A sieve analysis is one of the clearest ways to understand an aggregate product.
The pile may look like clean stone, road base, pea gravel, concrete sand, or crusher run. The sieve analysis shows what is actually in it. It tells you how much of the material is coarse, how much is fine, whether the product is narrowly graded or well graded, and whether it is likely to drain, compact, or meet a specification.
For contractors, producers, engineers, and buyers, this matters because aggregate performance is not controlled by the product name alone. Names vary by region. A sieve analysis gives the common language.
This guide explains what a sieve analysis is, how to read percent passing and percent retained, why gradation curves are usually plotted on a semi-log chart, and what the results mean for drainage, base rock, concrete aggregate, sand, and aggregate blending.
What A Sieve Analysis Measures
Aggregate is made of particles of many sizes. Some particles may be several inches across. Others may be sand-sized. Others may be dust, silt, or clay-sized material that is difficult to see individually.
In theory, you could measure every particle. In practice, that would be slow, inconsistent, and almost impossible for small or irregularly shaped pieces. A sieve analysis solves the problem by passing a representative sample through a stack of sieves.
Each sieve has openings of a known size. If a particle passes through a sieve, it is smaller than that opening. If it stays on the sieve, it is larger than that opening.
The test does not measure a perfect particle diameter. Real rock particles are not spheres. They can be flat, elongated, angular, rounded, rough, or flaky. But a sieve analysis gives a practical size distribution that the aggregate industry can measure, compare, and specify.
The Basic Test Setup
A typical sieve analysis uses a nested stack of sieves arranged from largest opening on top to smallest opening near the bottom. A pan sits below the smallest sieve to catch the finest material.
The sample is dried unless the method requires washing for fine material. The sample is then shaken by hand or in a mechanical sieve shaker. Coarse material remains on the upper sieves. Finer material passes lower through the stack.
After shaking, the material retained on each sieve is weighed. The lab then calculates percentages based on the original sample weight.
For coarse aggregate, larger rectangular sieves or screens may be used. For fine aggregate, standard round sieves are common. The exact sample size, washing procedure, sieve stack, and calculation method should follow the applicable test method or project requirement.
For many construction aggregate applications, common references include AASHTO T 27 and ASTM C136 for sieve analysis, and AASHTO T 11 or ASTM C117 when accurately measuring very fine material passing the No. 200 sieve. Project specifications may call out specific methods.
Why Representative Sampling Matters
A sieve analysis is only as good as the sample.
If a loader takes material from the coarse outer edge of a stockpile, the test may look coarser than the actual product average. If the sample comes from a fine pocket, the test may look finer. If a stockpile is segregated, one small sample may not represent the entire pile.
Representative sampling usually means taking increments from the right locations, combining them, reducing the sample properly, and avoiding contamination or loss of fines. For job-critical work, sampling procedures are not a formality. They are part of the test.
This is one reason aggregate producers care about stockpile handling. A well-screened product can still test inconsistently if it segregates during stacking, reclaiming, or loading.
Percent Retained
Percent retained tells you how much of the total sample stayed on a specific sieve.
For example, if a 1,000-pound test sample leaves 120 pounds on the No. 4 sieve, then 12 percent is retained on the No. 4 sieve.
Percent retained is useful because it describes the material sitting in a size interval. If material is retained on the No. 4 sieve, it passed the sieve above it but did not pass the No. 4. That means it belongs roughly in that size range.
Percent retained is often helpful when thinking about how much material falls between adjacent sieves. It can reveal whether a product has most of its mass in one narrow range or is spread across many sizes.
Cumulative Percent Retained
Cumulative percent retained adds the material retained on a sieve plus all coarser sieves above it.
For example, if 5 percent is retained on the 3/8-inch sieve and 20 percent is retained on the No. 4 sieve, then the cumulative retained at No. 4 is 25 percent.
Cumulative retained is useful because it tells you how much of the sample is larger than a given sieve opening.
Some charts and calculators use percent passing. Others use cumulative retained. They are related:
Percent passing = 100 - cumulative percent retained.
If the cumulative retained at a sieve is 25 percent, then 75 percent is passing that sieve.
Percent Passing
Percent passing is the most common way to read aggregate specifications and gradation charts.
Percent passing tells you how much of the total sample is smaller than a given sieve opening. If 75 percent is passing the No. 4 sieve, then 75 percent of the sample is smaller than the No. 4 opening and 25 percent is retained on the No. 4 or larger sieves.
Specifications are often written as percent passing ranges. A product might be required to have percent passing within a lower and upper limit at several sieve sizes. To pass the specification, the tested material must normally fit the required band at each listed sieve.
That last part is important. Meeting one sieve does not mean the whole product meets spec. A material can hit the target at the No. 4 sieve and still be too fine at No. 200 or too coarse at a larger sieve.
Percent Passing Versus Percent Retained
Percent passing and cumulative retained describe the same test from opposite directions.
Percent passing asks: how much is smaller than this sieve?
Cumulative retained asks: how much is larger than this sieve?
Percent retained on a single sieve asks: how much is in this approximate size interval?
This difference matters when reading charts. In a percent passing view, the curve usually starts near 100 percent at the largest sieve and moves downward toward smaller sieve sizes. In a cumulative retained view, the curve starts near zero at the largest sieve and climbs as sieve sizes get smaller.
If you are comparing two charts, make sure they use the same view. A line that looks "high" on a percent passing chart means more fine material passing that sieve. A line that looks high on a cumulative retained chart means more material retained at or above that sieve.
Why Gradation Curves Use A Semi-Log Scale
Sieve openings cover a large size range. A chart might include 3-inch rock, 1-inch rock, a No. 4 sieve, a No. 30 sieve, a No. 100 sieve, and a No. 200 sieve. Those openings are not evenly spaced in ordinary inches.
To show large and small sizes on the same chart, gradation curves are usually plotted with sieve opening size on a logarithmic x-axis and percent passing on a linear y-axis.
That is why a gradation chart may look unfamiliar at first. The spacing between sieve labels is not just visual decoration. It reflects the large differences in opening size.
This semi-log view is useful because it shows the shape of the gradation. A very steep curve means many particles are concentrated around a narrow size range. A flatter curve means the material contains a broader range of sizes.
Uniform, Open-Graded, Well-Graded, And Gap-Graded
Gradation words describe the shape of the size distribution.
A uniformly graded material has most of its particles in a narrow range. Clean chip stone and some decorative products can behave this way. Uniform materials often have more open voids because there are not enough smaller particles to fill the spaces between the larger particles.
An open-graded material has limited fines and a structure with connected voids. This can be useful for drainage, but it may not compact into a tight surface.
A well-graded material contains a broad range of particle sizes. Smaller particles fill the spaces between larger particles. Many base products are designed this way because well-graded aggregate can compact into a dense mass.
A gap-graded material is missing much of one intermediate size range. It may have coarse and fine particles but fewer middle sizes. Gap grading can be intentional in some engineered mixtures, but in ordinary aggregate supply it can also indicate a blend or process issue that needs attention.
The gradation curve helps reveal which type of material you are looking at.
What The No. 4 Sieve Often Means
The No. 4 sieve is a common dividing point between coarse and fine aggregate in many construction discussions. Material retained on the No. 4 is generally treated as coarse aggregate. Material passing the No. 4 is generally in the fine aggregate range.
That does not mean the No. 4 is the only important sieve. It just appears often because it is a practical boundary between gravel-sized particles and sand-sized particles.
For base materials, the No. 4 can show how much sand-sized material is available to fill voids. For concrete and asphalt aggregate, it may help distinguish coarse and fine fractions. For blending, it can act as one of several control sieves.
What The No. 200 Sieve Means
The No. 200 sieve is one of the most important fine sieves in aggregate work. Material passing the No. 200 is very fine. It can include rock dust, silt, and clay-sized particles.
This material affects performance out of proportion to its size. A small percentage of plastic clay fines can hold water, coat larger particles, and reduce strength or bonding. Clean mineral dust may behave differently from clay. That is why some specifications care not only about how much passes No. 200 but also about plasticity or other fines quality indicators.
For drainage stone, too much No. 200 material can clog voids. For compacted base, some fines may help packing, but excessive or plastic fines can make the layer water-sensitive. For concrete sand, very fine material can influence water demand and workability. For asphalt, fines affect the aggregate structure and binder interaction.
The No. 200 value is not automatically good or bad. It has to be interpreted for the product and use.
Washed Sieve Analysis
Fine dust can cling to larger particles. If a dry sieve analysis is used by itself, the test may understate the amount of very fine material because some fines stay stuck to coarser particles.
A washed sieve analysis helps measure fine material more accurately. The sample is washed over a fine sieve, commonly the No. 200, so dust, silt, and clay-sized particles are separated and measured.
This matters for products where fines control performance. If a drainage product is supposed to be clean, washing the sample helps reveal whether fine particles are actually present. If concrete sand is being evaluated, washing can help determine whether material passing No. 200 is within the allowed range.
Reading A Gradation Table
A gradation table usually has sieve sizes in one column and percent passing in another. A specification table may also include lower and upper limits.
Start with the largest sieve. Most products should show 100 percent passing at some top sieve. That sieve gives a sense of maximum particle size.
Then move down the table. Watch how fast percent passing drops. A sharp drop over one or two sieves means the product is concentrated in a narrow size range. A gradual drop means the product contains a wider range of sizes.
Finally, look at the smallest sieves. The No. 100 and No. 200 values tell you about dust and very fine material. For clean stone, those values should usually be low. For dense base, some fine material is expected. For sand, those sieves help show how fine the sand really is.
If there are spec limits, compare every listed sieve. A product can be too coarse at one sieve and too fine at another.
Reading A Gradation Chart
On a percent passing chart, the y-axis shows percent passing from 0 to 100. The x-axis shows sieve opening size, usually largest on the left and smallest on the right, depending on the chart style.
A product curve inside a specification band is generally within the gradation limits at the plotted sieves. A curve above the band means too much material is passing that sieve, so the product is too fine at that point. A curve below the band means too little material is passing, so the product is too coarse at that point.
The shape matters too. A smooth curve often indicates a continuous range of particle sizes. A curve with a flat step or sudden jump may indicate a missing size range or a gap-graded material.
When comparing two materials, look at both the curve and the application. The "better" curve depends on whether you need drainage, compaction, concrete workability, asphalt performance, or blending into another product.
Example: Clean Stone
A clean stone product usually has a relatively narrow gradation and low fines. On a percent passing chart, the curve may drop sharply between the sieve that the stone mostly passes and the sieve that mostly retains it.
This kind of product can have good void space. That makes it useful for many drainage or decorative applications. But the same open void structure can make it less stable as a final driving surface because the particles do not have enough smaller material to lock them together.
If you see a clean stone with unexpectedly high percent passing at the No. 200, that may indicate dust, clay, contamination, stockpile issues, or a product that is not as clean as expected.
Example: Dense Base Or Crusher Run
A dense base product should normally show a broader range of particle sizes. It may have coarse particles for structure, sand-sized particles to fill voids, and controlled fines to help compaction.
On the gradation chart, the curve is usually less steep than a clean stone. It moves more gradually from coarse to fine.
That does not mean any amount of fines is acceptable. Too much fine material, especially plastic clay-like fines, can make a base hold water or lose strength. Too little fine material can make it difficult to compact.
For base material, the right gradation is a balance.
Example: Concrete Or Asphalt Aggregate
Concrete and asphalt aggregates are typically controlled by written specifications. The sieve analysis is used to verify whether the aggregate falls within the allowed band.
Concrete aggregate gradation affects workability, paste demand, finishability, and economy. Asphalt aggregate gradation helps control the aggregate skeleton, voids, and mixture behavior.
For these products, do not rely on common names alone. A product name like "#57" or "fine aggregate" should be tied to a source and gradation that meets the relevant project requirement.
Because copyrighted standards may define specific numeric limits, it is better to use licensed standards or public agency specifications directly for compliance decisions. Educational blog articles can explain how to read the data, but they should not replace the controlling spec.
Gradation And Drainage
Drainage depends on connected voids. An aggregate with limited fines usually has more open space between particles. Water can move through those spaces more easily.
If the gradation includes too many fines, those voids can fill. Flow slows. In a drainage trench, that can reduce the system's performance. Around a pipe, fines can also migrate and clog openings or fabric if the system is not designed correctly.
For drainage applications, the sieve analysis helps confirm whether the material is clean enough and whether the size range is appropriate for the design.
Gradation And Compaction
Compaction depends on particle packing. A well-graded material can reach higher density because smaller particles fill spaces between larger particles.
This is why base products include fines. The fines are not waste when they are controlled and appropriate for the job. They are part of the compacting behavior.
But compaction is also affected by moisture, particle shape, angularity, degradation resistance, lift thickness, and compaction equipment. Gradation is central, but it is not the only factor.
Gradation And Degradation
Aggregate can break down during production, stockpiling, handling, mixing, compaction, and service. If particles degrade, the gradation changes.
That matters because a material that met gradation when produced may become finer after aggressive handling or heavy compaction if the stone is weak. The result can be more fines, different voids, and altered performance.
Good aggregate selection considers both the initial gradation and whether the material can resist breakdown for the intended use.
Gradation And Blending
Aggregate blending uses sieve analysis data from two or more materials to predict the combined gradation.
The math is a weighted average at each sieve. If one material contributes 60 percent of the blend and another contributes 40 percent, the blended percent passing at each sieve is 60 percent of the first material's percent passing plus 40 percent of the second material's percent passing.
That calculation must be repeated for every sieve. A blend that looks right at the No. 4 may fail at No. 200. A blend that hits a fine sieve may still be too coarse at the top.
This is why a good blend calculator needs the full gradation, not just one product size.
Common Reading Mistakes
One common mistake is reading percent retained as percent passing. That flips the interpretation. Always confirm which view the table uses.
Another mistake is looking only at the top size. Maximum particle size says little about how much sand, dust, or intermediate material is present.
A third mistake is assuming all fines are bad. Fines are bad for some drainage uses, but they are necessary in many compacting base products.
A fourth mistake is assuming a product name guarantees a gradation. Product names help, but sieve data and specifications control.
A fifth mistake is ignoring sampling and stockpile segregation. A test result can be accurate for the sample and still fail to represent the pile if the sample was not collected correctly.
Dry Sieve, Washed Sieve, And Minus No. 200 Results
When fine material matters, ask how it was measured.
A dry sieve analysis can describe the particle-size distribution, but very fine dust can cling to larger particles. If the sample is not washed, the reported amount passing the No. 200 sieve may be lower than the true amount of very fine material. That is why wet sieving is commonly paired with ordinary sieve analysis when the minus No. 200 fraction is important.
In a washed test, the sample is agitated with water so the fine particles separate from the larger aggregate. The wash water is passed through the No. 200 sieve, and the fine material loss is measured. The remaining aggregate is then dried and sieved. This gives a better measure of the fine fraction.
For a drainage stone, this helps confirm whether the product is actually clean. For a sand, it helps distinguish a usable fine aggregate from one with excessive dust, silt, or clay. For a base product, it helps evaluate whether the fines are within the intended range.
The important point is that "No. 200" is not just another row on the table. It may require a different part of the test procedure to measure accurately.
How To Compare A Report To A Specification
When you compare a sieve report to a specification, work row by row.
First, confirm the units and sieve names. A report may use inches, millimeters, U.S. sieve numbers, or a mix. Make sure the rows line up with the specification rows.
Second, confirm the format. If the report is percent retained and the specification is percent passing, convert before comparing. If the specification uses cumulative retained, do not compare it to single-sieve retained values.
Third, check every required sieve. Do not stop once the top size looks right. Many failures are at the middle or fine end.
Fourth, look for missing sieves. If the report does not include a required sieve, the comparison is incomplete. Interpolation can help visualize a chart, but project acceptance should follow the specified test sieves.
Finally, remember that gradation is usually only one part of acceptance. Source approval, durability, cleanliness, shape, deleterious material, and plasticity may also matter.
How The Blend Calculator Uses Sieve Data
The FlintEdge blend calculator uses sieve data to normalize and compare materials across a shared sieve grid. That helps when one source report uses percent passing, another source uses cumulative retained, and a target band uses standard specification sieves.
For a blend, the calculator applies a weighted average at each sieve. If a material is 70 percent of the blend, its percent passing contributes 70 percent of the combined value at each sieve. The same logic is repeated for every material and every sieve.
This is why complete input data matters. If a source report is missing the fine sieves, the calculator has less evidence for the fine end. If the material has changed since the report was run, the calculated blend may not match the current stockpile. If the user enters retained data as passing data, the curve will be wrong.
Use the calculator as a planning and comparison tool. For spec acceptance, the actual blended material still needs proper sampling and testing.
When A "Passing" Gradation Still Needs Caution
A gradation can be inside the band and still deserve caution.
If the curve rides along the upper or lower limit, normal production variation could push it out of spec. If the curve barely passes the No. 200 limit, a small increase in fines could matter. If the curve is inside the band but the material contains clay, shale, soft particles, organics, or poor durability, the product may still fail another requirement.
Also consider the use. A base material near the fine edge may compact tightly but become more moisture sensitive. A clean stone near the fine edge may drain less freely than expected. A concrete sand inside the broad band may still affect water demand or finishability.
The best interpretation combines the curve, the job, and the full specification.
What To Ask For From A Supplier
For simple landscape jobs, a product name and visual expectations may be enough. For technical work, ask for more.
Useful questions include:
- Is the product clean, washed, dry screened, or dense graded?
- Is there a current gradation report?
- Is the material intended for drainage, base, concrete, asphalt, bedding, or decorative use?
- Does it meet a DOT, ASTM, AASHTO, city, county, or project specification?
- How much material typically passes the No. 200 sieve?
- Is the source consistent, or can the gradation shift by ledge, pit area, or production run?
- Has the material been approved for the project or agency?
For engineered work, the project specification should control.
How This Helps With Ordering
You do not need to become a lab technician to order aggregate. But understanding sieve analysis helps you describe what you need.
If you need a drainage product, ask for a clean or washed product with limited fines. If you need a driveway base, ask for a dense graded compacting material. If you need concrete sand, asphalt aggregate, or DOT base, ask for the specific gradation or source approval.
When in doubt, describe the job:
- What is the material going under or around?
- Does it need to drain or compact?
- Will it carry cars, trucks, or heavy equipment?
- Is there a written spec?
- What are the soil and water conditions?
Those details matter more than guessing from a product name.
The Bottom Line
A sieve analysis turns a pile of aggregate into data. It shows how much material is coarse, how much is fine, how the sizes are distributed, and whether the product fits a specification.
The most important concepts are:
- Percent passing means the share smaller than a sieve opening.
- Percent retained means the share held on a specific sieve.
- Cumulative retained plus percent passing equals 100 percent.
- Gradation curves show the full size distribution.
- The No. 200 sieve is a key indicator for very fine material.
- Clean stone and dense base should have different gradation shapes because they serve different purposes.
- Blending must be checked sieve by sieve.
If you have a gradation report and want help interpreting it, send it with the project details. The right answer depends on the data and the job.
Source Note
This article was written from FlintEdge Stone's internal educational library, including aggregate handbook sections on sieve analysis, gradation, particle-size distribution curves, fines, No. 200 material, blending, and quality control. The explanation is original and intended for customer education.