What is Concrete Slump: Everything You Need To Know

How often did you try to find or check with your contractor that how do they decide the quality and quantity of concrete to be used and its stability be checked against any set parameters? Well, in most of the cases the answer will be a big NO! That’s perhaps why knowing what is concrete slump is important.


Concrete is widely used in building and construction of buildings, road, and repair works and in other works of the foundation. We all tend to ignore once we provide the contractor a specific quality or standard of constitute. It will all depend on him to decide the mix and strength of the concrete without understanding the need of the type of concrete to be used in the project.

Why Is Concrete Quality Important?

To understand, why you need to check the quality of concrete, you must first understand what concrete is. Concrete is a composite material consisting of coarse aggregate which is stick together with fluid cement. Most of the times, the concrete used is lime-based and is termed as the Portland cement concrete.

When a course is mixed with Portland cement and water, it produces a slurry which can be easily poured and molded into required shapes. As soon as the mixture becomes dry, it hardens and gives strength to the structure. The standard of the mixture should be appropriate to provide the following to the structure:

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    Check the quality, it should be uniform throughout the construction, so that equal strength is provided all across.
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    Examine that the strength of concrete is appropriate for the needs of the project and is suitable for stripping, stressing, and opening to traffic.
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    The concrete takes the required shape and the workability is as per the set standards.

Technique Used For the “Concrete Slump” Test

One of the critical tests to analyze the quality of concrete is the “Concrete Slump Test”. This test is conducted to establish the consistency of fresh concrete and to find out its flow. It is also critical in measuring the workability of the concrete and lets you know the composition of the mix.

The reasons why this test is preferred is its simplicity and effectiveness. The use of simple tools to perform the test is also a reason for its popularity. Steps and apparatus used are as follows:

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    A flat metal plate is placed; if not available then a solid, non-absorbent surface can be used, on the floor. A metallic cone shaped tool is placed on it with the dimensions- 100mm internal diameter on the top; 200mm internal diameter on the bottom and a height of 305mm. The cone has side handles to lift it.
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    Freshly prepared concrete is poured in three stages from the top. At each stage, the concrete is pressed down tightly twenty-five times with a bullet-nosed metal rod measuring 2ft.
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    On the third and the last stage, the extra concrete is flushed from the top of the mold.
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    The cone mold is slowly raised upwards without disturbing the concrete cone.
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    The concrete is then allowed to fall or subside by itself.

Review Of The Subsided Concrete

The manner or pattern in which the concrete sags is measured and observed and based on it the results are derived. Following are the possible ways and their interpretations:

  • Collapse
  • Shear
  • True Slump

If the cone just subsides and do not lose the shape, it is termed as True Slump. These are usually of low workability of 10-40mm and are used in foundation work with little reinforcements.

If at all the workability is found to be between 0-25mm, then the concrete is best suited for road construction. And in such cases, the worth of the test cannot be determined and is not taken as valid. You may say that this is the limitation of the test.


These are all about what is concrete slump. We hope that the above article would have helped you in understanding the basics of concrete slump. That said, do let us have your views and experiences. Got any query? Shout out in the comments below.

Abigail Jones

Hi, I'm Abigail. I like spending time tearing my house apart and putting it together back again. Join me on home improvement tutorials, tips on my blog.

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