Compacting factor is defined as the ratio of –
Correct Answer: B. mass of partially compacted concrete to mass of fully compacted concrete
📚 Detailed Explanation: Definition of Compacting Factor
Why B is correct: CF = Wpartial / Wfull
The numerator is the mass of concrete in the cylinder after it has fallen through the two hoppers under gravity (partial compaction by its own weight).
The denominator is the mass of the same volume of fully compacted concrete (achieved by rodding/vibrating).
CF ranges from ~0.70 (very stiff) to ~1.0 (very fluid). High workability → gravity compaction approaches full compaction → CF closer to 1. Option A (fully/partially) is the inverse — that would give values >1, which is meaningless as a ratio.
The numerator is the mass of concrete in the cylinder after it has fallen through the two hoppers under gravity (partial compaction by its own weight).
The denominator is the mass of the same volume of fully compacted concrete (achieved by rodding/vibrating).
CF ranges from ~0.70 (very stiff) to ~1.0 (very fluid). High workability → gravity compaction approaches full compaction → CF closer to 1. Option A (fully/partially) is the inverse — that would give values >1, which is meaningless as a ratio.
CF Calculation Example
| Measurement | Example Value |
|---|---|
| Mass of partially compacted concrete (Wp) | 14.92 kg |
| Mass of fully compacted concrete (Wf) | 16.20 kg |
| CF = Wp/Wf | 0.92 (medium-high) |
- CF = partial / full (ratio ≤ 1.0). Higher CF = more workable.
- CF is more reliable than slump for stiff mixes where slump = 0.