The researchers experimented with different proportions of recycled tire fibers and other materials used in concrete—cement, sand and water—before finding a working mix, which includes 0.35 percent tire fibers, according to researcher Obinna Onuaguluchi, a postdoctoral fellow in civil engineering at UBC.
Asphalt roads that incorporate rubber "crumbs" from shredded tires exist in the U.S., Germany, Spain, Brazil and China. But using the polymer fibers from tires can potentially improve the resilience of concrete and extend its lifespan.
"Our lab tests showed that fiber-reinforced concrete reduces crack formation by more than 90 percent compared to regular concrete," says Onuaguluchi. "Concrete structures tend to develop cracks over time, but the polymer fibers are bridging the cracks as they form, helping protect the structure and making it last longer."
UBC civil engineering professor Nemkumar Banthia, who supervised the work, says the environmental and industrial impact of the research is crucial. Up to 3 billion tires are produced around the world every year, generating close to 6 billion pounds of fiber when recycled.
"Most scrap tires are destined for landfill. Adding the fiber to concrete could shrink the tire industry's carbon footprint and also reduce the construction industry's emissions, since cement is a major source of greenhouse gases," says Banthia.
The new concrete was used to resurface the steps in front of the McMillan building on UBC's campus in May. Banthia's team is tracking its performance using sensors embedded in the concrete, looking at development of strain, cracking and other factors. So far, the results support laboratory testing that showed it can significantly reduce cracking.