Concrete Slump Test Procedure

 Concrete Slump Test Procedure

Step 1

Firstly, the internal surface of the mould is cleaned carefully. Oil can be applied on the surface.

Step 2

The mould is then placed on a base plate. The base plate should be clean, smooth, horizontal and non-porous.

Step 3

The mould is filled with fresh concrete in three layers. Each layer is tamped 25 times with a steel rod. The diameter of this steel rod is 5⁄8 inch. The rod is rounded at the ends. The tamping should be done uniformly.

Step 4

After filling the mould, excess concrete should be removed and the surface should be leveled. When the mould is filled with fresh concrete, the base of the mould is held firmly by handles.

Step 5

Then the mould is lifted gently in the vertical direction and then unsupported concrete will slump. The decrease in height at the center point is measured to nearest 5mm or 0.25 inch and it is known as ‘slump’.

Cautions Required During Concrete Slump Test

To get the proper result, some cautions must be taken during the test. Following are the list of major caution that can be maintained. 

• Inside of the mould and base should be moistened before every test. It is necessary to reduce surface friction.
• Prior to lifting mould, the area around the base of the cone should be cleaned from concrete which may be dropped accidentally.
• The mould and base-plate should be non-porous.
• This test should be performed in a place free of vibration or shocks.
• The concrete sample should be very fresh, the delay must be avoided and the test should be done just after mixing.

Measurement of workability from the Slump Test

If shear slump or collapse slump occurs, the test should be repeated. We can get the result from the only true slump. We can classify the result within some ranges according to the slump value.

1. Very low workability: slump value 0-25mm or 0-1 inch
2. Low workability: slump value 25-50mm or 1-2 inch
3. Medium workability: slump value 50-100mm or 2-4 inch
4. High workability: slump value 100-175mm or 4-7 inch

According to 'Fresh Concrete' by P. Bartos, slump results can be classified as given below:

1. No slump: slump value 0 mm or 0 inch
2. Very Low: sump value 5-10 mm or 0.25-0.5 inch
3. Low: sump value 15-30 mm or 0.75-1.25 inch
4. Medium: sump value 35-75 mm or 1.5-3 inch
5. High: sump value 80-155 mm or 3.25-6 inch
6. Very High: sump vaue180 mm or 6.25 inch to collapse

According to European Standard ENV 206: 1992, workability is classified in 4 categories of S1, S2, S3, and S4. Slump ranges are:

• S1: 10-40 mm
• S2: 50-90 mm
• S3: 100-150 mm
• S4: more than 160 mm

Though there are different types of workability classification, the main rule is that low slump value indicates less workability and high sump value indicates high workability.