What is a Concrete Slump Test and Why is it Important?
Concrete is a fundamental building material that is necessary for a whole host of domestic and commercial projects. Regularly used in construction sites across the country, it’s essential that quality concrete mixes are selected to achieve the desired outcome.
Often, the consistency of a concrete mix will dictate whether or not it is suitable for the job at hand and will inform the type of concrete you purchase. However, even if you’ve selected a batch that fits the bill there may be times when one bag differs from the rest for whatever reason. In these cases the concrete may not be suitable, so it’s important to check this prior to use.
A concrete slump test is the best way to do this, and in this article, we’ll outline what a concrete slump test is and why it’s important.
What is a concrete slump test?
In basic terms, a concrete slump test is a test that ensures the concrete mix you intend to use meets the necessary standards for the job at hand.
The concrete slump test will measure the consistency of the mix, checking how easily it pours. This is important as a certain consistency is likely required for the construction project you’re working on.
Not only will a slump test check a mix’s consistency, but it will also highlight if there are any issues or discrepancies with the batch that may need to be rectified before it is used.
Furthermore, the ‘slump’ will also let you know if the water-cement ratio is too high or if a mix has a high level of workability.
Why do a concrete slump test?
As mentioned above, the primary reason to conduct a concrete slump test is to check the consistency of the concrete as well as to measure its strength and overall quality.
Sometimes, a project will require a higher workability or concrete that flows at a greater rate. This is known as a higher slump and doing the test will give you peace of mind that the batch you’re using is appropriate before you begin. It is harder to rectify the problem of incorrect concrete being used after it has been poured, so it’s always worth doing the slump test before you start to make sure everything is in order.
As well as this, it’s important to check the water content of the mix. Water invariably makes concrete weaker, so if strength and durability are key to your project then a slump test will help here, too.
How to do a concrete slump test?
The concrete slump test is fairly straightforward to conduct and involves using a slump cone, a steel rod and a measuring stick.
If you need to do a concrete slump test follow the six key steps below:
- First, place the slump cone on a flat horizontal surface. Stand on the footholds on either side of the cone to ensure it is planted firmly on the ground.
- Next, fill the cone with concrete in three layers and use the steel rod to compact the mix after each layer has been poured. Make sure this is done in an even and uniform manner repeating the process 25 times per layer.
- When the cone has been completely filled, remove any concrete that has been overflowing the top of it. Also, make sure the concrete has been filled right to the top of the cone. Be sure to also remove any concrete that has been spilt at the bottom of the cone.
- Now, lift up the cone in a slow and steady until the cone is clear of the concrete. Then, place the cone upside down on the surface next to the concrete.
- At this point, the concrete will begin to slump. To measure the slump, grab your steel rod and place it across the top of the upturned cone so it overhangs the concrete.
- Now you can measure the slump and get your result. Measure from the rod down to the top of where the slump lies. The level of slump is measured to the nearest 5mm.
Now you understand how to conduct the concrete slump test, you can read the result and decide if any changes need to be made.
Results of a concrete slump test
The concrete slump test result will fall into four categories. This concrete slump range is as follows:
This means that the concrete has completely retained its shape. This means that the mix you are using is extremely dry and it is a batch that is commonly used during road construction.
If the concrete has largely retained the shape of the cone, it indicates what is known as a true slump. This indicates that the mix is cohesive and the workability isn’t too high. This is the only reliable result when it comes to understanding the workability of the concrete you’re using.
For a shear slump, the top half of the concrete will subside significantly leaning obviously to one side. This means the mix has workability but the cohesion is very low. In these cases, the mix may have too much water and it will need to be amended.
One of the most obvious results, a collapse slump is exactly as it sounds. The mix will not retain any shape and will completely collapse, meaning that the water-cement ratio is far too high and the concrete is weak. This means the mix will need to be fully amended to make it usable.
Here at Concrete Supply UK, we’ve spent many years providing quality concrete mixes to domestic and commercial customers across the country. Every product we provide is formulated to the exact requirements of our customers, meaning you’ll always be provided with a bespoke mix that has been designed with your project in mind. This means you can rest assured that you will always receive a concrete mix of a high quality and most suitable consistency. For more information, get in touch with our team today.