Alternatives to clay in cob

I have some land in south central Oregon, east of Klamath Falls, thay has volcanic ash/sandy soil. In my initial tests there was almost no clay. If I want to build with cob, are there alternative additives to clay?

Thanks for any input.

I’ve always wondered about cow pies.. out here in the desert they dry out and get really solid. Maybe get them fresh, or rehydrate them and stack it just like you would cob. Definitely want to plaster it, as cow pies tend to burn real well.

How Far East of Klamath? I’ve lived out in Lake County in the past..

Without clay it is not cob. Matter of definition.

You probably want to research pozzalans and geopolymers. You may have the ingredients for some of the recipes in those areas, which might get you even further along than cob could.
It's a pretty deep and fascinating rabbit hole ;)

Lime, bagged clay or if you can get chocolate loam by the yard from a landscaping supplier. My cob mixes only use 10-20% clay so little will go a long way.

Hello, I live along the McKenzie River in Oregon (just west of the cascade crest). My area is affected by fires and has volcanic soil. I would guess it’s not dissimilar from Klamath. How I make cob without clay is either by adding manure (the boring way) or by collecting the talc like soil in the ditches of burn scar areas to add to my straw and soil (the fun way). The best runoff happens when I see open patches of white basalt rocks, My suspicion as to why this works so good is because it’s probably some natural cement/lyme. I build random cob things all year long and the manure version is better suited for building in the summers and the burn scar runoff version is better suited for the wet seasons.

An experienced earth builder in this region uses paper pulp as an additive for lime plasters. It might also work to bulk up a clay-deficient cob mixture. I've worked with some of his pulpy plaster mix and it's really forgiving.