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Crushed rock

Crushed rock vs crusher dust vs aggregate: what is the difference?

Three products, three jobs, and a lot of confusion. Order the wrong one and it either will not compact or will not drain. Here is how to tell them apart.

Plain-English guideVictorian specs & unitsUpdated June 2026
Quick answer

Crushed rock is a graded blend (big stones down to dust) that compacts into a hard base. Crusher dust is just the fine end, used as a bedding and packing material. Aggregate is clean, single-sized stone with no fines, used in concrete and drainage.

The simple rule: crushed rock to compact, crusher dust to bed, aggregate to drain or batch into concrete.

The one thing that separates them: fines

All three come out of the same crusher. What makes them different is how much fine material (the sand-and-dust end) is left in the mix, and that one difference decides what each can do.

01Crushed rock keeps the full range of sizes, from the top stone down to dust. The fines fill the gaps, so it locks up and compacts.
02Crusher dust is the fine end on its own (around 5mm and smaller). It packs tight and binds, but has no large stone for strength.
03Aggregate is screened to a single size with the fines washed out. With nothing to fill the gaps it stays open and free-draining, but it will not compact or bind.

Side by side

Crushed rockCrusher dustAggregate
Contains fines?Yes, full gradingYes, it is the finesNo, washed out
Compacts?Yes, locks up hardPacks firmNo, stays loose
Drains freely?NoNoYes
Typical sizes20mm, 40mm5mm minus7, 10, 14, 20mm single
Best forBases & pavementsBedding & packingConcrete & drainage

What each is used for

Crushed rock (road base)

The foundation layer under driveways, paths, slabs and roads. Spread, watered and rolled, it becomes a hard, load-bearing base. This is the product you want anywhere something has to be driven or built on. See what is road base.

Crusher dust

A fine, compacting material for bedding under pavers and pipes, packing around tanks, and as a binding fill. It screeds to a smooth, even bed and packs tight, but because it holds fines it does not drain, so keep it out of places that need water to move through.

Aggregate

Clean, single-sized stone for mixing into concrete, surrounding ag-drains, filling soak wells and any job where free drainage matters. Because it has no fines it stays open and lets water through, but for the same reason it will never compact into a firm base.

Quick "which do I need"

01Building a base to drive or build on, that has to be firm: crushed rock.
02Laying pavers or bedding a pipe, or packing around a tank: crusher dust.
03Mixing concrete, or backfilling a drain so water moves: aggregate.
Still not sure? Send us what you are building with your quote request and we will tell you exactly which product, and how much.

Common questions

Can I use crusher dust instead of crushed rock for a base?
Not for a load-bearing base. Crusher dust packs firm but has no large stone for strength, so it is a bedding and packing material, not a pavement base. For a driveway or slab base you want graded crushed rock, which has the stone and the fines to compact hard.
Why will aggregate not compact?
Aggregate is screened to a single size with the fines washed out, so there is nothing to fill the gaps between the stones. It stays loose and free-draining, which is exactly what you want for concrete and drainage but useless for a compacted base.
What is crusher dust best used for?
Bedding under pavers and pipes, packing around water tanks and conduits, and as a binding fill. It screeds flat, compacts to a firm even surface and holds its shape, which makes it the go-to bedding material.

Related guides

What is road base? How much does crushed rock weigh? How much road base do I need?

The products

Crusher dust 10mm aggregate Class 3 20mm crushed rock

Right product, right quantity, one call.

NXT Quarry supplies crushed rock, crusher dust and aggregate across Victoria. Tell us the job and we will match the material and track it to your gate.

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