Oh, that's awesome. We have a pretty crappy clay here, but I will ask my buddies that work building roads in the bush. They might come across a site that has some good stuff. Most of the rocks are round, but I was going to use mortar and sand to build it up a few feet. There is a spot that has a lot of shot rock from a mountain, and we plan on going camping near there this summer, so we'll take the trailer in and pull any good squared off pieces out with the quad. It's almost like granite, so it should be pretty good if we can get to it without the quarry guys catching us. It's in a blast site that they are getting riprap for the dam face, but the blasting is all done now.
The driftwood trees that float in will be really good for the beds, I'm thinking.
I looked up air crete and it looks pretty amazing. I'm going to research more, but it looks like it's just really wet cement mixed with dish soap foam. I don't know what the chemical composition is, but whatever is in Dawn dish soap and the cement you use.