Workability of Fresh Concrete by Slump Test

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WORKABILITY
Slump test is used to determine the workability of fresh concrete. Slump test as per IS: 1199 – 1959 is followed.The apparatus used for doing slump test are Slump cone and Tamping rod.

Procedure to determine workability of fresh concrete by slump test.
i) The internal surface of the mould is thoroughly cleaned and applied with a light coat of oil.
ii) The mould is placed on a smooth, horizontal, rigid and nonabsorbent surface.
iii) The mould is then filled in four layers with freshly mixed concrete, each approximately to one-fourth of the height of the mould.
iv) Each layer is tamped 25 times by the rounded end of the tamping rod (strokes are distributed evenly over the cross section).
v) After the top layer is rodded, the concrete is struck off the level with a trowel.
vi) The mould is removed from the concrete immediately by raising it slowly in the vertical direction.
vii) The difference in level between the height of the mould and that of the highest point of the subsided concrete is measured.
viii) This difference in height in mm is the slump of the concrete.

slump-test-fresh-concrete

Reporting of Results
The slump measured should be recorded in mm of subsidence of the specimen during the test. Any slump specimen, which collapses or shears off laterally gives incorrect result and if this occurs, the test should be repeated with another sample. If, in the repeat test also, the specimen shears, the slump should be measured and the fact that the specimen sheared, should be recorded.

Typical Questions
Ques 1. What is the ideal value of slump?
Answer 1
In case of a dry sample, slump will be in the range of 25-50 mm that is 1-2 inches. But in case of a wet concrete, the slump may vary from 150-175 mm or say 6-7 inches. So the value of slump is specifically mentioned along the mix design and thus it should be checked as per your location.

Slump depends on many factors like properties of concrete ingredients – aggregates etc. Also temperature has its effect on slump value. So all these parameters should be kept in mind when deciding the ideal slump

Ques 2. How does a superplasticizer effect the slump of concrete?
Answer 2
Value of Slump can be increased by the addition of chemical admixtures like mid-range or high-range water reducing agents (super-plasticizers) without changing the water/cement ratio.

Ques 3. How much time one should take to raise the cone?
Answer 3 Once the cone is filled and topped off [ excessive concrete from top is cleared ] raise the cone within 5-10 seconds.

Ques 4. What are the dimensions of the cone used in Slump Test?
Answer 3
The dimensions are
Top Diameter – 10cm
Bottom Diameter – 20cm
Height – 30cm

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Comments
  • Manoj Bhola August 22, 2012 at 8:39 am

    What will be the slump value for column,slab,Retaining wall,footing,piers?

  • hirwa February 10, 2013 at 3:01 am

    for slump test must known the workability of concrete bt we tolk. about compression test

  • Ajit kumar sahu. March 8, 2013 at 3:04 pm

    The slump value of concrete should be lie between 25mm to 125mm.

  • vm sounthararajan March 14, 2013 at 6:00 am

    if i used pumping of concrete with steel fibres, any slump losss there or not

  • Pritish Gupta April 17, 2013 at 1:44 pm

    How to do determine the slump of a concrete. Who tells you which slump is appropriate and why?

  • Manoj kumar May 7, 2013 at 6:49 am

    What is the reason if slump of a mix for design comes approximately same after 30 min.and 60 min.?

  • kry sok heng July 8, 2013 at 12:42 am

    i want the appropriate slump value for casting the precast T-girder.

  • vikas.Patil January 11, 2014 at 7:52 am

    At 120mt what type of do we use

  • SURENDAR March 18, 2014 at 9:52 am

    what is proportion of mix for conducting slump test

  • alex July 22, 2014 at 2:11 am

    good……thanks…..

  • Samsul Islam September 1, 2014 at 8:06 am

    What is VEBE Consistometer and Specifications Limits…

  • Post a comment

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