SLUMP TEST FOR WORKABILITY OF CONCRETE

SLUMP TEST OF CONCRETE 

In this article we will know about various type of slump, slump value of diffrent type of part of structure. Dear friend Slump test is very important on construction site. Question about slump is mostly asked in Interview.

SLUMP TEST: - Slump test is most commonly used test to determine the consistency of concrete. It can also be carried out at both the places, laboratory and site of work. It can be conveniently used as a control test and gives good indication of uniformity of concrete from batch to batch.

APPARATUS:-  

SLUMP CONE 

PROCEDURE: -  

1.       The internal surface of mould should thoroughly cleaned and made free from any kind of dust and moisture. The old concrete adhered from previous test should also be removed.

2.       The mould is placed on smooth horizontal, non-absorbent surface.

3.       The mould is filled with concrete in four equal layers. Each layer is tempted by a steel rod with 25 stroke to each layer.

4.       When mould is fully filled with concrete and last layer of concrete is tempted, the top surface of concrete is made level by removing off of the excess concrete with the help of tamping rod or trowel.

5.       Just in 5 second after mould is removed by lifting it vertically with the help of guide provided to mould, carefully and slowly. This allows the concrete to subsidise. This subsidence is referred as ‘Slump of Concrete’.

SLUMP PATTEREN OR TYPE OF SLUMP OCCURRED  

       Generally four types of slump occurred

·         True Slump: - If the concrete subsidise evenly, it is called true slump. Or if the value of slump comes as per specification then it is called True slump.

·         Shear Slump: - If one half of concrete cone slid down. It is called shear slump. The shear slump is measured as difference in height of cone and average value of subsidence. If the sample shows shear slump he experiment should be repeated. If again it shows shear slump then it should be recorded as shear slump.

Shear slump indicate the concrete is non cohesive or harsh and shows the characteristics of segregation. Also it indicated the poor grading of aggregates.

·         Collapse Slump: - It indicate a linear mix.

 Zero Slump :- Zero type of slump concrete occurs in  workable concrete which is practicly not easy                             to handle on site to vibrate or place the concrete. 

NOTE   :-  

1.                                 2o to 25mm for low workability.
2.                                 50-100mm for medium workability.
3.         100-150 mm for high workability. 

SOME OTHER IMPORTANT QUESTION ABOUT SLUMP

• Slump test is performed at batching plant before concrete is providing to site.

• Slump should be checked at site also just before pouring the concrete in structure.

• Slump value is decreased as temprature is increased.

• Slump test is performed in the presence of site in-charge, consultant engineer or in the presence of client.

Slump Test

SUGGESTED RANGES OF WORKABILITY OF CONCRETE (IS 456:2000)

RECOMMENDED SLUMPS FOR VARIOUS CONCRETE WORK