02 Aug, 2023
Simtec Materials Testing Laboratory

At Simtec Materials Testing Ltd, our industry-leading team are experts in the field of concrete testing.

We have specialist and accurate technology available. This allows us to measure whether the workability is consistent between loads or batches of concrete in order to see if the measured slump is within the specified limits of the concrete specification. This will then give an idea if it is appropriate for use in roads, pavements, structures, or foundations.

What Is a Concrete Slump Test?

A concrete slump test is a method used to check multiple loads/batches of the same concrete for consistency and compliance with the required specification. Concrete slump tests also help to identify any workability issues in a mix allowing this to be rejected or corrected before it is used on-site. 

As concrete can be used in a variety of ways, it is important to ensure that the concrete mix is suitable for specific projects and that it meets BS EN standards for its intended use.

There are generally 8 key stages to carrying out a concrete slump test:

How to Perform a Concrete Slump Test

Step 1

The cone and baseplate should be cleaned thoroughly before every test the inside and outside. Use water and remove excess with a damp cloth on the inner surface to ensure that the concrete doesn’t stick to the cone or baseplate.

Care should be taken to ensure that there is no excess water on the surface of the cone and baseplate. Place the baseplate on even/flat ground and ensure that it is stable. Stand on the metal tabs either side of the slump cone to keep it firm on the baseplate.

Step 2

Sample the concrete mix for testing. You should ensure that the aggregate does not exceed 40mm to perform an accurate test.

It is important to carry out the test within 3 minutes of starting the slump test. 

Step 3

Use a scoop to fill one-third of the cone with concrete and compact the concrete using a tamping rod by aligning the rod with the slop of the cone. We recommend using a slump rod 600mm length with a 16mm diameter with rounded ends.

Using the tamping rod tamp the concrete 25 times around the entire cross-section of the concrete in the cone. It is important to take care with this step to ensure that you do not hit the base plate with the tamping rod. 

Step 4

Fill the cone with two-thirds of the same sample concrete mix and repeat step 3 whilst ensuring that the tamping rod penetrates just penetrates the previous layer.

Step 5

Again, using the same sample batch of concrete, fill the cone to slightly overflowing and compact the last layer with the tamping rod, ensuring 25 strokes and just penetrating the second layer. It is important that you do not go straight through the second layer.

Step 6

Remove any excess concrete from the top of the concrete slump testing cone, you can use the tamping rod to do this. Clean any excess concrete from the outside of the cone and what has spilled onto the metal plate.

Once the cone is clean, lift off the cone taking between 2 and 5 seconds. Remove the cone as close to vertical as possible. It is important to ensure this is taken off carefully to get an accurate reading. If you take the cone off at an angle this could provide you with a false reading. 

Step 7

The concrete will then slump or subside. Using a steel slump rod place this on top of the removed cone, pointing over the pile of concrete.

You should then be able to see how high the pile is in comparison to the cone. 

Step 8

Measure the slump by recording how far the top of the concrete is from the rod on top of the slump cone. You should be able to clearly observe the shape of the concrete also. 

We recommend taking measurements to the nearest 5mm.

Concrete Slump Test Results

If you have carried out these 8 key steps, then you should receive one of the following results:

  • Zero Slump 

The mix has not moved at all and has maintained its shape. This means the mix is very dry and not suitable for use construction. 

  • True Slump 

The concrete sinks slightly but maintains its shape. This result means that the mix sticks well together and isn’t too wet. 

  • Shear Slump 

Concrete leans to one side and the top has sunk. This means that the mix is far too wet, and the mix is not sticking together. The ratio of cement and water would need to be re-addressed or a different test method used to see the workability of the concrete.      

  • Collapse Slump 

If the concrete cone collapses completely within itself, then the water ratio is far too high, and the mix would need complete readjusting.

Limitations of a Concrete Slump Test

Concrete slump testing is not suitable for concrete formed of aggregate higher than 40mm.

It is only suitable for slumps between 10 to 220mm.

On-Site Concrete Slump Testing UK

Simtec Materials Ltd was established in 2007 and built on a foundation of many years of experience in the construction and civil engineering industry.

Our team of experts provide comprehensive on-site testing across the UK including:

  • CBR, Plate Load and Diamond Core Drilling
  • On-Site Material Testing e.g. Concrete Slump Testing 
  • Lab Testing 
  • Routine Quarry and Plant Outputs

We strive to always deliver a premium onsite service for all our customers to ensure that their projects can continue safely with accurate information and without unnecessary delays.