Slum
test is the most commonly used method of measuring consistency of concrete
which can be employed either in laboratory or at site of work. The apparatus
for conducting the slump test essentially consists of a metallic mould in the
form of a frustum of a cone having the internal dimensions as under:
Bottom Diameter : 20
cm
Top diameter : 10 cm
Height : 30 cm
For tamping the concrete, a steel tamping rod 16
mm die, 0.6 meter along with bullet and is used. The mould is placed on a
smooth,horizontal,rigid and non – absorbent surface.The mould is then filled in
four layers,each approximates ¼ of the height of the mould.Each layer tamped 25
times by the tamping rod taking care to distribute the strokes evenly over the
cross section.After the top layer has been rodded,the concrete is stuck 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 the concrete to subside.Th 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 is measured. The difference in
height in mm .is taken as Slump of Concrete.
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