Creating the right consistency of concrete is vital for the success of a project. Too wet, and it’s liable to crack and scale. Too dry, and it will be difficult to pour and handle. 

But how do you know if your concrete is at the ‘Goldilocks’ consistency? The best time to check is before it sets and the recommended technique is the concrete slump test. In this article, we take you through the benefits of a concrete slump test and outline how you can perform one accurately at your site. 

What is concrete slump? 

Simply put, concrete slump refers to the workability and/or consistency of the concrete mix. Slump can also be described as how fluid the concrete mix is. If it has a higher slump rating, it is more fluid and ‘workable’, and conversely, a lower slump rating means the mix is less fluid and workable. The slump of the concrete mixture is established using a slump test. 

Why do a concrete slump test? 

Understanding the consistency of your concrete mix is useful for several reasons. Essentially, it allows you to preview what your concrete will be like before it sets, allowing you to make adjustments to the mix to create a better product with more favourable consistency. In effect, before you spend resources producing a whole batch of subpar concrete, you give yourself time and opportunity to remix – saving time and money. 

How to do a concrete slump test 

To perform a concrete slump test, first take a slump cone, also known as an Abrams cone, and fill it with your newly-mixed concrete. The cone will then be removed and the concrete will be observed in relation to how much it ‘slumps’ without the metal casing around it. You can both observe the result and also take a measurement of how much the concrete has slumped by placing the cone next to it and measuring the difference between the top of the cone and the height of the slumped concrete. 

There are four outcomes of the slump test: 

  • Zero slump: If the shape completely holds once the cone is removed, the mixture is too dry and unworkable. 
  • True slump: This is the slump result you are aiming for, and means the concrete is at optimum consistency. The mixture will largely retain its shape once the cone is removed, save for a little slumping or flattening at the top. 
  • Shear slump: The mixture will slump dramatically down one side, and this means it is too wet or has little cohesion. 
  • Collapse slump: If the shape completely collapses, the mixture is far too watery and will need remixing. 

Classes of concrete slump 

As well as observation, measurements of the difference between the height of the cone and the height of slumped concrete should also be taken. This way, you can classify the slump according to European standards (BS 8500). 

Class  Range (mm) Target slump (mm)
S1 10 – 40  20
S2 50 – 90  70
S3 100 – 150 130
S4 160 – 210 180
S5 210 + 220


Each of the five classes outlines a target slump value, and each class has uses for different applications depending on the consistency. In some cases, if a certain class of slump hasn’t been achieved for the application you’re using it for, it may require remixing. In any event, an expert concrete supplier will be able to give advice. 

For professional concrete supply in the Hertfordshire area and beyond, look no further than EasyMix Concrete. Our experts know what makes the perfect concrete mix for your specific needs, and can offer both ready mixed and on-site options. For a truly convenient service, we have same- and next-day delivery options, so get in touch to discuss your project with our specialists.