SLUMP TEST FOR CONCRETE :

SLUMP TEST FOR CONCRETE :

           

This method of test specifies the procedure to be adopted, either in the laboratory or during the progress of work in the field, for determining the consistency of concrete where the nominal maximum size of the aggregate does not exceed 38 mm.


The internal dimensions of the mould are ==>>

bottom diameter = 200 mm, top diameter = 100 mm, and height = 300 mm.


The mould is filled in with fresh concrete in four layers, each approximately one-quarter of the height and tamped with twenty-five strokes of the rounded end of the tamping rod. The strokes are distributed in a uniform manner over the cross-section and for the second and subsequent layers should penetrate into the underlying layer. The bottom layer is tamped throughout its depth. After the top layer has been rodded, the
concrete is struck off level with a trowel or the tamping rod, so that the mould is exactly filled. The mould is removed immediately by raising it slowly and carefully in a vertical direction. This allows the concrete to subside and the slump is measured immediately by determining the difference between the height of the mould and that of the highest point of the specimen being tested.

The slump measured is recorded in terms of millimetres of subsidence of the specimen.

==>>  Some indication of the cohesiveness and workability of the mix can be obtained , if after the slump measurement has been completed , the side of the concrete is tapped gently with the tamping rod , a well proportioned concrete of an appreciable slump will gradually slump further , but if the mix has been badly proportioned , it is likely to fall apart..


==>>The test is performed with maximum size of aggregate as 38 mm only. however if the aggregate size is larger the concrete is wet sieved through 38 mm screen to exclude aggregate particles bigger than 38 mm...