Experimental investigation on mechanical and durability properties of twisted basalt fiber reinforced concrete

The corrosion of steel reinforcement is a major challenge for concrete structures in marine environments, reducing their durability and structural integrity. While steel fibers are commonly used in Fiber Reinforced Concrete (FRC), their susceptibility to corrosion and pitting has led researchers to explore non-metallic alternatives. Basalt fiber, a non-metallic material, offers numerous advantages, including high tensile strength, non-toxicity, and excellent resistance to acidic and corrosive environments. This study investigates the mechanical and durability properties of Basalt Fiber Reinforced Concrete (BFRC) with twisted basalt fibers at different volume fractions. Four mixtures containing 0%, 0.5%, 1%, and 1.8% fiber content were prepared and compared to Normal Concrete (NC). Mechanical properties, including compressive strength, splitting tensile strength, and modulus of rupture (MOR), were assessed. The results indicated that compressive strength marginally increased from 48.4 MPa for NC to 51.3 MPa for BFRC-1.8, representing a 6% improvement attributed to the crack-bridging action of the fibers. More notable were the enhancements in splitting tensile strength, which increased from 2.8 MPa in NC to 4.1 MPa in BFRC-1.8, reflecting a 46% gain. The incorporation of twisted basalt fibers also shifted the failure mode from brittle to ductile, enabling the concrete to absorb and dissipate more energy before failure. Flexural performance, measured via MOR, improved by 15%, 40%, and 81% for fiber additions of 0.5%, 1%, and 1.8%, respectively, with corresponding increases in toughness values reaching up to 364%. These results demonstrate the superior energy absorption and resilience of BFRC under loading. Durability properties, including water penetration depth, water absorption, electrical resistivity, and performance under accelerated corrosion testing, were also evaluated. Durability assessments showed marked improvements with increased fiber content. Water penetration depth decreased substantially (by 18–53%), while water absorption dropped from 2.3% in NC to 1.28% for BFRC-1.8, confirming the ability of fibers to reduce porosity and fill microcracks, thereby protecting internal steel from ion ingress. Electrical resistivity tests revealed that greater fiber content produced higher electrical resistance, further impeding the initiation and progression of corrosion. Results from accelerated corrosion testing demonstrated that twisted basalt fibers are highly effective in mitigating steel rebar corrosion. Corrosion rates were substantially reduced from 0.55 mm/year in NC to 0.25, 0.16, and 0.09 mm/year for BFRC-0.5, BFRC-1, and BFRC-1.8, respectively. Similarly, rebar weight loss decreased from 49.9% in NC to 22.7%, 14.1%, and 8.6% in the respective BFRC mixtures. The time to the first visible crack caused by corrosion was delayed, increasing from 55 days in NC to 74 days in BFRC-1.8. These findings indicate that twisted basalt fibers effectively impede the passage of aggressive ions, markedly improving the durability of reinforced concrete in severe environments. In summary, incorporating twisted basalt fibers into concrete blends offers measurable benefits in both mechanical and durability properties, with a pronounced effect in suppressing steel reinforcement corrosion, making BFRC a highly promising, sustainable material for marine infrastructure