Slag is a super material to use in driveways, underneath flagstone or paver patios, or wherever a hard-packed surface is desired.
Chips and Dust
3/8" and smaller, with many fines. The stone dust mixed in with the chips acts as a binder to help this material pack extremely well. This is a good choice for underneath flagstone or paver patios and walkways, or for filling in between flagstone.
This is a great inexpensive driveway material that packs well. Crushed concrete also works well as a base material for pavers or retaining walls. Made from recycled material.