Slump test and it's Needs in Civill engineering

Slump test is used to measure the workability of fresh concrete. It’s a simple and most popular test. Click the link below to know about slump test.

Apparatus used in test:

• Cone (300mm x 200mm x 100mm)

• Measuring scale

• Tamping rod

Procedure of slump test:-

1. Internal surface of the cone should be cleaned properly and a light coat of oil should be applied.
2. Cone should be placed on a horizontal place
3. The cone is then filled with freshly mixed concrete in 3 layers.
4. Each layer is tamped 25 times by the tamping rod.
5. After filling the cone properly, the cone is removed from the concrete immediately by raising it slowly in the vertical direction.
6. After removing the cone subsided concrete is measured
7. The slump of the concrete = height of the cone – height of the subsided concrete.

Types of Slump:-

The slump is termed as three types

     

                                         1) Collapse slump  2) Shear Slump  3)True Slump

If the Slump is termed as shear or collapse slump, a fresh sample should be taken and the test repeated.

Result of Slump Test

0 – 25 mm = very dry mixes = used in road making.

10 – 40 mm = low workability mixes = used for foundations with light reinforcement

50 – 90 mm = medium workability mixes = used for normal reinforced concrete

100+ mm high workability concrete.

Limitation of the slump test:

The slump test is suitable for slumps of medium to high workability, slump in the range of 25 – 125 mm. The test fails to determine the difference in workability in stiff mixes which have zero slump. Or for wet mixes that give a collapse slump. It is limited to concrete formed of aggregates of less than 38 mm.