“The Standard Proctor Test is a laboratory test used to determine the optimum water for a given compaction energy, for a given soil. The graph illustrates the results obtained from a Standard Proctor test.
The Proctor compaction test is a laboratory method of experimentally determining the optimal moisture content at which a given soil type will become most dense and achieve its maximum dry density. (Compaction is the process by which the bulk density of an aggregate of matter is increased by driving out air.) The term Proctor is in honor of R. R. Proctor, who in 1933 showed that the dry density of a soil for a given compactive effort depends on the amount of water the soil contains during soil compaction.