CA6 Gravel: What It Is and How Much You Need

CA6 gravel is a dense-graded crushed stone used as a compactable base under driveways, patios, slabs, and pavers, especially around Illinois and nearby states. The name comes from the Illinois Department of Transportation’s coarse aggregate gradation numbers. CA6 contains stone up to about an inch along with smaller pieces and fines, so it packs into a hard, stable layer. In the Chicago area it is often sold as “grade 8” or crushed limestone base, while elsewhere similar products go by crusher run or dense-grade aggregate.

Volume and tonnage calculator →

What CA6 looks like

Top size: roughly 1 inch, with a range of sizes down to fine dust.
Material: usually crushed limestone or dolomite, sometimes recycled concrete (often called recycled CA6).
Texture: angular pieces that interlock when compacted.
Color: gray or tan depending on the quarry.

Gradation details depend on the current specification and the supplier, so ask for the product sheet if a project has strict requirements.

CA6 vs CA7

Product	Gradation	Main use
CA6	Dense-graded with fines	Compacted base for driveways, slabs, and pavers
CA7	Clean stone, roughly 3/4 to 1 inch, no fines	Drainage, backfill, under permeable surfaces

CA7 drains freely but does not lock together the same way. Many projects use CA7 around drain tile and CA6 where a firm, compacted surface is needed.

Weight and coverage

Compacted CA6 commonly weighs roughly 1.4 to 1.5 tons per cubic yard, and loose material somewhat less. A ton typically covers around 80 to 100 square feet at 3 to 4 inches thick, depending on compaction.

Area	4-inch base	6-inch base
10 x 20 feet (200 sq ft)	About 3.5 to 3.7 tons	About 5.2 to 5.6 tons
12 x 50 feet (600 sq ft)	About 10.4 to 11.1 tons	About 15.6 to 16.7 tons
20 x 50 feet (1,000 sq ft)	About 17.3 to 18.5 tons	About 26 to 27.8 tons

Add 10 to 15 percent for compaction and waste. The base tonnage calculator handles other sizes.

Common uses

Driveway base under asphalt or as a gravel driveway surface.
Slab base under concrete patios, garages, and sheds.
Paver base, compacted under a bedding layer of sand or fine stone.
Trench backfill where compaction is needed.
Pole barn and building pads.

Installing CA6

Remove topsoil and soft material.
Lay a separation fabric on soft or clay soils if needed.
Spread CA6 in lifts of about 2 to 4 inches.
Lightly moisten and compact each lift with a plate compactor or roller.
Grade for drainage, crowning driveways so water sheds to the sides.

See compacting gravel base in lifts for technique.

Bottom line

CA6 gravel is an Illinois-standard dense-graded crushed stone with fines that compacts into a firm base for driveways, slabs, and pavers. Plan on roughly 1.4 to 1.5 tons per compacted cubic yard, add extra for compaction, and compact it in thin lifts.

Questions people ask

What is CA6 gravel?

A dense-graded crushed stone with fines, about 1-inch minus, used as a compacted base, named under Illinois DOT gradations.

Is CA6 the same as grade 8?

In the Chicago area, grade 8 is commonly used to describe CA6-type base stone. Confirm with your supplier.

How much does a yard of CA6 weigh?

Compacted CA6 commonly weighs about 1.4 to 1.5 tons per cubic yard.

What is the difference between CA6 and CA7?

CA6 has fines and compacts firmly; CA7 is clean stone without fines that drains freely.

Can CA6 be used for a driveway surface?

Yes. It compacts into a firm surface, though it can be dusty and may need topping up over time.

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