Generally a concrete mix is required to provide a specified degree of workability, although there is no general agreement on how workability should be defined. Workability is often considered to be a measure of the work needed to compact the wet concrete, but it is also used to quantify the ease with which concrete can be placed, although this depends on other properties such as cohesiveness.
Workability is usually measured by the Slump Test, but Firstmix also provides the option of specifying the required workability with a Vebe Time Test.
Some typical values of reasonable slumps and Vebe times are shown below.
| Type of Construction | Suitable slump | Suitable Vebe time | ||||
| mm | In. | Seconds | ||||
| Min | Max | Min | Max | Max | Min | |
| Uncongested precast concrete | 0 | 25 | 0 | 1 | - | 12 |
| Power vibrated pavements | ||||||
| Mass concrete | 0 | 50 | 0 | 2 | - | 4 |
| Slabs | 25 | 75 | 1 | 3 | 2 | 8 |
| Footings | ||||||
| Uncongested walls | ||||||
| Columns | 25 | 100 | 1 | 4 | 1 | 7 |
| Beams | ||||||
| Normally reinforced walls | ||||||
| Congested narrow sections | 100 | 175 | 4 | 7 | 0 | 2 |
The required workability is stored in mix files as both a slump value and a Vebe time. The levels of workability defined in the DOE Method give both Slump values and Vebe times for each level, and these values are used in Firstmix for converting between Slump values and Vebe times.