Slump Test

The required Slump Test value may be entered in the ’Slump’ field on a Mix Design Form.

The slump test is the simplest and most commonly used test for workability.

The freshly mixed concrete is packed into a 300 mm (12 in.) high cone, 200 mm (8 in.) wide at the bottom and 100 mm (4 in.) wide at the top, which is open. The concrete is smoothed off level with the top rim of the cone, and the cone is then carefully lifted, so that the concrete is left unsupported. The slump is the distance that the centre of the cone top settles. In a so-called ‘true’ slump test the base of the concrete does not spread excessively. If the concrete collapses or shears to one side the test results will be unreliable.

Although the slump test does not directly measure the work needed to compact the concrete, it gives a reasonable indication of the how easily a mix can be placed and is simple to perform. The test is only suitable for reasonably workable, cohesive mixes. Very stiff mixes do not settle enough for useful measurements to be made and uncohesive mixes tend to shear or collapse. A slump of less than 25 mm (1 in.) indicates a stiff concrete and a slump of more than 125 mm (5 in.) indicates a very runny concrete.

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.

  • See Method of Specifying Workability for selecting to use the Slump or Vebe tests
  • Range: 0 - 175mm(7 in.).