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 a concrete slump?
Concrete slump is a measure of the consistency or workability of fresh concrete. It is determined by measuring the depth and the relative angle at which the freshly mixed concrete settles after it has been filled into a mold.
The result reflects how easy it is to move, handle, place, and compact the concrete mix in its intended location.
The slump rating shows the concrete suitability, purpose, and application. The higher the slump, the concrete becomes more workable.
For instance, if the slump is low, it will not give you the same amount of plasticity or workability that a higher slump will provide. If it’s too high, you may face the risk of having sand, cement, and gravel settle out of the mixture, making it fairly 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?
Unfortunately, in most cases, the answer is no. That’s 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 let’s get into the details to understand it better.
‘The slump of concrete is the consistency of fresh concrete before it sets. It is said that the higher the slump is, the more fluid concrete becomes.
Some people may find it confusing, as the procedure itself is complex. However, when handled properly, the slump test can be very useful in determining the correct mix of concrete for a particular job.’
Some people might think that the term ‘slump’ is out of place in the concrete context. However, it is a useful measure for engineers and construction workers to assess the performance of concrete in various applications.
It is called the slump because it is measurable by testing the pile of concrete that slumps down in the mold. All you need to do is fill the cone with the concrete sample, remove the cone and measure out how far the concrete slumps.
Significance Of Concrete Slump Testing
Knowing and determining the concrete consistency is helpful for various reasons. For instance, this gives you the opportunity to preview your concrete before setting.
Aside from this, this also allows you to make adjustments to the mix (whenever necessary), to create a better product that has better consistency.
Before spending a huge ton of resources on a concrete project, it is very important to know the right mix of ingredients that will give you the desired result. With this test, you can get an idea about the quality of your concrete before starting on your project.
This means that concrete slump testing can help you save a significant amount of time and money at the same time.
How Does Concrete Slump Testing Work?
An Abrams Cone or slump cone is used to perform a slump test. This is usually a metal or plastic cone that has an adjustable handle that can be opened or closed. The goal of the test is to get the right amount of concrete into the cone without any air bubbles and then measure how far it slumps.
Fill it with your newly mixed concrete, then remove the cone. From there, you’ll see how much concrete has slumped with the absence of the metal casing.
Additionally, you may also perform more tests and observe how the concrete behaves before you start on your project.
You have the option to keep the Abrams cone side by side with the concrete and measure the difference between the two. This way, you’ll get a better understanding of the slump rate that your concrete has.
Some Techniques Useful For the ‘Concrete Slump’ Test
One of the crucial tests to check concrete’s 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. The apparatus used and the steps to be followed are:
- Place a flat metal plate. If it is not available, go for a solid non-absorbent surface on the floor. The metallic cone-shaped tool can be placed on it, using the side handles to lift it.
- Pour the fresh concrete in three stages from the top. At every step, press the concrete 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 in the third and last phases.
- Lift the cone mold slowly and carefully.
- From there, perform the test and let the concrete subside or fall.
How To Check the 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.
Classes of Concrete Slumps and Their Uses
The slump of concrete has a categorization, evaluated by the amount of slump and can be used for different purposes. Its class values will fall anywhere within the S1 to S5 range.
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 its special uses like slabs, piling concrete, and foundations.
Class S5 Slump
Class S5 has a slump range of 210 self-leveling having 220 as the target slump that is useful the applications like piling, slabs, and foundations.
Final Thoughts
The concrete slump is a measurement used to determine how well a concrete mixture works. This is by far one of the most important factors to take into consideration in terms of construction projects.
A higher slump concrete mixture may indicate a higher strength, while a lower slump is indicative of a less durable and weaker material.
It may also indicate more water in the mixture, which could lead to cracking or other forms of deterioration. Additionally, a slump can indicate how well the concrete will fill a form and whether it will have adequate compaction.
