Heavy Compaction Test (Modified Proctor)

The heavy compaction (modified Proctor) test follows the same principle as the light compaction test but uses a heavier 4.9 kg rammer, a greater drop height and five compacted layers, giving a substantially higher compactive effort.

It is used where field compaction plant applies more energy than the standard test represents — typically highway subgrade, embankment fill and airfield pavement works — so that laboratory OMC/MDD values realistically match what can be achieved on site.