There are three types of slump that may occur in slumps test, namely, true slump, shear slump and collapse slump.
True slump refers to general drop of the concrete mass evenly all around without
disintegration.
Shear slump implies that the concrete mix is deficient in cohesion. Consequently, it may undergo segregation and bleeding and thus is undesirable for durability of concrete.
Collapse slump indicates that concrete mix is too wet ad the mix is deemed to be harsh and lean.