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
  • Ashish February 2, 2010 at 12:25 am

    In general,at what slump value should the concrete cubes be casted at the site if it is coming from a RMC manufacturer. Any specific standards mentioned for the same. If not, if the cubes are casted at a higher slump say 150mm&above or at a relatively lower slump say 100mm&below what effectit will have on the 3,7,&28 days compressive strength of concrete of any grade.

    • pavani August 30, 2010 at 2:30 pm

      slump is an imp factor in testing of cubes..and slum for residential buildings nearly 80..n slump shall not be less than 60 in any case..and also slum ‘ll be nearly 180 at the time of piling work is done..because for piling more water is requred..

  • fami February 12, 2010 at 10:12 am

    1. what is the importance of slump test in concrete work?
    2. what is the definition of segregation and bleeding in concrete mixture?

  • Syfirah March 6, 2010 at 11:03 pm

    What are the significances of 7 days and 28 days compressive strength??

  • anuj kumar March 29, 2010 at 4:44 am

    how the slump is related to strength of concrete.

    • Chong August 3, 2010 at 12:40 pm

      Slump is never related to strength of concrete. Slump determines the WORKABILITY of concrete.

      The 3, 7 or 28 day compressive test determines the strength of concrete.

      • rosli January 5, 2012 at 4:19 am

        agreed.that slump is never related to strength..The w/c determine the strength..
        with latest admixture technology..u still get the required strength with any slump/flow..

  • Muhammad Tasawar March 31, 2010 at 12:53 am

    thats good information

  • Joshua April 13, 2010 at 3:11 pm

    I am a student form federal polytechic nekede owerri,building technology department, i want to be one you people that is make it.i love you all that care for me

  • arpita das April 24, 2010 at 3:39 am

    value of slamp test of M20 concrete?

  • asb April 24, 2010 at 5:46 am

    thx for the work

  • dhanasekar April 26, 2010 at 1:50 am

    what is the slump value in good result of bridges…
    and which grade concrete is best in construction of tallest buildings…

  • satyajit April 29, 2010 at 4:18 am

    why slump test is important for concrete

    • Ravi July 12, 2010 at 6:27 am

      The concrete slump test is, in essence, a method of Becoz,quality control. For a particular mix, the slump should be consistent. A change in slump height would demonstrate an undesired change in the ratio of the concrete ingredients; the proportions of the ingredients are then adjusted to keep a concrete batch consistent. This homogeneity improves the quality and structural integrity of the cured concrete.

  • Sudeep Mukherjee May 28, 2010 at 3:39 am

    What will be the maximum limit of slump for Driven cast in situ piling works?

    • pavani August 30, 2010 at 2:36 pm

      it shall be 180

  • Aneesh May 29, 2010 at 7:14 am

    it shall not be more than 150

  • pyy June 2, 2010 at 10:24 pm

    what are the limitations of the slump test?
    will the addition of measured water to a ready concrete mix gave the desired water/cement ratio?
    why is the slump test suitable for site use?

  • biruk June 7, 2010 at 1:56 am

    that is a good test

  • anandhi June 15, 2010 at 3:19 am

    Dear sir in ideal value of slum for M25 mix

  • Navjeet Singh June 20, 2010 at 6:44 am

    Dear sir what is the ideal value of slum for M25 mix

    • Vishal March 3, 2013 at 1:50 am

      0 slump

  • kvs babu July 5, 2010 at 2:52 am

    Dear sir,

    What cement chemical and physical perameters are influencing the slump. As our cements initial slump is 170mm after 30 min it is 80mm. how to improve this.

  • DJONG July 21, 2010 at 2:59 pm

    Explain why the slump test is the most commonly used consistence.
    A concrete mix is found to segregate easily.Describe the steps that can be taken to improve cohesiveness.
    Explain what caused the cracking and what could have been done to prevent it.
    what is the compaction factor of concrete that is completely self compacting

    • Chong August 3, 2010 at 12:33 pm

      The slump test is commonly used to assess the workability of the mixture. It is the fastest (and cheapest) way to gauge the consistency of the concrete batches used for placement in structural works. It is NOT a test to gauge the strength of concrete (The typical 3, 7 or 28-day compressive test does that).

      A concrete mix found to segregate easily is likely to be too “wet”. Possible solutions are: (1) reduce the water-cement ratio; and (2) if admixtures (superplasticizers) are used, reduce the amount.

      Compaction factor of concrete that is completely self compacting = 1.0 (ie, Weight of partially compacted concrete = Weight of fully compacted concrete).

  • G.Achchuthan August 19, 2010 at 4:41 am

    sir, why is the test done and the frequency at which it is done at site?

  • hemant kushwah September 16, 2010 at 1:57 am

    what is the ratio of water cement and conceret for M 20 ???

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