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1. The inside surface of the mould is carefully cleaned and applied with a light coat of oil.
2. The mould is positioned on a horizontal, smooth, rigid and nonabsorbent surface.
4. Every layer is tamped 25 times by the rounded end of the tamping rod (strokes are distributed uniformly over the cross section).
5. After the peak layer is rodded, the concrete is struck off the level with a trowel.
7. The variation in level between the height of the mould and that of the highest point of the subsided concrete is calculated.
8. This diversity in height in mm is the slump of the concrete.
The slump measured should be recorded in mm of subsidence of the specimen during the assessment. Any slump specimen, which collapses or shears off laterally, gives wrong result and if this occurs, the test should be repeated with another sample. If, in the repeat test also, the specimen shears, then slump should be measured and the fact that the specimen sheared, should be recorded.
MEASUREMENT OF SLUMP
Slump
test is used to decide the work-ability of fresh concrete. Slump test as per IS:
1199 – 1959 is followed. The equipment used for doing slump test is Slump cone
and tamping rod.
Method
to determine workability of fresh concrete by slump test;
1. The inside surface of the mould is carefully cleaned and applied with a light coat of oil.
2. The mould is positioned on a horizontal, smooth, rigid and nonabsorbent surface.
3. The mould is then packed in four layers with newly mixed concrete, each approximately to one-fourth of the height of the mould.
4. Every layer is tamped 25 times by the rounded end of the tamping rod (strokes are distributed uniformly over the cross section).
5. After the peak layer is rodded, the concrete is struck off the level with a trowel.
6. The mould is removed from the concrete instantly by raising it gradually in the vertical direction.
7. The variation in level between the height of the mould and that of the highest point of the subsided concrete is calculated.
8. This diversity in height in mm is the slump of the concrete.
Reporting of outcome
The slump measured should be recorded in mm of subsidence of the specimen during the assessment. Any slump specimen, which collapses or shears off laterally, gives wrong result and if this occurs, the test should be repeated with another sample. If, in the repeat test also, the specimen shears, then slump should be measured and the fact that the specimen sheared, should be recorded.
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