Summary of Test
ASTM C78 determines the flexural strength of concrete by the use of a simple beam with third-point loading. Results are reported as the modulus of rupture (MOR), which is the flexural strength of the concrete sample just before it yields.
A testing machine, capable of applying and monitoring loads at a uniform rate without shock or interruption, and a three-point flex apparatus as prescribed in the standard should be used to calculate the MOR. Before conducting ASTM C78, it is important to read the entire specification in the relevant ASTM publication.
Recommended Equipment
Testing Procedure
- Enter/record the specimen information required by the standard in section 9 such as but not limited to: ID number, sample dimensions span length and curing history.
- Place the specimen in the flex apparatus as described in the standard.
- Apply load continuously, at a constant rate as found in the testing standard, without shock until the sample ruptures.
- Make sure the load indicator is set to zero prior to starting the test.
- Apply load continuously, at a constant rate, without shock until failure.
- Record the maximum load carried by the specimen during the test.
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