Optimizing natural fiber content and types for enhanced strength and long-term durability in high-performance concrete

Fiber-reinforced concrete (FRC) is widely recognized for its enhanced ductility, energy efficiency, and sustainability. However, achieving these benefits without compromising mechanical and durability performance remains a challenge. Natural fibers have gained significant attention as a sustainable and cost-effective alternative to synthetic fibers due to their low carbon footprint. This study investigates the effects of incorporating three types of natural fibers—jute fibers (JFs), banana fibers (BFs), and coconut fibers (CFs)—into high-performance concrete (HPC), with volume fractions ranging from 0 % to 0.75 %. Their performance was systematically compared with that of polypropylene fibers (PPFs), a commonly used synthetic fiber in FRC. The results showed a reduction in workability with increasing fiber content, with JFs having the most significant impact. In terms of compressive strength, JFs provided slightly superior results compared to both PPFs and other natural fibers. For indirect tensile strength (ITS) and modulus of rupture (MOR), JFs and PPFs outperformed BFs and CFs. The optimum fiber volume fraction for enhancing ITS and MOR was identified as 0.60 %. At this dosage, BFs, JFs, and CFs improved ITS by 22–90 % and MOR by 46–96.5 % at both 28 and 90 days, relative to the reference HPC mix, indicating their substantial contribution to mechanical performance. However, fiber contents exceeding 0.75 % negatively affected the impermeability, capillary absorption, freeze–thaw resistance, and thermal performance of HPC. Despite these drawbacks, the fiber-reinforced mixes still performed better than the control mix. To mitigate the adverse effects of higher fiber contents, the incorporation of micro-silica and suitable chemical admixtures is recommended to preserve the integrity and durability of HPC while maximizing the benefits of natural fiber reinforcement.