ASTM C78/C78M-21 PDF Download

Standard Test Method ASTM C78/C78M-21 is used to determine the flexural strength of concrete specimens. The test method is applicable to specimens prepared and cured in accordance with other ASTM test methods such as C42/C42M, C31/C31M, or C192/C192M. The test results are reported as the modulus of rupture.

Various factors can affect the strength determined in this test method, including differences in specimen preparation, curing procedures, moisture condition at the time of testing, and whether the beam was molded or sawed to size. It is important to consider these variables when interpreting the results.

The modulus of rupture generally increases as the specimen size decreases. This information can be used to evaluate the effect of specimen size on the flexural strength of concrete.

The results obtained from this test method can be used to determine compliance with specifications, as well as for mixture proportioning, evaluating uniformity of mixing, and checking placement operations using sawed beams. The test method is primarily used in testing concrete for the construction of slabs and pavements.

It is worth noting that the modulus of rupture obtained by this test method may be lower, on average, compared to the modulus of rupture obtained by Test Method C293/C293M for identical test specimens.