Slump test of concrete procedure by slump cone is required to check the correct amount of water has been add to concrete mix. Slump test is like consistency test of fresh concrete.
What is Slump Test
The concrete slump test measures the consistency of fresh concrete. We perform this slump test to check the workability of freshly made concrete, and the ease with which concrete flows. We can also use it as an indicator of an improperly mixed batch. The test is popular because of simplicity of apparatus used and procedure. The slump test is used to ensure uniformity and flow of concrete.
Although it is very easy to perform this method. But the slump test is not suitable for very wet or very dry concrete. It does not measure all factors contributing to workability and concrete place-ability.
We can use this test as a control test of the concrete uniformity from batch to batch. Repeated concrete batches of the same mix, brought to the same slump, will have the same water content and water cement ratio, weights of aggregate, cement and admixtures are uniform and aggregate grading is within acceptable limits.
Apparatus Required for Slump Test
1. Slump cone with base plate
Slump cone is a metal cone with open edges on both ends. Thickness of the cone metal shall be minimum 1.6 mm with clean and plain inner surface.
Dimension of Slump cone is given below:
Height – 300 mm
Upper or Top dia – 100 mm
Lower or Bottom dia – 200 mm
2. Slump rod or Temping rod
Slump rod shall be made with stainless steel.
Dimension of Slump rod is given below:
Length – 600 mm
Dia – 16 mm
We will use the trowel to mix the concrete sample before slump testing.
Use the enamel tray or any non absorbent tray for mixing the concrete sample before testing.
Type of Slump
There are three type of slump as per IS Code which we can find out during slump testing.
1. Collapse slump
In this slump type, concrete collapses on slump cone base plate after raising the slump cone. After determining the slump test when we get the slump value of any type of concrete mix 200 mm or more than 200 mm. Its called collapse slump of the relative concrete mix.
2. True slump
In this slump type, concrete just subsides shortly and more or less maintain the mould shape. This type of slump is most desirable and good for structure.
3. Shear slump
In this slump type, concrete slides down one-half of the cone in an inclined plane, it is called a shear slump. It is an indication of lack of cohesion of the mix or segregation.
Zero slump is not mentioned in IS Code
Sampling Concrete Mix for Slump Test
Slump test shall be done if maximum size of aggregate is less than 38 mm in concrete mix. If 40 mm aggregate used, Sieve the concrete sample through 38 mm sieve and take passed concrete for slump test.
Slump Test Procedure
- Clean every equipment which is going to be used for slump test such as slump cone, base plate etc.
- Take concrete sample in a tray for slump test after a proper mixing.
- Check that slump cone is proper tighten with base plate using nut and bolts.
- Inner surface of slump cone should be in wet condition for test but not watery.
- Mix the concrete mix in tray by using trowel.
- Place the slump cone attached with base plate on a plain and firm ground.
- Pour the concrete mix in slump cone near about one fourth height of cone ( around 75 mm ).
- Give 25 strokes throughout the mix poured in slump cone by using slump rod.
- Then pour again the nearly same quantity of concrete mix in slump cone and temp 25 times throughout the mix.
- Repeat the same procedure.
- In forth layer pour the concrete mix up to top level of slump cone.
- Temp 25 times and struck of the extra mix available on the top by trowel.
- Level the top surface by using trowel or temping rod as a straight edge.
- Clean the base plate if any mortar leaked form the joint between base plate and slump cone.
- Loose the nut or bolt by which you tighten the slump cone with base plate. While performing this action one person must hold the slump cone firmly so slump cone shall not be raise automatically.
- Raise the slump cone to straight vertically form ground.
Measuring the Slump
- Immediately after raising the slump cone check the difference between height of slump cone and top height of concrete.
- Perform this test in two minutes from the time of concrete sample taken.
- Measure the slump in only millimeter.
- If you observed shear slump then repeat the test.
Slump Test Result
|Sr. no||Transit mixer no.||Slump ( mm )||Slump type|
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