Slump Test of Concrete as per Indian Standard (IS 1199: 1959)

Slump Test of Concrete as per Indian Standard (IS 1199: 1959)

Aim
To determine the workability (consistency) of fresh concrete by conducting a slump test in accordance with IS 1199:1959.

Apparatus

1. Slump Cone: A metallic cone with a height of 300 mm, a bottom diameter of 200 mm, and a top diameter of 100 mm.
2. Base Plate: A flat, non-absorbent surface on which the cone is placed.
3. Tamping Rod: A 16 mm diameter, 600 mm long metal rod with a rounded end.
4. Measuring Scale: For measuring the slump height.
5. Scoop: For filling the concrete into the cone.

Theory
The slump test is a simple method to assess the workability or consistency of fresh concrete before it is placed in molds. Workability refers to the ease with which concrete can be mixed, placed, and compacted without segregation. The degree of workability influences the concrete's strength, durability, and surface finish.

Concrete with higher workability will have a higher slump value. The slump test is widely used at construction sites to ensure the quality of concrete mixes, especially in terms of water-cement ratio, as improper workability can lead to segregation, bleeding, or honeycombing.

There are three types of slumps:

• True Slump: The concrete maintains its shape and collapses slightly.
• Shear Slump: The concrete slides down one side.
• Collapse Slump: The concrete collapses completely.

Procedure

1. Preparation of the Sample:
   Mix the concrete as per the required proportions for the test. Ensure that the sample is fresh and homogenous.

2. Filling the Slump Cone:

   • Place the slump cone on a flat, non-absorbent base.
   • Fill the cone with fresh concrete in three layers, each approximately one-third of the height of the cone.
   • After placing each layer, compact it with 25 blows using the tamping rod. Distribute the blows evenly across the surface.
   • Continue filling and compacting each layer until the cone is full.

3. Leveling and Removing the Cone:

   • After filling the cone and compacting the final layer, level the top of the cone using the tamping rod.
   • Lift the cone vertically in one smooth motion without disturbing the concrete.

4. Measuring the Slump:

   • The concrete will slump due to its weight. Measure the vertical difference between the top of the slump cone and the highest point of the slumped concrete.
   • Record the slump in millimeters.

Observation Table

Sample No.	Initial Height (mm)	Final Height (mm)	Slump (mm)	Type of Slump
1	300	250	50	True Slump
2	300	180	120	Collapse Slump
3	300	270	30	True Slump

Sample Readings

• Initial height of the cone: 300 mm
• Final height of the slumped concrete: 250 mm
• Slump = Initial height - Final height $$\text{Slump} = 300 \, \text{mm} - 250 \, \text{mm} = 50 \, \text{mm}$$

Reporting the Results
The slump value obtained is reported in millimeters, along with the type of slump observed. For instance:

• Slump = 50 mm (True Slump)
• Slump = 120 mm (Collapse Slump)

As per Indian Standards, the acceptable slump value for different types of concrete work varies:

• Low slump (25–50 mm): Used for low workability concrete like those for foundations.
• Medium slump (50–100 mm): Suitable for general-purpose concrete such as beams, slabs, and columns.
• High slump (100–150 mm): Used in concrete requiring high workability, such as those with congested reinforcement.

Conclusion
The slump test helps assess the workability of concrete on-site. The sample readings in this test indicated a slump of 50 mm, representing a true slump, meaning that the concrete has moderate workability, which is suitable for general construction purposes. Based on the results, the mix was neither too stiff nor too fluid, making it ideal for typical applications like beams and slabs. Adjustments in the water-cement ratio may be required if the slump does not fall within the desired range for the specific application.