Which statement describes the purpose of Proctor testing in density control?

• A. It measures color of soil
• B. It predicts weather patterns
• C. It establishes maximum dry density and optimum moisture content used as reference for field compaction
• D. It determines the price of earthwork materials

Answer: (C)

Proctor testing is used to determine how dense soil can become and at what moisture level that maximum density occurs. By compacting soil samples at several moisture contents, you identify the moisture content that yields the highest dry density—the optimum moisture content. Those two values become the reference for field compaction: you condition the soil to near the optimum moisture content and apply compaction energy to achieve a dry density close to the maximum. This ensures the fill has adequate strength and stability, while avoiding under- or over-compaction. It’s not about color, weather predictions, or material pricing.