Despite the widespread use of steel fibers in concrete reinforcement, their susceptibility to corrosion and handling hazards has accelerated the shift toward safer and more durable alternatives such as macro polypropylene (PP) fibers. In recent years, PP fibers have emerged as a promising substitute for steel fibers; however, their effectiveness in controlling cracking and enhancing residual strength of ground-supported slabs has not been fully established. This study investigates the flexural performance of fiber-reinforced concrete (FRC) incorporating steel and polypropylene fibers, tested in accordance with BS EN 14651 and ASTM C1609. A comprehensive experimental program was conducted on beam specimens reinforced with different fiber types, shapes, dosages, and aspect ratios to evaluate their influence on compressive and flexural behavior. The results demonstrate that fiber inclusion significantly enhances post-cracking strength and toughness. Hooked-end and high aspect ratio steel fibers produced the highest performance gains, while optimized PP fibers achieved comparable flexural performance at intermediate dosages. A direct correlation between the residual strengths obtained from the two testing standards was established, revealing a strong linear relationship. Finally, the measured residual strengths were implemented in ACI 360R and TR34 yield-line design methods to quantify slab thickness reductions. Both approaches confirmed the beneficial role of fibers in reducing slab thickness. Overall, the study highlights that fiber geometry and dosage are decisive parameters governing flexural response and demonstrates that properly optimized PP fibers can deliver performance comparable to steel fibers in structural applications.
Mohsen et al. (Fri,) studied this question.