How to slump test concrete consistency and why it’s important
The concrete slump test is required to measure consistency of fresh concrete before it sets. This test is paramount to check the workability of freshly made concrete, and therefore the ease with which concrete flows.
Concrete Testing can be used as an indicator of an improperly mixed batch of concrete. Slump testing is particularly popular due to the simplicity of the test and apparatus. The slump test is used to ensure uniformity for different loads/batches of concrete under field conditions.
Concrete workability is distinguished by the slump measurement of the mixed concrete. Different applications require different consistencies of concrete which is shown in the below table.
| Class | Slump range (mm) | Target slump (mm) |
| S1 |
10 - 40 |
20 |
| S2 |
50 - 90 |
70 |
| S3 |
100 - 150 |
130 |
| S4 |
160 - 210 |
180 |
| S5 |
210 - n/a |
220 |
S1 - Stiff, can give immediate support to kerbs or drainage works
S2 - Normal workability
S3 - Mid-range workability. Optimum for placing, compaction and finishing
S4 - Trench fill workability
S5 - Very workable, but where the slump test is not a suitable measure of workability