[Cob] cob in post and beam

[Lance Collins]

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Hi,

I'm just a list following junkie here with no specific experience.   But I 
clearly recall a posting a few months ago which quoted equilibrium moisture 
levels for various materials.   Concrete had the highest moisture retention 
at about 20% and adobe was quoted at 4.5% having the lowest moisture level.

>Forward to group:
>
> >Rebar in concrete allowed to rust, weakens the
> >structure and has been the cause of buildings
> >collapsing, due to the exposed rebar which rusted
> >through (eating through (oxydizing?) by moisture and
> >air by)

Yes but the whole idea with reinforced concrete is to cover the rebar with 
enough concrete to stop moisture getting to the rebar and causing concrete 
cancer.  Usually this is about an inch for concrete.  I don''t know how 
much for cob but I would think that a moisture level in cob high enough to 
rust steel would also be high enough to cause the cob to fail in a short 
time anyway.



> >Cob, modifies moisture in dwelling and can hold more
> >moisture than concrete walls.
>
> >So rust proof materials would be a solid decision for
> >humid areas.
>
> >Darel
>
>--- David Knowlton <pilot1ab80 at hotmail.com> wrote:
> >> rebar in concrete is allowed to rust. rough oxide
> >> provides a nice
> >> grip for the concrete. just a thought
> >>

I think what was meant was that the rebar is allowed to rust before 
installation not that rusting continues after construction.


Lance Collins


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