How much time is allowed for lifting the slump mold?

• A. 1-3 seconds
• B. 3-7 seconds
• C. 8-12 seconds
• D. 15 seconds

Answer: (B)

The test relies on a controlled, consistent release of the mold so the measured slump reflects the concrete’s true workability, not the way the mold is removed. Lifting the slump mold over 3 to 7 seconds provides a smooth, vertical release that minimizes added energy or disturbance. If the mold is removed too quickly, the sudden release can push the concrete and create a larger slump than what the material would exhibit alone. If the removal is too slow, the concrete may continue to consolidate or the surface may begin to set, giving an artificially smaller slump. So, 3–7 seconds gives a balanced, reproducible release, which is why that range is the correct choice.