Slump is the measure of concrete workability. Select slump based on placement method, member type, and reinforcement density. Higher slump = more workable but may reduce strength if achieved by adding water instead of admixture.
Notes
• NEVER increase slump by adding water — use admixture (plasticizer/superplasticizer)
• Adding 1 litre of water per m³ increases slump ~25mm but reduces strength by ~1–2 MPa
• Slump test: fill cone in 3 layers, 25 strokes each, remove cone vertically, measure settlement
• True slump = cone settles evenly; Shear slump = one side falls (retest); Collapse = too wet
• Test frequency: one slump test per batch or per 2 m³ (whichever is less)
• In hot weather (>35°C), target higher initial slump as concrete loses workability during transport
• Retempering (adding water at site) is NOT permitted per IS 456