What is slump flow?
Slump flow is the average diameter in millimetres over which very fluid fresh concrete spreads after a filled cone is lifted. The test is mainly used for self-compacting concrete. In Dutch it is called vloeimaat or uitvloeimaat.
How is slump flow measured?
The test is set out in EN 12350-8:
- Place the cone (the same shape as in the slump test) on a flat, damp and rigid base plate.
- Fill the cone in one go with fresh concrete, without rodding or vibrating.
- Lift the cone steadily and vertically.
- Let the concrete flow freely until it stops.
- Measure the largest diameter of the spread and the diameter at right angles to it. The average is the slump flow.
The difference from the flow table test: in the flow table test the table top is lifted and dropped fifteen times, while in the slump flow test the concrete flows under its own weight only.
Classes
EN 206 contains three slump flow classes for self-compacting concrete:
| Class | Slump flow (mm) |
|---|---|
| SF1 | 550 – 650 |
| SF2 | 660 – 750 |
| SF3 | 760 – 850 |
The higher the class, the more fluid the mix. SF1 suits simple, lightly reinforced elements; SF3 suits slender, heavily reinforced structures.
What to look out for
- Spot segregation: after the test, look at the edge of the spread. A ring of only cement paste or water, or coarse aggregate left in the centre, indicates segregation.
- Additional tests: slump flow says nothing about how the mix passes through reinforcement. The J-ring test and the V-funnel time are used for that.
- Level base: a sloping or dry plate gives a deviating result.
Related terms
- Flowing concrete
- Flow table test
- Consistency class
- J-ring test
- V-funnel time
- Fresh concrete
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