The slump test is the most simple workability test for concrete, involves low cost & provides immediate results. Generally, concrete slump value is used to find the workability, which indicates water-cement ratio, but there are various factors including properties of materials, mixing methods, dosage, admixtures, etc. also affect the concrete slump value.
Apparatus:-
- Mould for slump test ( from a frustum of a cone having 30cm, bottom diameter 20cm, and top diameter 10cm)
- Non-porous base plate
- Measuring scale
- Tamping rod (steel rod 16mm diameter and 60cm height & rounded at the end )
- The internal surface of the mould was cleaned & oil was applied
- The mould was placed on a smooth horizontal non-porous base plate
- The mould was filled with the prepared concrete mix in 3 approximately equal layers
- Each layer was tamped with 25 strokes of the rounded end of the tamping rod in a uniform manner over the cross-section of the mould
- The excess concrete was removed and the surface was levelled with a trowel
- Clean away the mortar or water leaked out between the mould & the base plate
- The mould was raised from the concrete immediately & slowly in the vertical direction
- True slump – It is only slumped that can be measured in the test the measurement is taken between the top of the cone & the top of the concrete after the cone has been removed
- Collapsed slump – It is an indication that the water-cement ratio is too high. E.g. concrete mix is too wet or it is high workability mix, for which a slump test is not appropriate
- Shear slump – the shear slump indicates that the results is incomplete & concrete to be retested
