These methods of test in AASHTO T99 are intended for determining the relation between the moisture content and density of soils compacted in a mold of a given size with a 2.5-kg (5.5-lb) rammer dropped from a height of 305 mm (12 in.). Four alternate procedures are provided as follows:
- Method A—A 101.60-mm (4-in.) mold: Soil material passing a 4.75-mm (No. 4) sieve Sections 4 and 5.
- Method B—A 152.40-mm (6-in.) mold: Soil material passing a 4.75-mm (No. 4) sieve Sections 6 and 7.
- Method C—A 101.60-mm (4-in.) mold: Soil material passing a 19.0-mm (3/4-in.) sieve Sections 8 and 9.
- Method D—A 152.40-mm (6-in.) mold: Soil material passing a 19.0-mm (3/4-in.) sieve Sections 10 and 11.
The method to be used should be indicated in the specifications for the material being tested. If no method is specified, the provisions of Method A shall govern.
AASHTO T99 applies to soil mixtures that have 40 percent or less retained on the 4.75 mm- (No. 4) sieve, when Method A or B is used and 30 percent or less retained on the 19.0-mm (3/4-in.) sieve, when Method C or D is used. The material retained on these sieves shall be defined as oversized particles (coarse particles).
If the test specimen contains oversize particles, and the test specimen is used for field density compaction control, corrections must be made according to AASHTO T 224 to compare the total field density with the compacted specimen density. The person or agency specifying this method shall specify a minimum percentage of oversize particles below which correction for oversize need not be applied. If no minimum percentage is specified, correction shall be applied to samples with more than 5 percent by mass of oversize particles.
If the specified oversized maximum tolerances are exceeded, other methods of compaction control must be used.