Concrete Slump test Procedure | Applications | Types | Uses

Importance of Slump test are to check the workability of concrete. A good workable concrete has good strength.

What is Workability of Concrete ? 

It is the most important property of concrete due to which, there will be ease to mixed, transported & placed in position within a homogenous state. 

Workability of concrete mainly depends upon the following : quantity of water, aggregate grade as well as the % of fine materials in the mix. 

The following tests can be used to check the workability of concrete :

1. Slump test
2. Compaction factor test
3. Flow test
4. Kelly ball test
5. Vee-Bee consistometer test.
6. K-Slump Test

On site and lab, mainly Slump test  are performed, due to its ease and results. 

As a result, It gives quick result about the workability of concrete.

Slump Test: –

Slump test was very easy to perform this method. But these method, is not suitable for very wet or very dry concrete.
This test can be used as a control test, it is also an indication of the concrete uniformity from batch to batch. 

Repeated batches of the same mix, brought to the same slump.

This 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:-

The apparatus required for Slump test are listed below :

a. Mettalic Mould which is in the shape of frustum cone, 

b. tamping rod with bullet end, 

c. Scale or tape for measuring the slump. d.  Metallic sheet for placing Slump & trowel for pouring concrete in the slump.

1. Frustum Cone:- 
Frustum cone has two different diameters one at the top & other at the bottom. The dimensions of Frustum cone is mentioned in below table :-

2. Tamping rod:-
The rod having  Dia of 16mm & bullet end at one side. The height of tamping rod should be 0.6m long.

Slump test Procedure :-

1. Before, starting the test, we should clean the inner surface of Frustum cone & it should be free from moisture content and adherence of any old set concrete.
2. Now, we have to place the Cone on the metallic steel plate or on any smooth surface.
3. We have now to Fill the cone with concrete in four layers each with an approximate height of 1/4th of the mould.
4. Each layer should be tamped 25 times with tamping rod. We have to take care to distribute the strokes evenly on each part.
5. Now after filling the 4th layer, the excess concrete is struck off with the trowel.
6. After the mould completely filled, then the mould removed from the concrete immediately in a vertical direction by raising it slowly and carefully.
7. This allows the concrete to subside. This we know as SLUMP.

Result:-

1. Now, we have to measure the height of the mould & highest point of the slump in mm.
2. The difference between the Height of the mould and highest point of the Subside gives the Slump value.

To learn about the quantity of Cement, sand and aggregate used for Different grades of concrete, click here. 

Slump test values for Different Concrete Mixes:- 

Slump test values for Different Concrete Mixes:- 

Below are the Different Types of Slump in Concrete are listed below :-

1. True Slump :- 

If Concrete Slumps evenly forms a shape same as a mould then we called it as true slump.

2. Shear Slump:-

If half of the slump is slides or falls down then it is called as Shear Slump. 

This is the indication of that concrete is non-cohesive and have characteristics of segregation.

3. Collapse Slump:-

In these case, the c if the whole slump falls down in all directions & does not maintain the shape of mould, then it is called as Collapse slump. 

This Slump formed due to addition of excessive amount of water in concrete to increase the workability.

4. Zero Slump:- 

This test doesn’t suitable for Dry and Stiff concrete. For very Dry & high stiff concrete does not show any difference after removing the mould.

Limitations:-

1. Slump test cannot be performed, if the aggregate used in concrete is above 40mm size.
2. This test is not suitable for very dry & high stiff concrete.

Advantages:-

1. Slump test procedure can be performed in laboratory as well as construction site.
2. Slump test requires less apparatus, when compared with the other tests.
3. Time required for the results will be less as compared to other tests. 

Watch Video of the Slump test of concrete .

Video 1 :

Video 2 :

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