AASHTO T99

Full Name

AASHTO T99 – Standard Method of Test for Moisture-Density Relations of Soils Using a 2.5-kg (5.5-lb) Rammer and a 305-mm (12-in.) Drop

Scope

AASHTO T99 is a standard test method used to determine the relationship between the moisture content and density of soils when compacted with a specific energy. This test, often called the “Modified Proctor” test, is essential for geotechnical engineering and construction projects to optimize soil compaction and ensure the stability and performance of earthworks, embankments, and foundations.

Key aspects of AASHTO T99:

  • Purpose: the primary objective is to establish the optimal moisture content (OMC) at which a soil achieves its maximum dry density (MDD). Compacting soil at OMC ensures the highest level of stability and load-bearing capacity for the intended application.
  • Test procedure: the test involves compacting soil specimens at various moisture contents into a mold of a given size using a 2.5-kg (5.5-lb) rammer dropped from a height of 305 mm (12 in.). The dry density of each compacted specimen is determined, and a graph plotting dry density versus moisture content is constructed. The peak of the curve indicates the OMC and MDD.
  • Four alternative methods: the standard offers four alternative methods based on the soil type and the desired level of compaction:
    1. Method A: 101.60-mm (4-in.) mold for soil passing a 4.75-mm (No. 4) sieve.
    2. Method B: 152.40-mm (6-in.) mold for soil passing a 4.75-mm (No. 4) sieve.
    3. Method C: 101.60-mm (4-in.) mold for soil passing a 19.0-mm (3/4-in.) sieve.
    4. Method D: 152.40-mm (6-in.) mold for soil passing a 19.0-mm (3/4-in.) sieve.

Significance of AASHTO T99:

  • Geotechnical design: the moisture-density relationship obtained from this test is crucial for designing compacted earth fills, embankments, and subgrades for roads, airports, and other structures.
  • Quality control: contractors use this test to verify that the soil compaction on the construction site meets the specified density requirements, ensuring the stability and performance of the earthwork.
  • Material selection: the test results help evaluate the suitability of different soils for specific applications based on their compaction characteristics and potential for achieving the desired density.

AASHTO T99 Accredited Laboratory

Applied Testing & Geosciences, LLC is accredited for performing tests using the AASHTO T99 standard.

Our laboratory offers comprehensive soil testing services, including the determination of moisture-density relations according to AASHTO T99. Our experienced technicians utilize calibrated equipment and adhere to standardized procedures to provide accurate and reliable results for your geotechnical projects.

Contact us for more information.

Resources

Keywords

moisture-density; relations; soils; compaction; maximum; density; optimum; moisture content; test; procedure; apparatus; mold; rammer; drop; sieve; sample; weighing; calculation; report; oven

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