In a mix if the desired slump is not obtained, the adjustment for each concrete slump difference is made by adjusting water content by:
Correct Answer: B. 0.5%
📚 Detailed Explanation: Water Content Adjustment for Slump Correction
Why B (0.5%) is correct: IS 10262 (Guidelines for Concrete Mix Design) specifies: for every 25 mm change in slump, water content is adjusted by 0.5% of the total water content.
Example: If target slump = 75 mm, design water = 186 kg/m³, but measured slump = 50 mm (25 mm short):
Water correction = +0.5% × 186 = +0.93 kg/m³. Adjust accordingly and maintain the same w/c ratio by also adjusting cement proportionally.
Example: If target slump = 75 mm, design water = 186 kg/m³, but measured slump = 50 mm (25 mm short):
Water correction = +0.5% × 186 = +0.93 kg/m³. Adjust accordingly and maintain the same w/c ratio by also adjusting cement proportionally.
IS 10262 Slump Adjustment Rule
| Situation | Adjustment |
|---|---|
| Measured slump 25 mm below target | Increase water by 0.5% |
| Measured slump 25 mm above target | Decrease water by 0.5% |
| Per-mm rule | 0.5% water per 25 mm = 0.02% per mm |
- 0.5% water adjustment per 25 mm slump difference per IS 10262.
- Adjust cement proportionally to maintain the target w/c ratio.