The 'compaction energy' in the modified Proctor test (IS 2720 Part 8) is higher than standard because:
Choose the correct answer
Standard Proctor uses heavier rammer
Modified uses 4.5 kg rammer + 457 mm drop in 5 layers — 4.5× energy representing heavy field compaction equipment
Modified test uses same energy but different soil
Both tests have identical energy levels
Correct Answer
B. Modified uses 4.5 kg rammer + 457 mm drop in 5 layers — 4.5× energy representing heavy field compaction equipment
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Standard Proctor (IS 2720 Part 7): 2.5 kg rammer, 305 mm drop, 3 layers, 25 blows = 596 kJ/m³. Modified Proctor (IS 2720 Part 8): 4.5 kg rammer, 457 mm drop, 5 layers, 25 blows = 2700 kJ/m³ (4.5× higher). Higher energy → higher MDD, lower OMC. Used for: heavily compacted base courses, airfield pavements. Modified corresponds to compaction achieved by heavy rollers in field.
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