The concrete slump can be classified according to the nature of concrete fall. There are 3 types of the slump. These are:
- True slump: In a true slump concrete just subsides shortly and more or less maintain the mould shape. This type of slump is most desirable.
- Shear slump: If one-half of the cone slides down in an inclined plane, it is called a shear slump. Shear slump indicates lack of cohesion in the concrete mix. Shear slump may occur in the case of a harsh mix.
- Collapse slump: In this case, fresh concrete collapses completely.
Zero Slump: If concrete maintains the actual shape of the mould, it is called zero slump which represents stiff, consistent and almost no workability.
The true slump is the only reliable condition to get an idea about the workability of concrete. If other types occur, the test should be repeated.