According to IS 5515, the distance between the bottom of the lower hopper and the top of the cylinder in the Compacting Factor Apparatus is:
Try it first: pick an option, then read the explanation.
Correct answer: D. 20.0 cm
Detailed Explanation: Compacting Factor Apparatus Dimensions (IS 5515)
The Compacting Factor test (IS 1199) measures workability by comparing the degree of compaction achieved with a standard amount of work. IS 5515 specifies the precise dimensions of the apparatus.
Why D (20.0 cm) is correct: The Compacting Factor Apparatus consists of two conical hoppers stacked above a cylinder. The critical dimensions per IS 5515 are:• Upper hopper bottom to lower hopper top = 20.3 cm
• Lower hopper bottom to cylinder top = 20.3 cm ≈ 20.0 cm
This standardised gap ensures concrete falls from a consistent height, providing reproducible partial compaction. Options A (22.9 cm = 9 in), B (25.4 cm = 10 in), and C (12.7 cm = 5 in) are not the correct dimension for this specific gap.
Compacting Factor Apparatus Key Dimensions
| Dimension | Value |
|---|---|
| Upper hopper: top diameter | 25.4 cm |
| Upper hopper: bottom diameter | 12.7 cm |
| Lower hopper: top diameter | 22.9 cm |
| Lower hopper: bottom diameter | 12.7 cm |
| Cylinder: diameter × height | 15.2 cm × 30.5 cm |
| Lower hopper bottom to cylinder top | ≈ 20.0 cm |
- Compacting Factor (CF) = Mass of partially compacted concrete / Mass of fully compacted concrete.
- CF = 0.80–0.85 (low), 0.85–0.92 (medium), >0.92 (high workability).