Proctor compaction test modified by American standards

6 Proctor compaction test (modified) by American standards 

The proctor compaction test defines the relationship between soil density and moisture content with the aim of determining the maximum density at a certain moisture content, known as the optimum moisture content. 

According to ASTM D 1557 (2012) or AASHTO T 180 (2010), a sufficient mass of soil material is mixed well with water, is transferred to a mould and is compacted by a dropping rammer. The mass of the rammer is 4.54 kg and the height of the drop is 457.2 mm. The term modified test is used since the standard mass of 2.5 kg and the drop height have been 

Modification was necessary since the development and use of heavier rollers resulted in higher site densities than laboratory densities at even lower optimum water content. The phenomenon is observed mostly in cohesive soils. Table 1.5 shows the differences observed between a standard and a modified proctor when specimens were compacted in the laboratory using either compaction method. 

6 mm mould is used only when the percentage retained on the 4.75 mm sieve is less than 7%. However, the 152.4 mm mould may be used in all cases. 

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