MECHANICAL PERFORMANCE OF HYBRID FIBER-REINFORCED CONCRETE: THE SYNERGISTIC EFFECT OF RAMIE AND MICRO SYNTHETIC FIBERS

Abstract

Conventional concrete has limitations in tensile strength and crack control. Fiber-reinforced concrete improves these properties, but single fiber types can hinder performance. While steel fibers are common, synthetic and natural fibers are gaining traction due to their cost-effectiveness, performance, and eco-friendliness. This research explores hybrid fiber concrete using micro synthetic (polyamide, 12 mm, 0.06% fiber volume fractions) and natural ramie (19 mm, 0.25%, 0.50%, 0.75% by cement weight) fibers to enhance mechanical performance. Five mix designs (V1-V5) were evaluated for compressive strength, splitting tensile strength, and modulus of elasticity at 28 days. Results showed that plain concrete (V1) had the highest compressive strength of 32.44 MPa but suffered brittle failure. V2 (micro synthetic fibers only) showed the lowest strength, indicating limited effectiveness. The addition of hybrid fibers (V3-V5) significantly increased the splitting tensile strength of concrete by 0.99-15.84% and modulus of elasticity by 101.73-198.05% higher than plain concrete. Hybrid fibers also transformed the failure mode from brittle to ductile. The V4 mixture represents the most effective combination of strength, stiffness, and crack resistance. This research highlights the synergistic potential of hybrid fiber reinforcement for improving concrete's tensile capacity, stiffness, and post-cracking behavior, offering valuable insights for durable concrete applications.