PSI - Issue 70

Vudata Harsha sai et al. / Procedia Structural Integrity 70 (2025) 509–516

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Fig.10 Load vs Deflection for M 40 FA Mix

Fig.11 Load vs Deflection for M 40 FA - SF Mix

Fig.12 Load vs Deflection for M 40 FA - PPF Mix

Fig.13 Load vs Deflection for M 40 FA - CYF Mix

4. Conclusion This experimental study demonstrates that 20% Class F fly ash replacement coupled with 1% hybrid fiber reinforcement (steel, polypropylene, coir yarn) offers the best balance of strength, ductility, and sustainability for M40 concrete: • Replacing cement with 20% Class F fly ash provided the best balance between strength and workability, improving compressive strength while enhancing sustainability by reducing CO₂ emissions. Although 30% replacement slightly reduced strength, it still offered environmental benefits. Incorporating steel, polypropylene, and coir yarn fibers significantly improved compressive, tensile, and flexural strength due to their crack-bridging capacity and energy absorption capabilities. 20% fly ash optimizes pozzolanic reactions (Mohanraj & Vidhya, 2023); steel fibers further increase compressive strength by ~10% and split tensile strength by ~24% (Loganathan et al., 2022; Mohanraj et al., 2023). • Steel fibers contributed to substantial strength gains (up to 30% in flexural strength), polypropylene fibers reduced shrinkage cracking and improved ductility, and coir yarn fibers offered natural toughness and impact resistance. Hybrid combinations outperformed single-fiber mixes in terms of mechanical behavior, post-cracking resistance, and deflection control, especially in structural beam applications. Steel fibers achieve the highest flexural gain (+34%) (Gopalakrishnan et al., 2024), while polypropylene and coir yarn fibers improve energy absorption and crack control (Ali et al., 2012; Enhancing concrete flexural behaviour with Euphorbia tortilis, 2024). • The combined use of fly ash and natural fibers like coir supports circular economy goals and presents a viable path toward sustainable construction. Further research is recommended to evaluate long-term durability aspects such as chloride penetration, freeze-thaw resistance, and optimized fiber proportions to improve structural performance in diverse conditions. Fly ash reduces cement demand and CO₂ footprint (Mehta & Monteiro, 2014), and coir yarn introduces a biodegradable reinforcement, supporting circular-economy principles (Mohanraj et al., 2023). • Load – deflection behaviour confirms superior post-cracking response in hybrid mixes, aligning with cyclic-load studies on fiber-reinforced beams (Loganathan et al., 2022; Ravikumar et al., 2023).Overall, the synergistic combination of optimized fly ash and hybrid fibers produces a sustainable, high-performance concrete suitable for structural applications demanding enhanced durability, crack resistance, and ductility. Future work should explore