what is the flexural strength of concrete?
Flexural strength is one measure of the tensile strength of concrete. It is a measure of an unreinforced concrete beam or slab to resist failure in bending. It is measured by loading 6 x 6 inch (150 x 150-mm) concrete beams with a span length at least three times the depth.
Flexural test evaluates the tensile strength of concrete indirectly. It tests the ability of unreinforced concrete beam or slab to withstand failure in bending. The results of flexural test on concrete expressed as a modulus of rupture which denotes as (MR) in MPa or psi. The flexural test on concrete can be conducted using either three point load test (ASTM C78) or center point load test (ASTM C293). The configuration of each test is shown in Figure-2 and Figure-3, respectively. Test method described in this article is according to ASTM C78.
Why is most important flexural strength of concrete?
The most common significance of a flexure test is to measure flexural strength and flexural modulus. Flexural strength is defined as the maximum stress at the outermost fiber on either the compression or tension side of the specimen. Flexural modulus is calculated from the slope of the stress vs. strain deflection curve.
High flexural strength is essential for stress-bearing restorations, when high pressure/stress is exerted on the material or restoration. As a result, flexural strength also determines the indications for which a material can be used: The more strength a material offers, the more units a restoration can include.
Formula is flexural strength of concrete?
Stresses caused by the bending moment are known as flexural or bending stresses. Consider a beam to be loaded as shown. Consider a fiber at a distance y from the neutral axis, because of the beams curvature, as the effect of bending moment, the fiber is stretched by an amount of cd.
How to perform flexural strength of concrete?
Design of the thickness of concrete road are based on the flexural strength or MR. Factors include traffic loading and subgrade stiffness. Pavement designers often require validation that the proposed mixture will achieve the MR used in design.
Flexural strength is conservatively neglected in calculating the nominal flexural strength for design of structural members. The flexural strength, estimated from the empirical relationship, is used estimate the tensile stress that causes cracking of non-reinforced concrete and to evaluate deflections at service loads.
Size of Concrete Specimen for Flexural Test
Size is consideration too much important
According to ASTM the size of the specimen is 150mm width, 150mm depth and the length should not be at least three times the depth of the specimen. Indian standard determined the size of the concrete specimen as 150mm width, 150mm depth, and span of 700mm. It also states that a size of 100mm width, 100mm depth, and span of 500mm can be used if the maximum aggregate size used is not greater than 19mm. British standard specifies square specimen cross section with 100mm or 150mm dimension and the span ranges from four to five times specimen depth. However, it preferred 150mm width, 150mm depth, and span of 750mm for the specimen.