PSI - Issue 70

R. Karthikeyan et al. / Procedia Structural Integrity 70 (2025) 89–96

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greater enhancements in strength. This suggests that the adjustments made in the SR31 and SR32 specimens potentially involving higher rubber content, fibre dosage, further amplified the beneficial effects of the sand coating and fibre reinforcement. The improved bonding from the sand-coated rubber aggregates, along with the enhanced crack bridging ability of steel fibres, contributed to better stress distribution and delayed failure, resulting in higher ultimate load.

Fig. 9 Response of Sand Coated Rubber Aggregate and Steel Fibre Reinforcement on Ultimate Load The test results for beam specimens SR31 and SR32 reveal a significant increase in deflection at ultimate load, with SR31 and SR32 showing increases of 73.33% and 107.5%, respectively, compared to the control beam SC. These results, presented in Table 5 and illustrated in Fig .9, clearly demonstrate that the combined effect of sand-coated rubber coarse aggregates and steel fibres has a considerable impact on the deflection behaviour of the beams at ultimate load. When compared to the earlier beams SR21 and SR22, which exhibited increases in deflection at ultimate load of 40% and 55%, the SR31 and SR32 beams show a much higher level of deflection. This suggests that the modifications in SR31 and SR32 — such as higher rubber content, more fibre reinforcement, or improved aggregate treatment — resulted in a more significant enhancement in deformability and ductility.

Fig.10 Response of Sand Coated Rubber Aggregate and Steel Fibre Reinforcement on Deflection on Ultimate Load

4. Conclusions 1. The study demonstrates that concrete beams incorporating 7.5% rubber shreds and 1.0% steel fibre by volume exhibit a significant enhancement in structural performance, with up to a 20.83% increase in ultimate load capacity and a remarkable 107.5% improvement in deformation capacity compared to conventional concrete. 2. This enhanced performance is largely attributed to the application of a resin-based sand coating on the rubber shreds, which effectively strengthens the interfacial bond between the rubber aggregates and the cementitious matrix, thereby improving stress transfer and overall material cohesion. 3. The combined use of sand-coated rubber and steel fibres contributes to greater load resistance, improved crack control, and enhanced post-peak behaviour. These results highlight that the strategic optimization of rubber content, surface treatment, and steel fibre dosage can lead to the development of durable, ductile, and sustainable concrete suitable for modern structural applications.