SLUMP TEST - Printable Version

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SLUMP TEST - C M Dordi - 06-22-2022

SLUMP TEST
Taken from : Ambuja Technical  Literature Series -20

INTRODUCTION
It is very essential for concrete to have good workability so that entrapped air can be easily removed by minimum effort of compaction. In field conditions it is often observed that workability may vary from batch to batch due to many reasons. The most common reasons being batching error of water, presence of surface moisture· on aggregates and absorption of water by dry aggregates. However variation in grading and shape of the aggregates can also cause workability variations even if water addition and surface moisture are properly controlled. Even though it is the prime responsibility of the mixer operator to ensure production of concrete of uniform quality and workability from batch to batch, it is equally important to check regularly that correct workability is obtained by using a proper test. Slump test for workability is the simplest test and is most often used at
construction sites and must be carried out using the apparatus complying to IS 7320-1974.


SLUMP TEST
In this test the distance that a conefull of concrete slumps down is measured when the cone is carefully lifted from around it. The concrete slumps can vary from zero for dry (stiff) mixes to complete collapse for very wet and lean mixes. This test is not very accurate for very stiff mixes and therefore the compaction factor test is generally used. However unless absolutely necessary very stiff mixes are not desirable and quite often not used. Therefore, compaction factor test is not described in this booklet: The accuracy of the slump test is generally Umited to within about 25 mm of the intended value when workability of each batch is compared with earlier batches.

USEFULNESS OF SLUMP TEST

This test can serve as an indication for three factors :

a) If grading of aggregates are uniform it will indicate variations of water content or water/cement ratio.


b) If amount of water added to the mix is accurate and surface moisture of fine aggregates is constant then it will indicate variations in grading
or variations in batching of cement or aggregates.

c) If the cohesiveness of the mix for a particular workability is not adequate, due to inadequate concrete mix design and batching, the concrete cone
will collapse or shear off. 


for more detail download ..... 

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RE: SLUMP TEST - Manish Jain - 06-22-2022

FREQUENCY OF THE SLUMP TEST
It is important to do this test preferably in the first batch as soon as the concreting work starts. This is necessary so that correct water addition is
finalised to give the required workability. Thereafter this test is performed whenever the mix does not seem to be right and adjustment of water is
desirable.
Slump test is also necessary for every batch of concrete sampled for cube test so that in case of cube failure some conclusions can be drawn whether
the mix had more workability or in other words it had higher W/C than that of the recommended mix.
The slump test must be taken as soon as possible at about the same time after mixing.

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