Which test is used to determine the maximum dry density used for percent compaction?

• A. Proctor test
• B. Atterberg limit test
• C. California bearing ratio test
• D. Sieve analysis

Answer: (A)

Determining the maximum dry density used for percent compaction comes from a compaction test that simulates drilling in the field at different moisture contents. The Proctor test does this by compacting soil in a mold with a specific energy and measuring the resulting dry density across a range of moisture contents. The highest point on that curve is the maximum dry density, and the moisture content at that peak is the optimum moisture content for compaction. Those values let you calculate percent compaction for the project.

The other tests mentioned serve different purposes: Atterberg limits assess soil plasticity and liquidity; the California bearing ratio tests bearing capacity; and sieve analysis checks particle size distribution.