Engineering Materials·MCQ explained

Compaction factor for heavily reinforced section with vibration is .............

Try it first: pick an option, then read the explanation.

Correct answer: D. > 0.92

Detailed Explanation: Compaction Factor for Heavily Reinforced Sections

Why D (>0.92) is correct: Heavily reinforced sections have closely spaced rebars that restrict concrete flow. Even with vibration, the fresh concrete must be fluid enough to reach all parts of the formwork before vibration consolidates it. A CF > 0.92 (high workability) ensures this. Lower CF values give stiffer mixes that would leave voids around dense reinforcement even with vibration.

Compaction Factor vs. Application

Compaction FactorWorkabilityTypical Application
<0.75Very lowDry lean concrete
0.75–0.85LowRoads, pavements (vibrated)
0.85–0.92MediumNormal RCC (slabs, beams)
>0.92HighHeavily reinforced sections
  • CF > 0.92 = high workability required for congested reinforcement zones.
  • Vibration does NOT replace workability requirements — it complements them.