It can be used for
COB or anything you want. There
should be some clay in it, do a jar and block test. If not add a natural polymer like lime, if that is not
enough add some portland cement too or fly or
wood ash. Rammed Earth take to it well I bet. I'd have a passive radon mitigation and be active ready.
I'm in San Diego when I'm not on the road working

Paramount Natural Design-Build Architect, Engineering Services, GC, LLC.