[Cob] Super adobe: was Arches

[Lance Collins]

Shody wrote:

>I agree about the difference between cob and adobe but
>I think super adobe is different due to 6% portland
>cement which hardens by hydration as opposed to cob
>and adobe by evaporation. I assume cob is usually
>slightly acidic depending on the site and cement
>alkaline.

I don't know where 6% comes from but it's a useless figure out of context.

Where I lived years ago 6% with my sandy soil made fairly soft but 
quite good concrete blocks.
Where I am now I need to add over 10% cement to get a result 
noticeably different to a simple puddled block with no 
cement.  There's nothing 'super' about it.

The properties of soil vary enormously from place to place.   The mix 
for any building technique including soil must be site specific.

I would suggest that anyone pushing a mixture of soil and some 
additive and describing it as 'super' should treated with caution.

Lance
(in Aus)







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