The operation of removing humps and hollows from a freshly placed concrete surface is known as:
Correct Answer: B. Screeding
📚 Detailed Explanation: Screeding — Removing Humps and Hollows
Why B (Screeding) is correct: Screeding is the first step in concrete surface finishing. A long straight-edge board (screed board or darby) is placed across the surface and moved forward with a sawing or zigzag motion to strike off excess concrete, fill low spots, and create a uniformly levelled surface.
How Screeding Works
| Feature | Detail |
|---|---|
| Tool | Straight-edge screed board (2–4 m long); darby; mechanical screed |
| Motion | Sawing or zigzag across the surface; moved progressively forward |
| Purpose | Remove humps; fill hollows; set surface to required grade |
| When done | Immediately after concrete placement and consolidation (vibration) |
Floor Finishing Sequence with Operations
| Step | Operation | Removes/Creates |
|---|---|---|
| 1 | Screeding | Removes humps and hollows; establishes level |
| 2 | Floating | Removes screed marks; embeds aggregate; closes surface |
| 3 | Troweling | Creates final hard, smooth, dense surface |
- Screeding = first finishing step; removes humps and hollows; uses a straight-edge board.
- Floating comes after screeding; troweling comes last.
- Mechanical (vibrating) screeds combine screeding and initial compaction for road pavements.