Influence of Basalt and Bamboo Fibres in Various Locations of Reinforced Concrete Beams

The addition of fibres to reinforced concrete (RC) beams improves ductility, reduces crack width, and controls crack propagation. Although steel fibres are conventionally used, their environmental cost is high. This study investigates a sustainable alternative using natural (bamboo) and mineral (basalt) fibres in hybrid combinations. Four RC beams (0.15 × 0.20 × 1.50 m) were tested under four-point bending until failure. Two beams served as controls (one fully reinforced, one without shear reinforcement) and two contained hybrid fibres (1% bamboo + 0.75% basalt); one hybrid beam was reinforced along the entire span (BHFFR), the other only in the shear region (BHFPR). Results are presented in terms of load–deflection curves, crack patterns, and failure modes. BHFFR showed a 9.37% increase in yield load (from 99.29 kN to 109.56 kN) and a 0.5% increase in ultimate load over the fully reinforced control (from 116.88 kN to 117.44 kN). For BHFPR (reinforced only in shear), the yield load increased by 29.46% (from 55.66 kN to 78.90 kN), and the ultimate load improved by 6.78% (from 86.98 kN to 93.30 kN). Hybrid fibre reinforcement successfully reduced crack propagation and controlled crack widths relative to non-fibrous beams, demonstrating their potential as environmentally friendly substitutes for steel fibres in RC beams.