INTRODUCTION
Slump test is most commonly used method to determine the workability or consistency of concrete mix.
This test can be employed in field as well as in laboratory. It is not suitable method for very dry or very wet mix. It does not measure all factors contributing to workability , nor is it always representative of the placability of concrete.
APPARATUS
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 : 200 mm
Top diameter : 100 mm
Height : 300 mm
For tamping the concrete,a steel tamping rod 16 mm diameter, 0.6 m along with bullet end is used.
PROCEDURE
The internal surface of concrete is thoroughly cleaned and freed from initial moisture and adhere of any old set concrete before.
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 mould as per IS 456 whereas in ASTM it is filled in three layers each of 1/3 height of mould by tampering each layer 25 times by distributing the strokes evenly all over the cross section of mould.
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 vertical direction. This allows the concrete to subside. This subside is referred as slump of concrete.
As per ASTM measure the centre of slumped concrete as the difference in the height whereas in IS 456 difference in height in mm after subside of concrete.
TYPES OF SLUMP
Slump test is most commonly used method to determine the workability or consistency of concrete mix.
This test can be employed in field as well as in laboratory. It is not suitable method for very dry or very wet mix. It does not measure all factors contributing to workability , nor is it always representative of the placability of concrete.
APPARATUS
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 : 200 mm
Top diameter : 100 mm
Height : 300 mm
For tamping the concrete,a steel tamping rod 16 mm diameter, 0.6 m along with bullet end is used.
PROCEDURE
The internal surface of concrete is thoroughly cleaned and freed from initial moisture and adhere of any old set concrete before.
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 mould as per IS 456 whereas in ASTM it is filled in three layers each of 1/3 height of mould by tampering each layer 25 times by distributing the strokes evenly all over the cross section of mould.
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 vertical direction. This allows the concrete to subside. This subside is referred as slump of concrete.
As per ASTM measure the centre of slumped concrete as the difference in the height whereas in IS 456 difference in height in mm after subside of concrete.
TYPES OF SLUMP
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