#57 stone vs crusher run — open-graded drains, dense-graded compacts

What this diagram shows

A side-by-side cross-section of #57 stone versus crusher run, the two most common ¾-inch crushed stones. On the left, open-graded #57 has only 0 to 5 percent fines and about 40 percent open voids, so rainwater drains straight down through the gaps to the subgrade, but it never locks into a load-bearing base. On the right, dense-graded crusher run (also called ABC, DGA, or 21A) has 10 to 20 percent fines packed into the voids, so it compacts to a stable base, but water ponds on top and runs off. Each grade’s strength is the other’s weakness: use #57 where water must pass, such as French drains, drainage backfill, and driveway top course; use crusher run where you need a compacted base, such as under pavers, slabs, and driveways. Substituting one for the other clogs the drain or ruts the base.