Experimental study on the static properties of bamboo fiber reinforced ultra-high performance concrete (UHPC)

Bamboo fiber, as a natural and sustainable material, offers low cost, high strength, and environmental benefits, showing significant potential in composite material reinforcement. This study investigates the effects of bamboo fiber on the static properties of ultra-high performance concrete (UHPC) through experimental research. Different fiber lengths (6 mm, 12 mm, 18 mm) and volume contents (0.5 %, 1.0 %, 1.5 %, 2.0 %) were examined for their impact on the workability, mechanical properties, and pore/void structure of UHPC. The results demonstrate that while bamboo fiber incorporation reduces workability, it significantly enhances compressive and flexural strengths. Specifically, a 21.9 % increase in compressive strength was achieved with 18 mm fibers at 1.0 % content, and a 40.5 % increase in flexural strength was observed with 18 mm fibers at 1.5 % content. Mercury intrusion porosimetry (MIP) and computed tomography (CT) revealed that longer fibers contribute to the formation of larger pores, affecting the void structure. Moreover, bamboo fibers degrade over time in alkaline environments, with a 5 % reduction in tensile strength after 28 days, but the crystallinity of the cellulose has increased. Based on the experimental results, 12 mm bamboo fibers at 1.0-1.5 % content provide the best balance of strength enhancement and workability, making them a promising reinforcement material for UHPC.