Synergistic Effects of Manufactured and Recycled Steel Fibers in Paving Concrete Mixtures

The cracking issues in concrete pavements caused by shrinkage, vehicular loading, and other factors can be mitigated by using steel fibers. However, the high cost and environmental impact of manufactured steel fibers (MSFs) necessitate alternative solutions. This study explores recycled steel fibers (RSFs) from waste tires as a sustainable alternative. The combined use of RSFs and MSFs, referred to as hybrid steel fibers (HSFs) in this study, is also explored. RSFs offer economic and environmental benefits, significantly improving the mechanical properties and durability of concrete. Testing reveals that flexural strength improves by around 36, 20, and 30%, and tensile strength by 53, 23, and 39% with MSFs, RSFs, and HSFs, respectively. Additionally, MSFs reduced the drying shrinkage by around 14%, RSFs by 10%, and HSFs by 18%. Incorporating MSF, RSF, and HSF enhances fracture resistance, improving ductility and crack-bridging effects compared to normal paving concrete. Key fracture properties indicate that HSF provides the best crack control and energy absorption capacity, followed by MSF and RSF.