PSI - Issue 70

J. Arun Prasad et al. / Procedia Structural Integrity 70 (2025) 690–697

695

The flexural strength of M20 grade concrete was enhanced by partial replacement of cement with 10% Cenospheres. Strength improvements of approximately 8 – 13% were observed at 7-, 14-, and 28-days curing ages compared to conventional concrete. This suggests that Cenospheres contribute positively to the flexural performance of concrete, improving its suitability for structural applications where bending resistance is critical. 6. Flexural Strength Test for Beam A concrete mix with a 1:1.5:3 ratio (cement: sand: coarse aggregate) and a water-cement ratio of 0.5 was prepared by thoroughly dry mixing the materials before gradually adding water to ensure uniformity. The fresh mix was tested immediately for workability. Specimens were cast in standard moulds, including cubes and beams (1000 mm × 230 mm × 230 mm) for flexural strength evaluation. After 24 hours of curing under laboratory conditions, samples were demoulded and cured in water for 28 days at ambient temperature. Following curing, beam specimens were air-dried and tested for flexural strength using a two-point loading system, where load was gradually applied until failure occurred. The maximum load at failure was recorded to assess the flexural capacity.

Fig. 4. Beam Subjected to Point Load in Loading Frame a) Conventional Concrete beam b) 10% Replacement of Cenosphere Concrete beam

Table 5 Beam Result (10% Replacement of Cenosphere)

First crack Load (kN)

Deflection at first crack (mm)

Ultimate load (kN)

Ultimate deflection (mm)

Beam No

CC1

20.3

0.13

36

1.6

CC2

21.2

0.15

38

1.7

CCC 10% CCC 10% CCC 10%

12.26

1.06

17.17

1.26

14.72

1.46

26.20

1.86

17.16

1.88

31.98

1.98

Flexural strength tests on M20 grade concrete beams demonstrated that partial replacement of cement with 10% Cenospheres resulted in a reduction in both first crack and ultimate loads compared to conventional concrete. However, beams with Cenospheres exhibited significantly higher deflections at cracking and failure, indicating enhanced ductility and energy absorption capacity. This suggests that while Cenospheres may slightly compromise peak load-bearing strength, they improve the flexibility and toughness of concrete beams, making them suitable for applications requiring improved deformation performance.