What Is Concrete Slump? Significance And Testing Explained.

Concrete is the traditional water, cement, gravel, and sand mixture. Modern concrete mixes consist of other ingredients like plastics, fibers, and other chemical admixtures.

The mixture and ingredients proportion helps to identify the concrete properties, including slump. But what is concrete slump? Well, you can say that it is the measure of workability or concrete consistency.

Moreover, it measures how easy the concrete is to mold, push and smooth out. The slump rating shows the concrete suitability, purpose, and application. The higher the slump, the concrete becomes more workable.

Suppose the concrete slump is low, it will not give you shape quickly. And if it is too high, you may face the risk of having the sand, cement, and gravel settle out of the mixture, making it unusable.

So, how often did you try to find out or check out with your contractor about how they decide the quantity and quality of the concrete used? Did they check out stability and set parameters?

However, in most cases, the answer will be ‘No.’ It is why knowing about the concrete slump is necessary. Let us discuss the introduction of a concrete slump, its significance, and how to do the testing?

What Is Concrete Slump?

Reaching this point, you might be having the idea of a concrete slump. But getting into detailed introduction and definition –
‘The slump of concrete is the consistency of fresh concrete before setting, and so it is said that the higher the slump is, the more fluid concrete becomes. It is a bit confusing for a complex procedure, but is pretty simple when it boils down.’’

You will suppose that the term ‘slump’ is out of place in the concrete context that is referring to the act of sinking or slouching. But it is rather apt – it is called this because it is measurable by testing the pile of concrete slumps down when left for standing. All you need to do is fill the cone with the concrete sample, remove the cone and measure out how far concrete slumps.

Significance Of Concrete Slump Testing

Knowing and determining the concrete consistency will be helpful for various reasons. More importantly, it will allow you to preview your concrete before setting. Other than this, it will also allow you to make adjustments to the mix (if necessary) for creating a better product having more consistency.

Before spending resources manufacturing the entire batch of subpar concrete, you will have to give time and opportunity to remix and save money and time.

How To Do Slump Test Of Concrete?

To perform the slump test of concrete, first, you must take a slump cone called Abrams Cone and fill it with your newly mixed concrete. Then remove the cone, and you will see how much concrete slumped without any metal casing available.

Additionally, you can also observe results and measure how much concrete slumped by keeping the cone next to it. You can measure the difference between the height of the concrete slumped and the top of the cone.

Some Techniques Useful For ‘Concrete Slump’ Test

One of the crucial tests to check the concrete quality is the ‘concrete slump test.’ This test aims to establish the consistency of fresh concrete and find out the flow. It is also vital to measure the concrete workability and let you know the composition of the concrete mix. The main reason why this test is famous is its effectiveness and simplicity. The utilization of simple tools for performing the test is also one reason for its popularity. Apparatus used and steps to be followed are –

  • You can place a flat metal plate and if it is not available, go for the solid non-absorbent surface on the floor. The metallic cone-shaped tool can be placed on it with side handles to lift it.
  • Pour the Fresh concrete in three stages from the top. At every step, concrete is pressed down tightly around twenty-five times with the bullet-nosed metal rod that measures 2 feet.
  • Additional concrete is flushed from the top of the mold on the third and last phase.
  • Cone mold lifts upwards slowly without any disturbance to the concrete cone.
  • Concrete is then allowed to subside or fall.

How To check Result Of Concrete Slump Testing?

You can observe one of four outcomes as the result of the slump test –

True Slump

It is the slump outcome you are looking for, which means the concrete is at its optimum consistency. This result will observe that the mixture will essentially retain the shape once you remove the cone. You will see little slumping or flattening at its top.

Collapse Slump

If the entire shape collapses completely, the mixture is too watery and will require remixing.

Zero Slump

After Removing the cone, if you find the shape holds ultimately, your mixture is unworkable and too dry.

Shear Slump

The concrete mixture will slump down at one side dramatically, which indicates it has little cohesion or is too wet.

Class Of Concrete Slump With Its Use

The slump of concrete has categorization on the basis of class it falls into according to its average slump value and S1 to S5 range. Concrete in class S1 is a relatively dry mix, resulting in more fluid moving up the classes.

Class S1 Slump

This class has a slump range of 10 to 40, with 20 as the target slump. Class S1 concrete works excellent for pipework bedding and Kerb.

Class S2 Slump

Its slump range is 50 to 90 has 70 as the target slump. Class S2 concrete is helpful for hard-standing slabs and strip footings.

Class S3 Slump

This class S3 slump ranges from 100 to 150 having 130 as the target slump. S3 concrete class is helpful for trench-fill foundations that need high flow.

Class S4 Slump

This class S4 Slump range is about 160 to 210, having 180 as the target slump. It needs the help of an experienced concrete technologist because of their special uses like slabs, piling concrete, and foundations.

Class S5 Slump

Class S5 has the slump range 210 self-leveling having 220 as target slump that is useful the applications like piling, slabs, and foundations.


So you now have a clear idea about the concrete slump and its role in the construction sector. These are some steps to follow for testing concrete slumps and preparing concrete consistency according to your use.