Cob vs Pise and just a little bit about plasters

[patrick newberry]

Pise / rammed earth has about 10% cement mixed in with it.
Does anyone think this has any significant advatage over (strengtht or
otherwise) cob.

I was told in the strawbale list that puting cement on the outside of a some
earth plaster, the moister would be trapped in the earth plaster.
I was told that  many of the adobe buildings out west have been damaged
because of the application of cement to the outside of the buildings. 

what about a pise like substance that is 10% cement mixed in with the earth
plaster to add some more strength but still retain some of it's breathability. ?