Compaction Tests (“Maximum Density” or “Proctor”)

Add to Cart

Course Material(0.47MB, PDF) You need Adobe Reader to view and print the Course Material. (Get Adobe Reader)

Course Synopsis:

Soil Compaction Tests are frequently called “Maximum Density” or “Proctor” tests, with their names interchangeable.  Specifications typically call for a Standard Proctor or a Modified Proctor, and usually specify a test method designation such as ASTM D698, for example.  Sometime both are used, varying with the design requirements.  Standard Proctors provide less compactive effort than Modified Proctors.  Modified Proctor tests of the same soil will yield a higher maximum density and lower optimum moisture content.

Proctor tests are performed in the laboratory to determine the maximum density, in dry pounds per cubic foot, of the tested soil and its corresponding optimum moisture that is practically achievable in the field.  Field in-place density tests are then performed and compared to the “Proctor” maximum density to determine the percentage of the proctor.  For example, if the Maximum Density/Proctor dry density is 130.0 pcf and the field density test is 125.5 dry pcf, the in-place “% of proctor” is 125.5/130.0 = 96.5%.  Typically, project specifications require the soil to be compacted to some percentage, usually 95% -100% of a Standard or Modified Proctor. 

This course explains the purpose, equipment, procedures, and result determination methods of the Corps of Engineer’s Compaction Tests methods.  Very similar, but slightly different, are the ASTM D698 and AASHTO T-99 “Standard” Proctor methods and the ASTM D1557 and AASHTO T-180 are “Modified” Proctor methods.  Various agencies’ specifications normally contain requirements citing either the Corps, ASTM, or AASHTO maximum density Proctor methods.  Engineers should be familiar with all of these methods and their nuances.

It is imperative that the specified, published test method be strictly followed.  Otherwise, the results may be deemed invalid, resulting in potentially significant cost to the company or agency performing the tests.  There is essentially no room for mistaken test methods or procedures.  Shortcuts are not acceptable.

Course Objectives:

This course teaches the following specific knowledge and skills regarding Compaction Tests (“Maximum Density” or “Proctor”): 

  • Differing types of Compaction Tests and procedures depending on soil gradation results

  • Required equipment, soil sample size, and sample preparation procedures

  • Compaction, weighing, drying, and calculation procedures

  • Recording, plotting, and determining the maximum density and optimum moisture


CivilPDH is an approved PDH course provider. 

View Resources »