Reducing steel fiber segregation and enhancing UHPC performance with hybrid bamboo fibers: An eco-friendly approach

Ultra-high-performance concrete (UHPC) has gained widespread attention in civil engineering due to its superior mechanical properties and durability. However, the high cost, density, and susceptibility to segregation of steel fibers during construction limit its broader application. Bamboo fiber, a natural plant fiber characterized by its wide availability, low cost, and environmental friendliness, offers high tensile strength and hygroscopic properties, making it a promising alternative or complementary reinforcement to steel fibers. This study systematically investigates the effects of combining bamboo fibers with steel fibers on the microstructure and macro-scale performance of UHPC. Results reveal that incorporating bamboo fibers significantly enhances internal humidity stability within UHPC, achieving a maximum reduction of autogenous shrinkage by 53.7 %. Additionally, bamboo fibers effectively mitigate the segregation of steel fibers, promoting a more uniform distribution. By adjusting fiber orientation and distribution patterns, bamboo fibers improve the overall material consistency, reducing flexural performance variability by over 90 %. Although the high hygroscopicity of bamboo fibers decreases the workability of fresh concrete, their positive effects on early-age crack resistance and long-term durability have been validated. This study provides scientific evidence supporting the practical application of bamboo fibers in UHPC and introduces a novel approach to developing low-carbon, sustainable construction materials.