International Journal of Advance Engineering and Research Development (IJAERD) Volume 4, Issue 12, December-2017, e-ISSN: 2348 - 4470, print-ISSN: 2348-6406
Figure 5. Bond strength test setup Flexural strength is a measure of the tensile strength of concrete. It is a measure of resistance to failure in bending. The beams were tested for flexural strength after curing for 28 days in a Digitalized universal testing machine. The deflection in the beam is noted at regular intervals from the deflection dial gauge and the load at the point of failure is noted. The Concrete beam specimens are placed in the machine in such a manner that the load is applied to the uppermost surface as cast in the mould, along two lines spaced 20.0 or 13.3 cm apart. The axis of the specimen is carefully aligned with the axis of the loading device. The load is applied without shock and increasing continuously at a rate such that the extreme fibre stress increases at approximately 0.7 kg/sq.cm/min that is, at a rate of loading of 180 kg/min for the 10.0 cm specimens. The load is increased until the specimen fails, and the maximum load applied to the specimen during the test is recorded. The appearance of the fractured faces of concrete and any unusual features in the type of failure is noted. The flexural strength of the specimen is expressed as the modulus of rupture fb which if ‘a’ equals the distance between the line of fracture and the nearer support, measured on the centre line of the tensile side of the specimen, in cm, is calculated to the nearest 0.05 MPa as follows:
When ‘a’ is greater than 13.3 cm. or
when ‘a’ is less than 13.3 cm but greater than 11.0 cm. where b = measured width in cm of the specimen, d = measured depth in cm of the specimen at the point of failure, L = length in cm of the span on which the specimen is supported P = maximum load in kN applied to the specimen. The test setup is shown in Figure 6. The Flexural strength of each type of beam was obtained and the load-deflection characteristics of the beam up to the point of failure are reported in this paper.
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