Rock riprap is composed of pieces of natural rock that are placed on construction projects to minimize the effects of erosion. The ability of riprap to withstand deterioration from weathering affects both the effectiveness of the project and its cost. The sodium sulfate or magnesium sulfate soundness test is one method by which to estimate qualitatively the durability of rock under weathering conditions.

Note 1-The quality of results produced by this standard is dependent on the competence of the personnel performing it and suitability of the equipment and facilities used. Agencies that meet the criteria of Practice D 3740 are generally considered capable of competent and objective testing. Reliable results depend on many factors and Practice D 3740 provides a means of evaluating some of them.

The results of this test method are not to be used as the sole basis for determination of rock durability, but rather should always be used in conjunction with the results of other tests.

This test method has been used to evaluate many different types of rocks. There have been occasions when test results have provided data that have not agreed with the durability of rock under actual field conditions; samples yielding a low soundness loss have disintegrated in actual usage, and the reverse has been true.