PSI - Issue 70

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

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Recent work on cactus-based bio-admixtures also reports similar compressive gains under static loads (Pattusamy et al., 2023). 3.2 Split Tensile Strength Split tensile strength was determined using 150 mm × 300 mm cylindrical specimen, per IS 5816:1999. Testing was made with a Universal Testing Machine under a controlled load, along the cylinder length, until failure. Maximum load was the one that was used in finding the tensile strength, which was the ability of concrete to resist the tensile stress. A comparative study of the split tensile strength of FRC along the longitudinal direction (with cylindrical specimens under diametral compression) in the compliance to IS 5816:1999 has been conducted. The control mix M 40 – Control recorded a 28 split tensile strength of 3.8 MPa. This added 10% and 20 % Class F fly ash: increased strength to 4. 1 MPa (M40-FA10) and 4. 3 MPa (M40-FA20) respectively and increased the particle packing as well as enhanced the interfacial transition zone (ITZ) due to pozzolanic effects However at 30% fly ash (M40-FA30), tensile strength was lowered to 3.6 MPa, which means lower efficiency of matrix bonding. The highest strength, 5.2 MPa was given by the steel fibers (M40-FA20-SF), the crack-bridging and stress redistribution were the factors corresponding to the highest strength. Series of polypropylene fibers (M40-FA20-PPF) were subjected to 4.7 MPa; thus, enhancing its performance with regard to premature crack development. Coir yarn’s fibers (M40 -FA20-CYF) achieved 4.5 MPa in order to improve ductility and toughness. The results support the increase in crack resistance, durability and tensile strength of concrete due to the replacement of 20% fly ash and introduction of fiber.

Fig.4 Split strength Test setup Fig.5 Split strength Results Split tensile tests (Fig. 5) show an increase from 3.8 MPa (control) to 4.3 MPa with 20% fly ash, due to improved interfacial transition zone (Neville, 2011). Steel-fiber reinforcement raises tensile strength to 5.2 MPa, corroborating Sivaraja et al. (2010) and Mohanraj et al. (2023) on enhanced crack-bridging. Polypropylene fibers yield 4.7 MPa and coir yarn 4.5 MPa, reflecting their capacity to delay crack propagation and improve toughness (Mohanraj, Senthilkumar, & Padmapoorani, 2022). 3.3 Flexural Strength Flexural strength was done by three point bending test of Prisms 500 × 100 × 100 mm – IS 516:2020. A Universal Testing Machine was used to bring a central load to failure rate. The load of rupture obtained at the maximum load recorded was used to compute the modulus of rupture which represents the bending strength. Flexural strength which is the ability of material to resist cracking and to bear load was determined for fiber reinforced concrete (FRC) using 500 × 100 × 100 mm prism specimens under three-point bending – as per IS 516: 2020. The best mixture (M40 – Control) had flexural strength of 5.8MPa at 28 days. Fly ash replacements of 10% and 20% provided strength of 6.2 MPa and 6.5 MPa due to fine microstructure and better interfacial transition zone by virtue of pozzolanic activities. Although an M40-FA30 (30% replacement) compromised the matrix and strength to 5.4 MPa. Addition of 1% steel fibers (M40-FA20-SF) increased flexural strength to 7.8 MPa because of the ability of crack bridging and stress transfer. Upon the arrest of microcracks in polypropylene fibers enhanced strength (M40-FA20-PPF) improved to 7.0 MPa and coir yarn fibers (M40-FA20-PYF) achieved strength of 6.8 MPa, resulting to gain of energy absorption and ductility. Overall, the best performance under flexural conditions was achieved at 20% of fly ash and steel fibers, signifying great synergism for long lasting high performance concrete applications.