Why is the slump of concrete important and how is a slump test done?

[Quest Bot]

Why is the slump of concrete important and how is a slump test done?

 

[amd007]

Why is the slump of concrete important and how is a slump test done?

Slump Test of any Concrete is used to test its workability and to get a rough idea of water-cement ratio of concrete.

Workability is defined as the ease with which the concrete can be transported, compacted and placed without any segregation(separation of water and aggregates separately).

The procedure of Slump Test :

1.First, clean the inner surface of the empty mould and then apply oil to it.

2. Set the mould on a horizontal non-porous and non-absorbent base plate.

3. Fill the mould fully by pouring freshly mixed concrete in three equal layers.

4. Stroke each layer 25 times with the standard tamping rod over the cross-section.

5. After stroking 25 times the top layer is struck off level, now lift the mould slowly in the vertical direction without disturbing the concrete cone.

6. Use the measuring scale to measure the difference level between the height of the mould and the concrete sample.

7. The subsidence of concrete is known as the slump and the value of slump is measured in mm.

True Slump: The concrete mass after the test when slumps evenly all around without disintegration is called the true slump.

Shear Slump: When one-half of the concrete mass slide down the other is called the shear slump. This type of slump is obtained in a lean concrete mix.

Collapse Slump: When the sample is collapsed due to adding excessive water, it is known as collapse slump.

Zero Slump: For very stiff or dry mixes it does not show any changes of the slump after removing the slump cone.

Recommended Values Of Slumps For Different Concrete Mixes:

Types Of Concrete	Slump Range In mm
1. Heavy mass construction	25-50
2. Pavements	20-30
3. Bridge deck	25-75
4. Beams and slabs	50-100
5. Columns, retaining walls and thin vertical members, etc.	75-150
6. Vibrated concrete	12-25