This standard outlines the procedure for determining the relationship between the moisture content and dry density of soils using heavy compaction, often referred to as the Modified Proctor Test. It is crucial for determining the maximum dry density (MDD) and optimum moisture content (OMC) required for heavy-duty earthworks like highways and dams.
Describes the procedure for determining the optimum moisture content and maximum dry density of soil using the heavy compaction (Modified Proctor) test.
Quick Reference Values
rammer weight4.9 kg
rammer drop height450 mm
number of layers5
blows per layer 1000cc mould25
blows per layer 2250cc mould56
standard mould volume1000 cc
large mould volume2250 cc
Key Formulas
Bulk Density (γb) = (M2 - M1) / V
Dry Density (γd) = 100 * γb / (100 + w) — where w is moisture content in percent
Practical Notes
Ensure the soil is properly mixed with water and allowed to mature (cure) in an airtight container before testing to ensure uniform moisture distribution, especially for highly plastic clays.
Use the larger 2250 cc mould instead of the standard 1000 cc mould if the soil sample contains a significant percentage of coarse material retained on the 4.75 mm IS sieve.
For soils that are susceptible to crushing during compaction, a separate batch of soil must be used for each data point on the compaction curve.