Slump cone test to find out Workability

Tests used to find out Workability of a freshly mixed concrete are:

1. Slump cone test
2. Vee bee test
3. Compaction factor test

Slump test is performed on freshly mixed concrete to find out the water content and workability or consistency of concrete. The test is useful in controlling quality of the concrete.

Equipments: Non-absorbent base plate, trowel, steel tamping rod( 16mm diameter and length is 600mm), slump cone or Abrams cone( base dia.200mm, top dia. 100mm and height 300mm), ruler.

Materials: Mix design 1:2:4 and water- cement ratio: 0.50

Cement: 2.5kg

Sand: 5kg

Coarse aggregate: 10kg

Water: 1.25kg

Procedure:

• Place the cone on Non-absorbent base plate having small dia. section at upper side.
• Pour the freshly mixed concrete into the cone in three layers (i.e. each layer of 100mm.)
• Now each layer is tamped for 25 times using tamping rod.
• Now level the top surface of cone with trowel.
• Now lift the cone upwards with slight rotation of cone.
• After lifting the concrete either it fall or stand. The height of falled concrete due to gravity is called slump.
• The difference in between height of moulded cone and the height after subsidence of concrete is measured which is called as slump of the concrete.

Discussion:

• If you get zero slump then repeat the test to get the true slump with different water-cement ratio and mix design.
• The slump test is useful to ensure uniformity under field conditions for different batches of same concrete.
• If obtained slump is collapse slump then reduce water-cement ratio.

Types of slump:

• True slump
• Shear slump
• Collapse slump

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