What is the purpose of Slump Test and explain the procedure of the testing?

Slump test is the most commonly used method of measuring workability of concrete
which can be employed either in laboratory or at site of work.

Procedure
The mould is placed on a smooth, horizontal,rigid and non-absorbant surface The mould is then filled in four layers, each approximately 1/ 4 of the height of the mould. Each layer is
tamped 25 times by the tamping rod taking Slump Test Apparatus care to distribute the strokes evenly over the cross section. After the top layer has been rodded,the concrete is struck off level with a trowel and tamping rod. The mould is removed from the concrete immediately by raising it slowly and carefully in a vertical direction. This allows theconcrete to subside. This subsidence is referred as SLUMP of concrete. The difference in level
between the height of the mould and that of the highest point of the subsided concrete ismeasured. This difference in height in mm is taken as Slump of Concrete.