The most common method for determining the fluidity of concrete is the slump test. During this test, the concrete mix is placed in three layers into a standard-sized conical slump cone. Each layer is compacted with a 16mm diameter rod, vertically and uniformly jabbed from the outside inward 25 times. After compaction, the surface of the mixture in the cone is smoothed, and the cone is then lifted vertically and set aside. Due to its own weight, the mixture will slump; the measurement of the slump (in mm) indicates the fluidity of the concrete. A larger slump value indicates greater fluidity.

The slump test is only suitable for plastic and low-plasticity concrete; for dry-hard concrete, the workability is often measured using a Vebe consistometer.

1. The concrete mix is placed in three layers, each compacted with 25 stabs. After compacting, the surface is smoothed, and the slump cone is lifted vertically and steadily.

• Dry-hard: Slump (mm) 0-60, Workability (s) 60-120
• Semi-dry-hard: Slump (mm) 0-30, Workability (s) 30-60
• Low-plasticity: Slump (mm) 10-50, Workability (s) 15-30
• Plastic: Slump (mm) 50-150, Workability (s) 5-15
• Fluid: Slump (mm) >150

The selection of concrete slump or workability level should be based on the method of forming, cross-sectional size, and the density of the reinforcement.