PSI - Issue 70

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

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compared to the performance of the SR11 and SR12 beams, which had lower rubber content, the SR21 and SR22 specimens demonstrated that the increased proportion of sand-coated rubber shreds along with steel fibre reinforcement, results in a more significant gain in ultimate load-carrying capacity.

Fig.7 Response of Sand Coated rubber Aggregate and Steel Fibre Reinforcement on Ultimate Load The deflection behaviour of concrete beams is primarily influenced by factors such as the type and magnitude of loading, span length, the moment of inertia of the cross-section, and the elastic modulus of the concrete. In rubberized concrete beams, these parameters are further affected by the presence of rubber aggregates, which generally reduce stiffness. However, the incorporation of steel fibres counteracts this effect by enhancing the overall stiffness of the beam. This reinforcement improves performance throughout all stages of flexural loading - pre-cracking, cracking, and post-cracking by providing steel fibre that enhances load distribution, restricts crack development, and delays crack propagation.In this context, the test beams SR21 and SR22 demonstrated even greater improvements in deflection performance compared to earlier specimens. Specifically, SR21 and SR22 recorded increases in deflection at ultimate load by approximately 40% and 55%, respectively, in comparison to the control beam SC and the earlier test beams SR11 and SR12. These findings, detailed in Table 4 and illustrated in Fig .8, highlight the significant impact of using higher rubber content in combination with steel fibres. The enhanced deflection capacity observed in SR21 and SR22. The sand-coated rubber coarse aggregates improved the bond with the cement matrix, while the steel fibres provided resistance against crack widening and supported sustained load-carrying capacity after cracking. This synergistic effect resulted in superior deformability and resilience under flexural loading.

Fig.8 Response of Sand Coated Rubber Aggregate and Steel Fibre reinforcement on Deflection at Ultimate Load

Table 5 Test Results of Rubberized Concrete Beam (S31&S32)

SI.No

Identification of beams

First crack (k N)

Deflection at FCL (mm)

Yield Load (k N)

Def @YL

Ultimate Load (k N)

Deflection at Ultimate

1.

SR31

25.75

3.28

42.50

7.95

69.75

20.80

2.

SR32

27.50

3.35

45.00

8.10

72.50

24.90

The ultimate load for the sand-coated rubberized concrete beams with steel fibre reinforcement, SR31 and SR32, are presented in Table 5. These beams showed substantial improvements in structural performance, with SR31 and SR32 exhibiting increases of 16.25% and 20.83%, respectively, when compared to the control beam SC. The results, as shown in Fig. 9, clearly indicate that the combined use of sand-coated rubber coarse aggregates and steel fibres significantly influences the ultimate load-bearing capacity of the beams. When compared to the SR21 and SR22 beams, which showed load increases of 10.83% and 14.16% respectively, the SR31 and SR32 beams demonstrated even