Mechanical Properties of Fiber-Reinforced Concrete using Steel Fibers Derived from Discarded Tires

Abstract

Waste tire disposal poses a significant global challenge, with an estimated 1.5 billion tires discarded annually. Among various recycling approaches, extracting steel fibers from waste tires for use in concrete reinforcement has gained attention. This method not only reduces the volume of tire waste sent to landfills but also improves the mechanical performance of concrete. While concrete is widely valued for its versatility, it suffers from inherent limitations such as low tensile strength and brittle failure. The incorporation of steel fibers addresses these weaknesses by bridging cracks and enhancing post-cracking strength and toughness. Tires, which do not biodegrade naturally, are major contributors to environmental pollution and greenhouse gas emissions. This study explores the use of steel fibers recovered from discarded tires as a sustainable reinforcement material in concrete. The primary objective is to assess the impact of these fibers on concrete's workability, compressive strength, and tensile strength, using slump cone tests for workability evaluation. Concrete mixes were prepared with steel fiber dosages of 1%, 2%, 4%, and 6% by volume, alongside standard materials including cement, water, fine and coarse aggregates, and a superplasticizer. The results indicate that increasing the steel fiber content reduces the slump value—reaching as low as 20 mm at 4% and 6% content—due to the interlocking effect of fibers, which restricts the movement of the cement paste and aggregates while increasing internal friction. As fiber content increases, the concrete becomes stiffer and more cohesive, making placement and compaction more difficult. Nonetheless, the addition of steel fibers significantly enhances the tensile strength of concrete, with the most notable improvements observed at higher fiber dosages.