Riprap is commonly used to prevent erosion of underlying materials due to the effects of rain runoff, wind, flowing water, or wave action. The particle size distribution (mass of particles) is an important physical characteristic of riprap, as discussed in D 6825. These test methods provide a gradation of the material graphically represented as percent finer than the particle mass. If a gradation can be established or accepted on the basis of only maximum and minimum particle sizes, then it may not be necessary to establish the complete gradation in accordance with these test methods.

These test methods can be used during evaluation of a potential source, as a means of product acceptance, or for assessment of existing installations. Method D is not recommended as a means of product acceptance.

Other characteristics of interest, such as particle shape, particle angularity, or visually evident rock durability characteristics may be determined during the performance of these test methods.

Interpretation of test results must consider the representativeness of the sample.

Note 2-The agency performing these test methods can be evaluated in accordance with Practice D 3740. Not withstanding statements on precision and bias contained in these test methods: The precision of these test methods is dependent on the competence of the personnel performing it and the 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. Users of these test methods are cautioned that compliance with Practice D 3740 does not in itself ensure reliable testing. Reliable testing depends on many factors; Practice D 3740 provides a means of evaluating some of those factors.