Grain Size Distributions

A grain size distribution plot is a special purpose graph generally used to depict the results of a sieve analysis, commonly known as a "gradation test". The sieve analysis determines the gradation (the distribution of aggregate particles, by size, within a given sample) in order to determine compliance with design, production control requirements, and verification specifications.

Typically a grain size distribution plot shows grain sizes in millimeters on the X axis with a reversed (largest-to-smallest) logarithmic scale:

Grain Size Distribution Plot
US Standard Sieves

DPlot shows material classifications below the X axis, using either the AASHTO (American Association of State Highway and Transportation Officials) designations or the Udden-Wentworth scale:

AASHTO material designation		Udden-Wentworth scale
Size in millimeters	Size class	Size in millimeters	Size class
500	Cobbles	4096	Boulder
76.2	Coarse Gravel	256	Cobble
19.05	Fine Gravel	64	Pebble
4.75	Coarse Sand	4	Granule
2.0	Medium Sand	2.0	Very Coarse Sand
0.425	Fine Sand	1.0	Coarse Sand
0.075	Silt or Clay	0.5	Medium Sand
		0.25	Fine Sand
		0.125	Very Fine Sand
		0.0625	Coarse Silt
		0.031	Medium Silt
		0.0156	Fine Silt
		0.0078	Very Fine Silt
		0.0039	Clay

Sieve sizes are shown along the top of the graph using AASHTO-standard sizes as shown above, or British standard sieve sizes:

Grain Size Distribution Plot
British Standard Sieves

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Grain Size Distributions