University of British Columbia (UBC) engineers have used polymeric scrap tire fibers (STF) to develop a more resilient type of concrete that could be used for concrete structures such as buildings, roads, dams and bridges, while reducing landfill waste.
The researchers experimented with different proportions of STF and other materials used in concrete—cement, sand and water—before finding the optimal mix, which includes 0.35% tire fibers, according to researcher Obinna Onuaguluchi, a postdoctoral fellow in civil engineering at UBC. A paper on the work is published in the journal Materials and Structures.
Results of the study indicated that STF—which consists mainly of polyester fiber—was more stable in alkaline environment compared to commercial polyethylene terephthalate (PET) fibers. Relative to a plain reference mixture, 0.4% STF and 0.3% PET fibers reduced the plastic shrinkage crack area of mortar by 97.5% and 99.4%, respectively.
Recycled-rubber roads are not new; asphalt roads that incorporate rubber “crumbs” from shredded tires exist in the US, Germany, Spain, Brazil and China. But using the polymer fibers from tires has the unique benefit of potentially improving the resilience of concrete and extending its lifespan.
Our lab tests showed that fiber-reinforced concrete reduces crack formation by more than 90% compared to regular concrete. 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.—Obinna Onuaguluchi
UBC civil engineering professor Nemy Banthia, who supervised the work, says the environmental and industrial impact of the research is crucial. Up to three billion tires are produced around the world every year, generating close to three billion kilograms 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. We use almost six billion cubic meters of concrete every year. This fiber can be in every cubic metre of that concrete.—Nemy Banthia
Banthia is also scientific director of UBC-hosted Canada-India Research Center of Excellence (IC-IMPACTS), a center that develops research collaborations between Canada and India.
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.
The research has received support from IC-IMPACTS; Tire Stewardship B.C., the nonprofit that manages British Columbia’s tire recycling program; Atlantis Holdings Inc.; and recycler Western Rubber Products Ltd, which processed the fibers.
Onuaguluchi, O. & Banthia, N. (2017) “Durability performance of polymeric scrap tire fibers and its reinforced cement mortar” Mater Struct 50:158 doi: 10.1617/s11527-017-1025-7