ASTM D448 — aggregate size numbers

Two families, two standards

ASTM D448 — Standard Classification for Sizes of Aggregate for Road and Bridge Construction — defines the numbered gradations. AASHTO M43 is its parallel. These cover clean, open-graded stone: single-sized, washed, fines removed.

AASHTO M147 and ASTM D2940 cover dense-graded base material — crusher run, aggregate base course, ABC, QP, DGA — where the fines are deliberately retained.

These are not two points on a scale. They are different specifications for materials that do opposite jobs, and asking a yard for "gravel" gets you whichever is nearest the loader.

That 0–10% passing the #4 sieve is the whole story. With almost no fines there is nothing to fill the voids, so water passes freely — and so the material cannot be compacted to a density in the way a base course can.

The US Federal Highway Administration is explicit: compaction control for open-graded aggregates is method-based — compact to non-movement — rather than a percentage of a Proctor maximum. The Proctor test does not meaningfully apply to a material with no fines.

These are among the few measured figures on this site. Most aggregate densities in circulation are trade convention; the #57 numbers come from an FHWA study of open-graded aggregates, which is why our #57 page is more confident than our dense-graded pages and says so.

• #57 and #67 are for drainage — French drains, pipe bedding and backfill, drainage blankets, and the reservoir under permeable paving. In Britain, ask for 20 mm clean or washed shingle; #57 is an American designation and UK yards do not use it.
• #57 is wrong under conventional paving or a driveway. It will not lock up, and the surface above it moves. Use dense-graded crusher run or MOT Type 1.
• Crusher run is wrong in a French drain. The fines block it. This is the commonest French drain failure and it is invisible on the day it is built.
• Do not accept "20 mm to dust" when you asked for 20 mm clean. The words are similar and the materials are opposites. If you can see dust on it, it is dense-graded.

An honest note on edition years

We do not publish edition years for ASTM D448 or D2940. Both are behind a paywall and we have not verified the current designations. Rather than guess a year to look authoritative — which is precisely the habit this section of the site exists to call out — we cite the designation without one. If you need the current edition for a specification, buy it from ASTM.