ASTM D4718/D4718M-15 PDF Download

ASTM D4718/D4718M-15 is a standard practice that provides a procedure for correcting the unit weight and water content of soils containing oversize particles. Compaction tests on soils typically have limitations on the maximum size of particles that can be used. If a soil contains cobbles, gravel, or other oversize particles, test options may be selected where these particles are discarded, and the test is performed on the finer fraction. However, the unit weight and water content determined from these tests only reflect the characteristics of the tested material, not the total soil material.

This standard practice is commonly used in engineering for the design, specification, and construction control of soils used in earth construction. When large particles are present in the soil, and only the finer fraction is used for laboratory tests, there is a need to correct the laboratory test results to reflect the characteristics of the total soil. This practice provides a mathematical equation for correcting the unit weight and water content of the finer fraction of a soil, based on the unit weight and water content of the total soil.

The practice is also applicable for correcting the unit weight and water content of field compacted samples of the total soil, so that values can be compared with those for a laboratory compacted finer fraction. However, it should be noted that the calculated values of percent compaction based on this correction practice will vary depending on whether the unit weight value used for reference includes the oversize fraction or is based on the finer fraction.

This standard practice presents various considerations and limitations for its application. The maximum permissible percentage of oversize particles depends on whether interference between the oversize particles affects the unit weight of the finer fraction. The practice is considered valid for materials with up to 40% oversize particles retained on the 4.75-mm sieve, and up to 30% oversize particles retained on the 19-mm sieve. However, the person or agency using this practice should determine if a lower percentage needs to be used for specific gradations. Additionally, the correction may not be significant for soils with small percentages of oversize particles, but this minimum percentage can be specified by the person or agency.