Mechanical Behavior and Durability Performance of Concrete Reinforced with Hybrid Date Palm and Polypropylene Polymer Fibers

Concrete faces challenges related to brittleness and crack propagation, which compromise its tensile strength and durability. Fiber reinforcement has emerged as a promising solution, yet research on hybrid systems combining natural fibers, such as date palm fiber (DPF), with synthetic polymer fibers, like polypropylene fiber (PPF), remains limited. This study investigates the mechanical and durability performance of concrete reinforced with hybrid DPF and PPF, aiming to address the gap in understanding the synergistic effects of combining natural and synthetic fibers in cementitious materials, and improving the tensile strength and crack resistance of the concrete. Both the DPF and PPF were added at varying dosages (0%, 0.25%, 0.5%, 0.75%, and 1% by weight of cement). Both DPF and PPF reduced the workability, fresh density and compressive strength of concrete, with DPF exhibiting a more significant reduction due to its higher hydrophilicity and poor compatibility with the cement matrix. A maximum reduction of 44.78% was observed in the mix containing 1% DPF and 0.5% PPF. The fibers improved tensile strength and ductility, with mixes containing up to 1% combinations of DPF and PPF showing up to a 14.6% increase in splitting tensile strength and 9.5% improvement in flexural strength compared to the control mix. However, durability was compromised-water absorption increased by up to 58% in hybrid mixes containing 1.5% total fiber content, while pore volume rose by as much as 17.5% compared to plain concrete. These increases were more pronounced with higher DPF content due to its hydrophilic nature and poor cement compatibility. This study highlights the potential of hybrid fibers to improve concrete performance while promoting eco-friendly and cost-effective solutions.