What kind of dirt...

[jerry56]

Ok this is probably a stupid question but I'm planning an outdoor construction site. The ground where it's going is hard clay and doesn't dig easily so I'll need to bring in something.
I considered sand but I wondered about sand in my converted Bruder tracks might be way to abrasive. I thought about stone dust but wondered if it might pack to hard. Of course I could go with topsoil, or a topsoil mix we can get here that is pretty light and drains water really well but doesn't hold together well for digging or trenching...
I thought about a combination of sand and topsoil or sand and the top soil mix...
So what is the consensus of what makes a good RC construction site. My equipment is all Bruder dozers and loaders and Tonka truck and crane conversions, I may get a Huina excavator at some point no plans for hydraulics at this stage of the game