Aggregate grading—the proportional distribution of particle sizes in sand, gravel, or crushed stone—is measured using British Standard BS EN 933-1:1997, which provides the reference method for determining particle size distribution through sieve analysis. This standard applies to natural and artificial aggregates up to 90 mm nominal size.
BS EN 933-1 specifies a standardised sieving procedure. A representative test sample is passed through a nested stack of sieves with progressively finer mesh apertures. Retained material on each sieve is weighed, and cumulative percentages passing each aperture are calculated and plotted.
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The resulting grading curve shows whether the aggregate is uniformly graded, gap-graded, or continuously graded. For concrete and mortar producers, understanding aggregate grading helps predict mix behaviour and optimise material selection.
The standard superseded BS 812-103.1:1985 and has since been updated by BS EN 933-1:2012, though the 1997 version remains widely referenced in older specifications and contracts.
For site engineers, specifiers, and batching plant operators, regular sieve analysis of delivered aggregate is important to monitor consistency. Changes in quarry extraction or stockpile blending can affect grading, which in turn influences concrete performance and specification compliance.
