Measuring the modulus of rupture of refractories at elevated temperatures has become a widely accepted means to evaluate materials at service temperatures. Many consumer companies have specifications based on this type of test.

This test method is limited to furnaces operating under oxidizing conditions. However, with modifications for atmosphere control in other test furnaces, the major criteria of this test procedure may be employed without change.

This test method is designed for progressive application of a force or stress on a specimen supported as a simple beam with center-point loading. Test apparatus designed for the progressive application of a strain may yield different results, especially since refractory materials will reach a semiplastic state at elevated temperatures where Hooke'law does not apply, that is, stress is then not proportional to strain.

This test method applies to fired dense refractory brick and shapes, chemically bonded brick and shapes, shapes formed from castables, plastics, or ramming materials, and any other refractory that can be formed to the required specimen dimension.