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OMC-SP and MDD-SP denote the optimum moisture content and maximum dry density obtained from the standard Proctor compaction test, respectively. OMC-MP and MDD-MP denote the optimum moisture content and maximum dry density obtained from the modified Proctor compaction test, respectively. Which one of the following is correct?

1. OMC-SP < OMC-MP and MDD-SP < MDD-MP
2. OMC-SP > OMC-MP and MDD-SP < MDD-MP
3. OMC-SP < OMC-MP and MDD-SP > MDD-MP
4. OMC-SP > OMC-MP and MDD-SP > MDD-MP

Correct answer: OMC-SP > OMC-MP and MDD-SP < MDD-MP

Solution

In the modified Proctor test, the compactive effort is higher than in the standard Proctor test. Higher energy generally increases maximum dry density and decreases optimum moisture content. Therefore OMC-SP > OMC-MP and MDD-SP < MDD-MP.

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