| Primary value | 75 – 100 mm (Abrams cone slump test) |
| Applies to | RCC slabs (cast in-situ) · RCC beams · Conventional vibrated concrete with normal-strength mixes (M20–M30) |
| Exceptions | Slumping by 25 mm = ↓ ~2 N/mm² strength → Adding 4 L water / m³ for 25 mm slump |
| Pumped concrete → 100 – 150 mm | |
| Self-compacting concrete (SCC) → 550 – 750 mm flow (not slump) | |
| Measured as | True slump = vertical drop of cone-shaped fresh concrete from the 300 mm-tall Abrams cone after demoulding. Measured at the centre of the slumped specimen. |
| Source | IS 1199 (Part 2) — Clause 5 ✓ Verified |
68 related items across IS codes, knowledge articles, design rules, maps and tools
Slump is the cheapest workability check on site — 75–100 mm gives the placement rheology that vibrated slabs and beams need without bleeding excess paste to the surface. Higher slump increases bleed, plastic shrinkage, and reduces strength. The IS 456 dilution rule (4 L water = 25 mm slump = −2 N/mm²) is the conversion every site mixer rejection should reference.
Indian batching plants supply M25 / M30 with 100 ± 25 mm slump for slab work. Site-mixed concrete tends to be wetter (120–150 mm) than design — the cube test is the only sanity check that catches it.