PSI - Issue 70

K. Navin Balaji et al. / Procedia Structural Integrity 70 (2025) 295–302

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stiffness and rigidity throughout the concrete matrix. The denser concrete microstructure and improved particle packing from LSP result in the elasticity increase up to 15% RHA content. The lower modulus of CSA may have caused a minor reduction in stiffness increase because of its dissimilar modulus in relation to NCA.

Fig. 5. Test findings on modulus of elasticity

3.2.6. Ultrasonic Pulse Velocity (UPV) test All concrete samples achieved UPV readings between 4.18 km/s and 4.48 km/s indicating "Good" performance following IS 13311 criteria. RHA-15 exhibited the peak ultra-high frequency value of 4.48 km/s that corresponds to its maximum compressive strength and elastic modulus according to the study findings. The dense microstructure with uniform distribution and few internal voids originated from using RHA in combination with LSP and CSA. The observed mechanical behaviour shows support from a modest UPV decrease which occurs beyond 15% RHA levels. Fig.6. illustrates the outcomes of the UPV test.

Fig.6. UPV test results

4. Conclusion The research explored the fresh characteristics along with mechanical properties of SCC containing RHA cement replacements with fixed LSP and CSA dosages. The workability of all SCC mixes satisfied EFNARC guidelines for SCC standards through slump flow, T500 time, L-box ratio, V-funnel and J-ring tests which demonstrated good flowability and passing ability. The substitute of cement with RHA improved compressive strength until reaching its peak value of 40.12 MPa at 28 days with a 15% RHA content. The strength values decreased after reaching their peak but all mixtures retained suitable strength levels. The optimal blend exhibited a 20.66% increase in performance relative to the conventional concrete (CC) mix. The split tensile and flexural strength measurements revealed better performance up to 15% RHA because the pozzolanic reaction of RHA improved bond strength and matrix development. The dry density of SCC decreased steadily as RHA content increased from 1995 kg/m³ for CC to 1800 kg/m³ for RHA-25 which demonstrates that the mix weight decreased because of RHA and CSA together. The continuous addition of LSP at 15% cement replacement helped improve packing density and accelerated early strength