The height of a slump cone mould used for testing the workability of the concrete is 30 cm.

The slump test is used to test the workability of concrete. Since the workability of concrete increases, to a certain extent, with the amount of water added, the slump test can also serve as a test to control the water content in a concrete mix. The test is done by compacting a sample of concrete in a conical mould.

The mould has dimensions of 100 mm (10 cm) in diameter at the top, 200 mm (20 cm) in diameter at the bottom and 300 mm (30 cm) in height. The mould is then lifted vertically, allowing the concrete to subside or slump. The amount of slump below the original height of 300 mm (30 cm) is measured. This is taken as an index of the workability of the concrete.