Recycling Scrap Tire-Derived Fibers in Concrete

This paper describes results of several studies undertaken by the authors in the bid to valorize both Scrap Tire Polymeric Fiber (SPF) and Scrap Tire Steel Fiber (SSF) as value-added reinforcements in cement-based composites. Current scrap tire by-product management practices, fiber characteristics, and their influence on the plastic shrinkage cracking and the mechanical post-crack response of cement-based materials were examined. Details of an instrumented demonstration project, where the SPF was used as a microfiber reinforcement in a rigid concrete pavement for use as a vehicle parking facility in a First Nations community in Canada are also given. SPF used was 18–20 µm wide and 3–5 mm long with a scarified surface and attached crumb rubber particles. The SSF, on the other hand, had two broad size classifications; 10–13 mm and 13–16 mm long fibers and 0.2–0.3 mm diameter. Relative to plain mortar, 0.4% mass fraction of the SPF caused about 97.5% reduction in the shrinkage crack area. This performance was comparable to that imparted by 0.3% of virgin commercial polyethylene terephthalate (PET) fiber. Although the short length of the SPF precludes it from having any flexural post-crack control benefit, its hybridization with steel macro-fiber led to a synergistic enhancement of the post-cracking toughness and residual strength of mortar. Similarly, an addition of the SSF to Ordinary Portland Cement (OPC) and Alkali-Activated Matrices (AAM) led to significant toughness improvements. Finally, strain data from the demonstration project indicated that the pavement with the SPF reinforcement had a significantly reduced propensity to cracking compared to the one without. While these results suggest an enormous potential for scrap tire derived fibers for use in concrete as reinforcement, the authors believe that significant further improvements in the performance characteristics are possible.