AASHTO T 180-21 PDF Download

The AASHTO T 180-21 standard method of test is used to determine the moisture-density relationship of soils. It involves compacting soil samples in a mold of a specific size using a 4.54-kg (10-lb) rammer, which is dropped from a height of 457 mm (18 in.). The standard provides four alternate procedures, designated A, B, C, and D, depending on the size of the mold and the sieve size of the soil material being tested.

The standard specifies that the method to be used should be indicated in the material specifications. If no method is specified, Method A is the default. The test method applies to soil mixtures with 40 percent or less retained on a 4.75-mm (No. 4) sieve for Method A or B, and 30 percent or less retained on a 19.0-mm (3/4-in.) sieve for Method C or D. Soil particles retained on these sieves are considered oversize particles.

If the test specimen contains oversize particles and is used for field density compaction control, corrections must be made according to T 224 to compare the field density with the compacted specimen. The method specifies that a minimum percentage of oversize particles can be specified below which correction is not required. If no minimum percentage is provided, correction should be applied to samples with more than 5 percent oversize particles. If the specified maximum tolerances for oversize particles are exceeded, alternative compaction control methods must be used.