PSI - Issue 70

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

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Fig.6 Flexural strength Test setup Fig.7 Flexural strength Results Under three-point bending (Fig. 7), the 20% fly ash mix reaches 6.5 MPa — an 12% improvement — mirroring results reported for fly ash – fiber systems (Yin et al., 2015). Steel fibers elevate flexural strength to 7.8 MPa, a 34% increase, in agreement with Gopalakrishnan et al. (2024) on PVA-fiber composites. Polypropylene (7.0 MPa) and coir yarn (6.8 MPa) similarly enhance post-peak toughness (Ali et al., 2012; Enhancing concrete flexural behaviour with Euphorbia tortilis, 2024). 3.4 Load-Deflection Characteristics A two-point bending test was conducted on 700 × 150 × 150 mm concrete beams with a 600 mm effective span. Two symmetrical loads were applied using a UTM. LVDTs measured deflections at mid-span and loading points. The test evaluated flexural response, ductility, cracking behaviour, and energy absorption. Two-point bending tests on 700×150×150 mm beams showed the M40-Control exhibited linear response until brittle failure. Substituting 20% fly ash (M40-FA20) refined the matrix, delayed cracking, and improved flexural behavior; 30% fly ash reduced stiffness. Adding steel fibers (M40-FA20-SF) maximized capacity and ductility, polypropylene enhanced crack resistance, and coir yarn provided moderate strength with improved deformation. Load – deflection curves (Figs. 9 – 13) demonstrate that the 20% fly ash + steel fiber beams exhibit significantly enhanced ductility and energy absorption, delaying crack initiation and softening more gradually. This behavior aligns with Silva et al. (2023) on sustainable fiber systems. Polypropylene-reinforced beams show improved post-peak resistance, while coir yarn beams display higher deformation capacity — valuable for seismic resilience (Mohanraj et al., 2023; Pattusamy et al., 2023).

Fig 8. Loading Frame Setup

Fig.9 Load vs Deflection for M 40 Control Mix