The Slump Test of Concrete is the most commonly used field test to check the workability and consistency of fresh concrete before placement.
It is simple, quick, and widely used on construction sites for quality control.
Why Slump Test Is Important
Slump test helps engineers to:
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✅ Check workability of concrete
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✅ Maintain uniform quality
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✅ Avoid segregation and bleeding
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✅ Ensure easy placing and compaction
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✅ Detect excess water in concrete
Applicable Standard
📘 IS Code: IS 1199 – Methods of Sampling and Analysis of Concrete
📘 Test Type: Field test (fresh concrete)
What Is Slump Test?
The slump test measures the vertical settlement (slump) of fresh concrete after removing the slump cone.
👉 More slump = higher workability
👉 Less slump = stiffer concrete
Equipment Required
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Slump cone (Abrams cone)
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Tamping rod (16 mm diameter, 600 mm length)
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Base plate (non-absorbent)
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Measuring scale
Dimensions of Slump Cone
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Top diameter: 100 mm
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Bottom diameter: 200 mm
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Height: 300 mm
Step-by-Step Slump Test Procedure
1️⃣ Preparation
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Clean the slump cone and base plate
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Wet the inner surface of the cone
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Place cone on a flat, non-absorbent surface
2️⃣ Filling the Cone
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Fill concrete in 4 equal layers
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Each layer is tamped 25 times using tamping rod
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Distribute strokes uniformly
3️⃣ Leveling
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Strike off excess concrete
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Level the top surface smoothly
4️⃣ Lifting the Cone
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Lift the cone vertically upward slowly
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Do not twist or jerk the cone
5️⃣ Measurement
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Measure the difference between:
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Height of cone and
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Height of slumped concrete
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👉 This difference is the slump value
Types of Slump
1️⃣ True Slump
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Concrete settles uniformly
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✔️ Acceptable and desired
2️⃣ Shear Slump
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One side slides off
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❌ Indicates lack of cohesion
3️⃣ Collapse Slump
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Concrete collapses completely
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❌ Indicates too much water
Recommended Slump Values (As per Practice)
| Type of Construction | Slump (mm) |
|---|---|
| Mass concrete | 25 – 50 |
| Footings | 25 – 75 |
| Beams & slabs | 75 – 100 |
| Pumped concrete | 100 – 150 |
Precautions During Slump Test
⚠️ Perform test immediately after sampling
⚠️ Use clean and calibrated equipment
⚠️ Do not disturb concrete after lifting cone
⚠️ Test should be done on a level surface
Advantages of Slump Test
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✔️ Simple and quick
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✔️ No laboratory required
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✔️ Suitable for site use
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✔️ Low cost
Limitations of Slump Test
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❌ Not suitable for very dry concrete
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❌ Not accurate for very high workability mixes
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❌ Does not measure strength
Site Engineer Tip 💡
If slump is too high, check:
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Excess water
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Over-dosage of admixture
If slump is too low, check:
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Improper mixing
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Low water content
Interview Questions (Quick Revision)
Q: What does slump test measure?
👉 Workability of concrete
Q: How many layers are used in slump test?
👉 4 layers
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