| Primary value | 50 – 75 mm (Abrams cone slump test) |
| Applies to | RCC columns · RCC shear walls · Pedestals and short cantilever walls |
| Exceptions | Heavy reinforcement / congested cage → 75 – 100 mm |
| Tremie-placed concrete (piles, deep foundations) → 150 – 200 mm | |
| Mass concrete (gravity walls, raft pours) → 25 – 50 mm | |
| Measured as | Same Abrams-cone procedure as slabs. Lower target slump prevents segregation in the long vertical fall during column casting. |
| Source | IS 456 — Table 12, Clause 7.1 ✓ Verified |
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Vertical members face a different problem than horizontal ones — concrete free-falling 3 m from the chute segregates if the mix is too fluid, leaving aggregate at the bottom and paste at the top. 50–75 mm slump is dry enough to grip the cage and resist segregation but wet enough to consolidate around heavy reinforcement under needle vibration.
Most Indian sites pour columns at 75 mm slump and slabs at 100 mm — same batch, water adjusted by the supervisor at the chute. Tall column lifts ( > 3 m) need a tremie pipe or pump line to bypass the segregation problem entirely.