What does a standard proctor test determine?

A standard proctor test is a fundamental laboratory procedure used in soil science and geotechnical engineering to determine the relationship between the moisture content of the soil and its dry density. Specifically, the test identifies the optimum moisture content at which the soil can achieve its maximum dry density when compacted. This information is crucial for construction projects and earthworks, as it helps engineers and contractors select appropriate moisture levels to ensure soil stability and structural integrity.

The process involves compacting a specific volume of soil at various moisture contents and measuring the resulting dry densities. The outcome of the test provides a compacted density curve that indicates the maximum dry density and the corresponding moisture content at which that density is achieved. Understanding these factors is critical for ensuring that the soil can adequately support structures and withstand loads over its lifetime. This makes identifying both soil density and optimum moisture content the correct focus of the standard proctor test.