Mixes and slump
Slump explained: how stiff or fluid a mix should be
Slump measures how workable fresh concrete is, which decides how easily it’s placed, compacted and finished. Select a class to see what each one is typically used for.
S1
10–40 mm
Road kerbs, pipe and drainage bedding, stiff mixes
Slump classes
S1 to S5 at a glance
Slump is measured with a cone test: the cone is filled with fresh concrete and lifted away, and the drop in height is the slump. On a volumetric truck the slump can be changed on site, part-way through a pour.
Select a row to see it in the explorer above.
| Class | Slump | Typical applications |
|---|---|---|
| S1 · Low | 10–40 mm | Road kerbs, pipe and drainage bedding, stiff mixes |
| S2 · Medium | 50–90 mm | Foundation footings, slabs, general-purpose floors |
| S3 · Medium-high | 100–150 mm | Trench-fill foundations, paving in tight spaces |
| S4 · High | 160–210 mm | Floor slabs, formwork, pumping in confined areas |
| S5 · Very high | 220 mm or more | Pumped concrete for piling and difficult ground |
Inside the truck
What goes into a cubic metre of our C20
These are the quantities from our own trials and calibration by Volumech Technical Services. The truck measures them out as it mixes.
- Cement
- CEM I 52.5N, from Hanson or Heidelberg Materials: pure Portland cement, not a blended CEM II
- Sand
- 0/4 washed sand
- Stone
- 4/20 limestone, so the mix has every particle size from 0 to 20 mm
Why adding water isn’t the answer
The water-to-cement ratio decides how strong the concrete ends up. Extra water makes a mix easier to place, but it weakens the concrete and raises the risk of cracking. For a more workable mix, the better option is additional cement or a water-reducing admixture.
Mix families
- Standard mixes, C10 to C30
- General residential and commercial work: driveways, patios and foundations.
- Specialised mixes, C35 to C50
- Structural elements, industrial floors and heavy-duty infrastructure.
- Mixes with admixtures
- Fibres, plasticisers and water reducers for freeze-thaw, chemical exposure or heavy traffic.
- Custom mixes
- Designed with you for jobs that need specific properties.
Tell us the job and we’ll match the mix
Foundations, a pump mix and a floor screed can all come off one truck on the same day.