Which of the following method may be used for getting a more workable concrete?
Correct Answer: A. By increasing cement content
📚 Detailed Explanation: Methods to Increase Workability
Why A (Increasing cement content) is correct: At a constant w/c ratio, adding more cement increases total paste volume. The paste (cement + water) lubricates the aggregates and fills voids between them. More paste = better lubrication = higher workability. Options B, C, and D all reduce workability:
B: Lower w/c = stiffer, less fluid paste.
C: Angular aggregates have higher surface friction and interlock, impeding flow.
D: Smaller aggregates = higher total surface area = more water needed for the same workability.
B: Lower w/c = stiffer, less fluid paste.
C: Angular aggregates have higher surface friction and interlock, impeding flow.
D: Smaller aggregates = higher total surface area = more water needed for the same workability.
Effect on Workability
| Change | Effect on Workability |
|---|---|
| Increase cement content (const. w/c) | Increases |
| Decrease w/c ratio | Decreases |
| Angular aggregates (replace rounded) | Decreases |
| Reduce aggregate size | Decreases |
- Higher paste volume = better lubrication = higher workability.
- Other workability improvers: add water (increases w/c), use rounded aggregates, add plasticiser.