Light Compaction Test (Standard Proctor)

The light compaction (standard Proctor) test compacts soil into a mould in three layers using a 2.6 kg rammer falling from a fixed height, at a series of different moisture contents. Plotting dry density against moisture content gives a compaction curve, whose peak identifies the Optimum Moisture Content (OMC) and Maximum Dry Density (MDD).

These values are the reference point site compaction is checked against during earthwork — contract specifications typically require field density to reach a stated percentage (e.g. 95-98%) of the laboratory MDD.