Overburden is the gravelly, claggy stuff dug up around the main aggregate in a quarry. It can be used as a binding foundation for paths.
Syra is a woodland forest garden project on the west facing side of a Carmarthenshire hill. Matt and Marley from West Wales Trails are creating footpaths & seating areas, for access and management.
I was asking Matt about a cheap alternative to sub-base for the self-binding gravel I’ll be using in the Primary school wildlife forest garden.
The problem with using hardcore from builders rubble is that it can contain all sorts of aggregate. Matt suggested asking local quarries for overburden, the earth around the edge of the material being quarried. They might even grade it.
Footnote: I’m not a big fan of mining generally but if there’s a way to use existing “waste” material, then I’m all for it.