What does the Proctor test determine?

The Proctor test is a fundamental procedure in soil mechanics that primarily determines the optimal moisture content and the maximum dry density of soil. This is essential for understanding how a particular soil sample will behave under various conditions, particularly when it comes to construction and earthworks.

During the Proctor test, soil is compacted at different moisture content levels, and measurements of density are taken. The results create a curve that illustrates the relationship between moisture content and dry density, allowing engineers to identify the point where the maximum dry density occurs at a specific moisture content. This is crucial for achieving optimal compaction in construction projects, ensuring that the soil provides adequate support for structures and prevents issues like settling or shifting.

While the other options pertain to different properties of soil—such as organic material content, permeability, and plasticity—these are not the focus of the Proctor test. The test is specifically designed to assist in achieving optimal compaction, making option B the clear choice.