PSD (Particle Size Distribution) Testing: Know Your Material Grading with Confidence
Particle Size Distribution (PSD) testing—also known as grading or sieve analysis—is a fundamental test used to determine the proportions of gravel, sand, silt, and clay in a material. It is a key part of soil and aggregate characterisation and provides essential data for design, specification, and compliance.
To measure the finest fractions accurately, sedimentation testing (typically by hydrometer or pipette) is used alongside sieving. This allows reliable calculation of silt and clay particles smaller than 63 µm, giving a full grading profile.
Why PSD testing matters
PSD results help engineers and project teams make informed decisions about:
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whether a material is well graded or gap graded
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uniformity coefficient and likely material behaviour
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estimated permeability and erodibility
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suitability as construction fill material (including classification against project/specification requirements such as SHW Series 600/800)
PSD testing is also important for topsoil and subsoil classification, supporting soil texture assessment and helping confirm the right balance of sand, silt, clay, and gravel for intended use.
Why choose The Testing Lab PLC?
At The Testing Lab PLC, we provide accurate PSD testing with clear, practical reporting that helps you make fast, confident decisions. Whether for earthworks, fill classification, topsoil, or subsoil assessment, we deliver dependable results and responsive support.
Need PSD / grading analysis? Contact The Testing Lab PLC to discuss your samples and turnaround requirements.
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Your analyst, Lee, was very helpful and his suggestions and advice appreciated.
We would have no hesitation in recommending The Testing Lab and will be in touch soon with regards arrangements for a full asbestos survey for the rest of the site.
TTL have been working directly as my analyst for the last 12 months on a very complex asbestos removal scheme, they have achieved all of their KPI’s without fail and on a number of occasions surpassed their SLA in acting for us on planning issues associated with the demolition in regard to contamination which cannot be removed as part of the normal sequence of operation.
There reports are always issued within timescales and they have policed the reports by the Licensed asbestos contractor faultlessly sometimes in very difficult circumstances.
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