Consistency Class

Concrete Slump Test or Consistency Class

Slump-Cone-Test-ApparatusThe concrete slump test is a test that measures the workability of fresh concrete. More specifically, it measures the consistency of the concrete. Consistency is directly related to workability. It is a term which describes the state of fresh concrete as it is delivered to site. It refers to the ease with which the fresh concrete can flow. The slump test is used to indicate the degree of wetness or workability of the concrete. The wetter mixes will be more workable than drier mixes, but concrete of the same consistency may vary in workability.

The slump test is popular due to the simplicity of apparatus used and simple procedure.


EN 206-1 currently has five Consistency classes with slump ranges as follows;

Slump class Slump in mm
S1  Dry  (Kerb backing, dry fill and sloping slabs etc.) 10 – 40
S2   Standard (Foundations, Slabs and other general structures) 50 – 90
S3   Wet (Foundations, slabs, Pumping concrete) 100 – 150
S4   Very Wet (Foundations, slabs, Pumping and Piling concretes) 160-210
S5   Self Levelling (Foundations, slabs, Pumping and Piling concretes) ≥220

slump-test01It should be noted that the wetter the concrete the weaker the strength will be for a given mix design. This can be counteracted by increasing the cement content, however, this may increase the cost on some concrete mixes.