Which test determines compaction density in base materials?

Which test determines compaction density in base materials?

• A. Permeability
• B. Atterberg Limits
• C. Piezometer Test
• D. Proctor Density

Answer: (D)

Understanding how tightly a base material can be packed is what this item tests. The Proctor Density test is specifically designed to determine the maximum dry density achievable for a soil and the moisture content at which that density occurs. In this test, a soil sample is compacted in a standardized mold using a defined energy in layers, then weighed to compute dry density. Repeating the process across different moisture contents builds a compaction curve, from which the maximum dry density and its corresponding optimum moisture content are identified. This information guides field compaction—ensuring the base layer reaches its designed density for structural strength. The other tests measure different properties: permeability checks how easily water moves through the material, Atterberg Limits assess plasticity, and a piezometer measures pore-water pressure, none of which directly determine compaction density.

Understanding how tightly a base material can be packed is what this item tests. The Proctor Density test is specifically designed to determine the maximum dry density achievable for a soil and the moisture content at which that density occurs. In this test, a soil sample is compacted in a standardized mold using a defined energy in layers, then weighed to compute dry density. Repeating the process across different moisture contents builds a compaction curve, from which the maximum dry density and its corresponding optimum moisture content are identified. This information guides field compaction—ensuring the base layer reaches its designed density for structural strength. The other tests measure different properties: permeability checks how easily water moves through the material, Atterberg Limits assess plasticity, and a piezometer measures pore-water pressure, none of which directly determine compaction density.