Importance of Slump Test in the Construction

The Slump Test is perhaps the most widely used because of the simplicity of the apparatus required and the test procedure. The slump test indicates the behavior of a compacted concrete cone under the action of gravitational forces. The slump test is a practical means of measuring the workability. Changes in the value of slump obtained during a job may indicate changes in materials in the water content or in the proportions of the mix. So it is useful in controlling the quality of the concrete produced.

The test carried out with a mould called the slump cone. The slump cone is placed on a horizontal and non absorbent surface and filled in three equal layers of fresh concrete. Each layer being tamped 25 times with a standard tamping rod. The top layer is struck off level and the mould is lifted vertically without disturbing the concrete cone.  The subsidence of concrete in millimeter is termed the slump. After the test, slumps evenly all around is called true slump.

In the case of very lean concrete, on half of the cone may slide down the other which called a shear slump or it may collapse in case of very wet concretes. The slump test is essentially a measure of consistency or the wetness of the concrete.

There are recommended slump for every concrete usage. Below are the table used to qualify a concrete mix.