What is slump test? and what is the Purpose for it? | Q & A

What Is Slump Test?

The slump test is a field test conducted on fresh concrete to measure its workability and consistency—that is, how easily the concrete can be mixed, transported, placed, and compacted.

It is the most common on-site test for fresh concrete.

Purpose of Slump Test

The slump test is performed to:

1. Check workability of concrete before placing

2. Maintain uniformity between different batches

3. Detect:

   • Excess water

   • Improper mix

4. Ensure concrete is suitable for:

   • Pumping

   • Concreting in congested reinforcement

Slump Test Procedure (Brief)

1. Place slump cone on a level, non-absorbent surface

2. Fill cone with concrete in 3 layers

3. Each layer tamped 25 times

4. Lift the cone vertically

5. Measure the drop in height (slump) in mm

Types of Slump (Interview Point)

• True slump – Uniform subsidence (acceptable)

• Shear slump – Mix lacks cohesion

• Collapse slump – Excess water, poor mix

Typical Slump Values (Guide)

Work Type            Slump (mm)

One-Line Interview Answer (Perfect)

Slump test is a field test used to measure the workability and consistency of fresh concrete to ensure it is suitable for placing and compaction.

Common Interview Follow-Up

Q: What does high slump indicate?
A: High workability or excess water.

Q: What does low slump indicate?
A: Stiff mix, difficult compaction.

Site Tip for Fresh Engineers

• Always do slump test before pouring concrete

• Never add water to concrete after slump test without approval