Rethink Your Life!
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The Work of Art and The Art of Work
Kiko Denzer on Art

[Cob] straw in cob or concrete?

Lance Collins collinsl at
Thu Aug 14 16:06:49 CDT 2008

>Have you ever gotten concrete on your hands?  It is highly caustic,
>dissolving all carbon straw doesn't have a chance!

I've found wood pieces in old concrete still in excellent condition.

>Concrete guys will throw in bags of loose poly-fibers (plastic) which
>are supposed to prevent cracking in slabs...

It does work.  The people on the ferro-cement list are very positive 
about PVA fibres.

>But rebar even doesn't hold out forever, because concrete acts as a
>wick, drawing whatever moisture hits it straight in - rusting the
>rebar and causing collapses of bridges, etc...

This only happens to poorly built structures or those attacked by 
de-icing chemicals.

I've broken old weather-exposed concrete where the rebar was as shiny 
as the day the concrete was poured.

>Now they coat the rebar
>with epoxy or plastic, then pour the concrete over it.

Thst's safer but unnecessary if you get the concrete mix right.

The above comments on concrete are analogous to saying that cob 
building can't work because the cob will turn to mud when it rains.

(in Aus)