Proctor tests in FDOT density requirements establish which values are used as a reference for field compaction?

• A. Dry density only
• B. Optimum moisture content only
• C. Maximum dry density and optimum moisture content
• D. Field compaction equipment settings

Answer: (C)

Proctor tests give a relationship between dry density and moisture content for a soil. The highest point on that curve is the maximum dry density, and the moisture content at that point is the optimum moisture content. In FDOT density requirements, those two values define the reference state for field compaction. The goal in the field is to achieve a specified percentage of that maximum dry density at moisture conditions around the optimum. This makes the density target meaningful because density changes with moisture, and the optimum moisture content is where compaction is most efficient. Using only dry density would ignore how moisture affects compaction, and using only optimum moisture content would ignore the actual achievable density. Equipment settings are tools to reach the target, not the reference values themselves.