Base for concreting on

"Cracker dust" or "crusher dust" is the go around my area - as advised by all the concreters & bobcat drivers I've used for various work over the years.

This "cracker dust" is actually recycled concrete from a local recycling plant. It goes down easy, can be raked, then wacker-packed, and if you wet it down, it goes crusty & hard, providing a great base.

I put 450mm of it down in one area, under a 5 x 8m slab (dug out heaps of sloppy, wet clay) and packed it well between truckloads, and in 8 years that slab never cracked.

It's also providing a 150mm (and deeper in some spots) base for my old driveway (around 120sq m) and it's only ever copped 1 hairline crack across it, which started at a 270 degree brick corner - an area prone to break.

I read a bit on that cracker dust nut. it is supposed to be great stuff. It also makes a better use of building waste (even though a shinto load of energy is used to re-manufacture it )