Particle Size Distribution

Particle size distribution is commonly known as PSD or Grading and is the most common test for aggregates in the construction industry. The test is used to determine size fractions in accordance with BS EN 933-1. The main reason for the test is to make sure the many materials available are compliant with the size fractions and suitable for use in many different applications throughout the industry.

Our trained technicians will visit your site and sample the materials under British Standards 932 series. We can sample your materials from a bay, quarry stockpile or a conveyor. The samples will then be individually marked and delivered to our materials test facility ready for testing.

Materials below 32mm will take 3 working days to complete with an additional 12 - 24 hours for verification and reporting.

Sample types we commonly grade

  • sand
  • ballast including railway/track ballast
  • recycled sand
  • recycled gravel
  • limestone fines
  • limestone
  • gravel
  • granite fines
  • granite
  • glass sand
  • fines

The price we give you is the price of everything all in, it's that simple. We don't have hidden charges or costs for mobilization, reporting, disposal or anything else for that matter. Talking about disposal, we do it all responsibly and in-line with current and environmental legislation.

The PSD grading process

The Omega Group has adopted the wet "washing and sieving" method to give the most accurate results. A PSD test can be completed dry, however, very inaccurate and does not allow complete separation of fines.

The test consists of sample collection and reduction. Once the aggregate sample is reduced it is washed and then oven dried for a minimum of 16 hours. Once the constant mass has been achieved and the sample is dry then the strict grading process begins. The material is sieved using different size fraction sieves as set out by varying standards and client specification.

Different sizes of material and aggregate types take different amounts of time to be tested due to them having to be oven dried. Recycled materials usually take longer to dry due to the fact they must be dried at a lower temperature due to the potential presence of bitumen.

CE marking and use in concrete

It is now a requirement to have any material that goes into concrete production to be C.E. Marked and one of those tests is Particle Size Distribution. This is paramount to ensure the materials you supply or use are to the standard.

Can we send our material samples directly to you?

Yes, you can. If you have sampled your own materials, you can arrange for them to be delivered to us or we can arrange for Nationwide collection, all at very competitive prices.


Our unique test reports tell you everything you need to know and furthermore, whether the test has passed or failed. All material test reports are analysed Manager or Director prior to issue. All test reports will also be available on our secure client portal.

This article forms part of our material services.