How to test slump

Cone and rod in a slump test

The procedure is as follows:

  1. The cone is positioned on the base plate with the smaller aperture uppermost
  2. Freshly supplied concrete is poured into the cone to approximately one-quarter of its depth (75mm)
  3. The concrete is tamped using 25 strokes of the steel rod
  4. Further concrete is added to fill the cone to approximately one-half depth (ie: another 75mm of concrete)
  5. Again, the concrete is tamped using 25 strokes of the rod
  6. More concrete is added to bring up the level to three-quarter depth (another 75mm)
  7. 25 strokes using the rod are used to tamp down the concrete
  8. The cone is filled to the top and tamped using a final 25 strokes with the steel rod
  9. A final trowelful or two of concrete is added to bring it level with the top of the cone
  10. The cone is carefully lifted upwards, clear of the concrete and is placed, upside-down next to the concrete
  11. After a minute or so, the unrestrained concrete will settle downwards or "slump" due to gravity
  12. The steel rod (or other suitable straightedge) is used to span the inverted cone and towards the slumped concrete
  13. The height difference between the steel cone and the slumped concrete is measured
  14. This difference, measure to the nearest 10 millimetres, is "The Slump"

Measuring the height of the slumpExample slumping of the main concrete consistencies