Crushed Stone and Gravel Sizes: Grades, Uses and How Plants Make Them

Crushed stone is rock quarried from a bench, run through a crusher and separated into size fractions, each sold against a grading specification rather than by the truckload. That distinction carries the whole business. The same granite face can earn concrete-mix money, ballast money or base-course money depending on which screen deck its output lands on, because aggregate buyers do not purchase rock; they purchase a sieve curve with a dust limit attached. Two machines decide where a load lands: the crusher that sets the top size, and the screen that splits the fractions.

The grading system, in one table

North American practice labels coarse aggregate by size number. Each number is defined by the sieve the particles pass and the sieve they are retained on, which is why the ranges below are windows rather than single sizes. The table collects the grades a crushed stone quarry actually quotes and sells; a buyer's written specification always overrides any chart, including this one. The same conventions cover gravel sizes when the feed is river run instead of blasted rock.

Two rows deserve a note. The #57 and #67 numbering looks arbitrary until you see that it is sieve arithmetic: both grades sit on a No. 4 sieve floor, but #57 opens at the 1-inch sieve while #67 tops out at 3/4 inch. The numbers carry no magic; the sieve openings do, and every price in the yard hangs on which openings a plant can cut.

What each size actually sells for

Concrete pays the premium. Ready-mix specifications land on #57 and #67, grades that pack densely without voids large enough to trap bleed water, and whose top size fits the steel: common rules cap aggregate at three quarters of the slab thickness and at the clear spacing between reinforcing bars. A load of washed #57 crushed stone can fetch two to three times the price of ungraded base material in the same market.

Asphalt takes the mid and fine grades. Binder courses run on #57 or #67 for a coarse load-bearing skeleton; wearing courses and chip seals take #7 and #8, where a single-size clean chip locks into the binder film. Shape matters as much as size here, which is why asphalt plants pay for cubical particles and reject flaky ones at the gate.

Road base is the volume business at the lowest price. Crusher run is sold as it leaves under the jaw, fines and all, because the minus-75 µm fraction is not contamination but the binding ingredient: compacted fines lock the interlocking stone into a surface a haul truck can run on. Drainage is the exact opposite trade. #57 or #67 in a French drain is specified clean, often washed, precisely because the 30–40% void space is the product being bought.

Railroad ballast sits in the #4 band, sometimes #3. The specification wants large angular particles that interlock under traffic, drain freely and resist grinding, which is why ballast carries some of the strictest abrasion limits in the industry.

Prices follow the grading in a rough order: washed concrete grades at the top, asphalt chips next, ballast in its own negotiated band, drainage grades below that, and crusher run at the floor. The spread between top and floor in the same yard commonly runs two to four times, which is why plants invest in extra screen decks before they invest in extra crushers.

How a plant makes each size

The jaw sets the top size. Product leaving a jaw tops out slightly above the closed-side setting (CSS), because flat slivers slip through the nip; a jaw closed to 45 mm produces a stream whose largest lumps run near 50 mm. A 40 mm top size therefore needs a CSS around 40–45 mm, and everything coarser in the product is material the jaw never saw. On a tracked plant the logic compresses into one machine: a jaw such as the SE-1060, with a 1,060 × 750 mm opening and a 700 mm max feed, takes shot rock straight from the face, and its CSS becomes the top-size dial for the whole circuit.

The screen does the split. Behind a 45 mm CSS jaw, a three-deck screen with apertures at 40, 25 and 12.5 mm cuts the flow into a minus-40 mm feed, a 40–25 mm fraction, a 25–12.5 mm fraction and a minus-12.5 mm undersize; adding a No. 4 (4.75 mm) deck separates clean stone from the crusher-run-style minus. Each cut is a sellable grade of crushed stone, and the deck cloth choice is effectively the product catalogue.

Moisture changes the arithmetic. Wet feed blinds fine decks within an hour, so plants cutting a clean minus-4.75 mm grade on damp rock run spray bars on the lower decks or move the sizing wet altogether; a screen sized for dry rock will need the next size up once water enters the flow.

Closed circuit makes the fractions clean. Oversize from the top deck returns to a secondary crusher (a cone closed to a 12 mm CSS, for example) and comes back to the screen until it passes. The loop is what converts broken rock into specification stone, me plant open circuit and the top fractions fill with slivers and oversize that gets rejected on delivery. SUHMAN builds the mobile version of this train, tracked jaw to tracked screen, across 22 models rated 50–500 TPH; the ranges are linked at the end of this page.

The last discipline is stockpiling. Grades mixed at the stockpile are grades lost: one loader bucket of crusher run pushed onto a #57 pile can pull the whole pile below spec, and no screen deck downstream will fix it. Each grade gets its own pile, its own loading point, and a loader operator who knows the difference.

The two specs buyers fight over

The gradation envelope comes first. Every specification draws a curve of percent passing at each sieve, with upper and lower limits, and a load of crushed stone outside the envelope is rejected or repriced on the spot. Plants drift out of the envelope for mundane reasons: worn screen panels run the product coarse, a CSS opened by two millimetres shifts the whole curve, a new bench changes the breakage pattern. Sampling every few hundred tonnes is cheap; a rejected shipload is not.

Fines are the second argument, and the direction depends on the buyer. Concrete and asphalt limit the minus-75 µm fraction, often to 1–2% on washed stone, because dust raises water demand and weakens the paste around each particle. Base-course buyers want the opposite and penalise stone too clean to bind. Behind both sits the LA abrasion test, which rotates aggregate with a steel charge and reports percent mass loss; concrete and ballast specifications commonly hold the line at 40% or lower, because the number predicts how the pile will behave after ten years of traffic and weather.

A load outside the gradation envelope is not a discount. jection. Sample before it ships.

Common questions

What size is #57 crushed stone?

#57 passes a 1-inch sieve and is retained on a No. 4 sieve (4.75 mm), so the particles run roughly 5–25 mm with a nominal size near 19 mm. It is the most quoted grade in construction: the default coarse aggregate for ready-mix concrete, the standard fill for French drains and a common driveway stone. Suppliers cut the grade slightly differently, so any spec sheet should still be read against its own sieve table.

Is bigger crushed stone better for a driveway?

No. A driveway needs compacted stability, and that comes from crusher run or #57, not from large stone. #1 or #2 grades leave voids that shift under load and punch into soft ground. The usual build is a base of compacted crusher run with a surface layer of #57; the bigger grades belong under the driveway, in drainage and fill, not on it.

Why does graded crushed stone sell for more than crusher run?

Grading costs money the base product skips: screen surfaces, return conveyors, sometimes a washing stage, plus the stockpile discipline to keep grades apart. The buyer pays for certainty. A concrete producer batching #57 can design the mix from the sieve curve; against crusher run the curve is whatever the jaw left that day. The premium is the price of a curve that stays put.

Where the equipment decides it: the machine that sets top size and the machine that cuts the grades are the jaw crusher and screening plant ranges, and closed-circuit cone work on abrasive rock is on the cone crusher page. At the fine end of sizing, where grain windows replace stone grades, see what silica sand is; for the money side of the machine that starts every flow, the jaw crusher price guide lays out the buying math.