Part 2 is the slump test — the most-used workability/consistency check. Using the IS 7320 cone, fill in three layers with 25 rod strokes each, strike off, lift vertically in 2–5 s, and measure the slump to the nearest 5 mm. Interpret true vs shear vs collapse slump; its real value is as a batch-to-batch consistency trend that flags added water or aggregate-moisture changes.
Key Requirements
•Apparatus per IS 7320 (cone 200/100/300 mm, 16 mm tamping rod), non-absorbent base
•Fill in 3 layers, 25 rod strokes per layer; strike off; lift cone vertically in 2–5 s, no twist
•Measure slump (drop of the highest point) to the nearest 5 mm; re-test on shear/collapse
•Slump is a comparative consistency index, not strength — use the trend to catch added water/agg-moisture change
•Test on a representative sample (Part 1) at the relevant point (placement)
Reference Tables
Slump types
Result
Meaning / action
True slump
Concrete settles evenly — valid result
Shear slump
One side slides off — re-test; recurring = harsh mix
Collapse slump
Mix collapses — too wet/harsh; re-test, investigate
Confirm procedure/tolerances against the current IS 1199 Part 2 edition.
Practical Notes
✓Slump's job is to catch change — a jump usually means added water or wetter aggregate, not a cone problem (provided the IS 7320 cone is standard).
✓Never add site water to 'restore' slump — fix workability via the mix/admixture (cf. IS 9103), not the hose.
Common Mistakes
⚠Battered/non-standard cone or stick instead of the 16 mm rod (trend becomes noise).
⚠Twisted/tilted cone lift (false slump).
⚠Treating slump as a strength/quality verdict instead of a consistency trend.