength of rubber and improve the endurance and performance of tires. Huang and her colleagues developed a method for extracting these fibers, untangling them into strands and mixing them gently into concrete mix.
Scientists detailed their new technique this week in the journal Fire Technology.
Sheffield researchers are currently working with Twincon, a local construction company, to test the fireproofing benefits of different tire fiber concentrations in a variety of concrete types.