Sieve Analysis of Aggregate: Steps and Gradation Curve

A sieve analysis of aggregate shows how much of a sand, gravel or crushed stone sample falls into each particle size. It is the test behind every stone size name, from #57 to dense grade base to concrete sand, and the reason two "3/4 inch" stones from different quarries can pack and drain completely differently. This guide covers the sieve sizes, how the test is run, how to calculate percent passing and fineness modulus, and how to read a gradation curve, with a worked example.

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The standards and the sieves

In the US, the dry sieve analysis follows ASTM C136 or AASHTO T 27. When the amount of fine dust and clay matters, the sample is first washed over the No. 200 sieve following ASTM C117 or AASHTO T 11. Sieves are stacked with the largest openings on top. Common sizes include:

Coarse sieves named by opening: 2 inch, 1 1/2 inch, 1 inch, 3/4 inch, 1/2 inch and 3/8 inch.
No. 4 (4.75 mm), the usual dividing line between coarse and fine aggregate.
No. 8 (2.36 mm), No. 16 (1.18 mm), No. 30 (0.60 mm), No. 50 (0.30 mm) and No. 100 (0.15 mm).
No. 200 (0.075 mm). Anything passing it is called fines, the silt- and clay-sized dust.

How a sieve analysis is run

Get a representative sample. Material is taken from the stockpile or belt and reduced with a sample splitter or by quartering so the test portion matches the whole.
Size the sample. ASTM C136 sets minimum masses by nominal maximum size. Coarse aggregate needs more as stone gets bigger, for example about 1 kg for 3/8 inch material, 5 kg for 3/4 inch and 10 kg for 1 inch. Fine aggregate needs at least 300 g after drying.
Dry to constant mass and weigh.
Wash if required, dry again and weigh to find the loss through the No. 200 sieve.
Sieve. The stack is shaken by hand or in a mechanical shaker until hardly any more material passes. Sieves must not be overloaded, or fine particles cannot reach the openings.
Weigh each sieve's contents and the pan.
Check the total. The retained masses should add up very close to the starting mass. C136 treats a difference of more than 0.3 percent as a reason not to use the result for acceptance.

How to calculate percent passing

Cumulative retained on a sieve = mass on that sieve + mass on every larger sieve.
Cumulative percent retained = cumulative retained ÷ total mass × 100.
Percent passing = 100 − cumulative percent retained.

Worked example: a sand sample

Here is a made-up 500 g sand sample, dry sieved, used only to show the math. The masses retained added up to 499 g, a 0.2 percent difference from the starting mass, so the result is usable.

3/8 inch: 0 g retained, 100 percent passing
No. 4: 15 g, cumulative 15 g, 3.0 percent retained, 97.0 percent passing
No. 8: 60 g, cumulative 75 g, 15.0 percent retained, 85.0 percent passing
No. 16: 85 g, cumulative 160 g, 32.1 percent retained, 67.9 percent passing
No. 30: 110 g, cumulative 270 g, 54.1 percent retained, 45.9 percent passing
No. 50: 120 g, cumulative 390 g, 78.2 percent retained, 21.8 percent passing
No. 100: 75 g, cumulative 465 g, 93.2 percent retained, 6.8 percent passing
No. 200: 25 g, cumulative 490 g, 98.2 percent retained, 1.8 percent passing
Pan: 9 g

Fineness modulus

Fineness modulus (FM) boils a sand's gradation down to one number. Add the cumulative percent retained on the standard sieves (No. 100, 50, 30, 16, 8, 4, 3/8 inch and up) and divide by 100. The No. 200 is not included.

For the example: (3.0 + 15.0 + 32.1 + 54.1 + 78.2 + 93.2) ÷ 100 = 2.76. ASTM C33 calls for fine aggregate for concrete to fall roughly between 2.3 and 3.1, so this sand sits in the normal range. A higher FM means a coarser sand. Our mason sand vs concrete sand guide shows why the two sands behave differently.

Reading the gradation curve

Plot percent passing against sieve size on a log scale and the shape tells the story.

Well graded (dense graded): a smooth S-curve across many sizes. Small pieces fill gaps between big ones, so it packs tight. Road base and dense grade aggregate are built this way.
Uniform or open graded: a steep curve over a narrow size range. It drains freely but does not lock up on its own. #57 stone is a classic example.
Gap graded: a flat step where some middle sizes are missing.

Engineers also read off D10, D30 and D60, the sizes that 10, 30 and 60 percent of the sample pass. The coefficient of uniformity is D60 ÷ D10, and the coefficient of curvature is D30² ÷ (D10 × D60). Under the Unified Soil Classification System, a gravel counts as well graded when the first is at least 4 and the second is between 1 and 3; for sand the first must be at least 6.

Why gradation matters on the job

Stone specs are gradation bands. A load fails if too much falls outside the allowed percent passing.
Asphalt mixes are designed around a target gradation; see what a JMF is in asphalt.
Drainage depends on fines. A few extra percent passing the No. 200 can turn a free-draining stone into one that holds water, which is the point of washed vs unwashed gravel.
Weight per yard shifts too. Well-graded blends usually weigh more per cubic yard than one-size stone, which affects tonnage. The crushed stone calculator lets you adjust density.

Questions people ask

What is a sieve analysis of aggregate?

It is a test that shakes a dried sample of sand, gravel or crushed stone through a stack of sieves with smaller and smaller openings, weighs what stays on each one and reports the percentage of the sample passing each size. The result is the aggregate's gradation.

Which standard covers sieve analysis of aggregate?

In the US, ASTM C136 and AASHTO T 27 cover the sieve analysis. ASTM C117 and AASHTO T 11 cover washing the sample to measure material finer than the No. 200 sieve.

How do you calculate percent passing?

Add the mass retained on each sieve and every larger sieve to get cumulative retained, divide by the total sample mass and multiply by 100 for cumulative percent retained. Percent passing is 100 minus that number.

What is fineness modulus?

Fineness modulus is the sum of the cumulative percentages retained on a standard set of sieves, divided by 100. ASTM C33 calls for fine aggregate for concrete to fall roughly between 2.3 and 3.1. Higher numbers mean coarser sand.

How big should a sieve analysis sample be?

ASTM C136 sets minimums by nominal maximum size. Coarse aggregate needs more mass as stone gets larger, for example about 1 kg for 3/8 inch stone and about 5 kg for 3/4 inch. Fine aggregate needs at least 300 g after drying.

What does well graded mean?

A well-graded aggregate has a smooth spread of sizes from coarse to fine, so smaller pieces fill gaps between larger ones and the material packs densely. Uniform or open-graded material is mostly one size, and gap-graded material skips some sizes.

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