About slump cone test in concrete

Concrete Slump Test for Workability -Procedure and Results. Concrete slump test is to determine the workability or consistency of concrete mix prepared at the laboratory or the construction site during the progress of the work.

Procedure for Concrete Slump Test:

• Clean the internal surface of the mould and apply oil.
• Place the mould on a smooth horizontal non- porous base plate.
• Fill the mould with the prepared concrete mix in 4 approximately equal layers.
• Tamp each layer with 25 strokes of the rounded end of the tamping rod in a uniform manner over the cross section of the mould. For the subsequent layers, the tamping should penetrate into the underlying layer.
• Remove the excess concrete and level the surface with a trowel.
• Clean away the mortar or water leaked out between the mould and the base plate.
• Raise the mould from the concrete immediately and slowly in vertical direction.
• Measure the slump as the difference between the height of the mould and that of height point of the specimen being tested.

 Types of Concrete Slump Test Results

True Slump – True slump is the only slump that can be measured in the test. The measurement is taken between the top of the cone and the top of the concrete after the cone has been removed as shown in fig

Zero Slump – Zero slump is the indication of very low water-cement ratio, which results in dry mixes. These type of concrete is generally used for road construction.

Collapsed Slump – This is an indication that the water-cement ratio is too high, i.e. concrete mix is too wet or it is a high workability mix, for which a slump test is not appropriate.

Shear Slump – The shear slump indicates that the result is incomplete, and concrete to be retested.