[GSBN] Steel mesh in clay plaster (?)

[martin hammer]

Thanks Misha.  More good anecdotal information.

The attached movie didn¹t play for me.  Normally I can play .mov files.
Don¹t know if others had the same problem.  Had a file size of only 4 kb.
Can you look into this?

Martin


On 8/25/13 11:05 AM, "Misha Rauchwerger" <misha.rauchwerger at gmail.com>
wrote:

> Hi Marty, et. al.,
> 
> I have some anecdotal information to share.  I just did a small demolition of
> a window in a cob structure.  I've attached a short video of some of the
> demolition.  There was galvanized expanded metal lath on the underside and
> vertical faces of a header that was embedded in the cob.  The window was
> constructed approximately 17 years ago.  I was really impressed with the
> tenacity of the cob, especially to the horizontal underside of the header,
> which you can see in the video of me using a small jackhammer to remove it. 
> Some old nails were also used for connection.  With regards to corrosion,
> after 17 years, the lath had a minor amount of rust, but appeared to have
> stopped, looking superficial.  There did not appear to be any difference in
> amount of corrosion on the lath just under a thin layer of plaster on the
> exterior face of the header, versus the corrosion on the interior lath.  I
> have a feeling that once the cob dries, there is a minor amount of shrinkage
> away from the metal, so even if it is still mechanically attached, there is a
> small air space which limits the corrosion unless moisture is re-introduced to
> the lath/earth interface on a regular basis.
> 
> thanks for all your work on the subject.  I'm excited to do further research
> with Art Ludwig with regards to FerroCob, as our scale model of a FerroCob
> house had incredible performance on our small testing jig.  We'll keep you
> posted.
> 
> Misha Rauchwerger
> www.builtinbliss.com <http://www.builtinbliss.com>
> 
> 
> 
> 
> On Sat, Aug 24, 2013 at 1:39 PM, martin hammer <mfhammer at pacbell.net> wrote:
>> Hello all,
>> 
>> Can anyone weigh in on the use of steel mesh in clay plaster, in terms of
>> corrosion of the steel?  In particular if it is susceptible to a higher rate
>> of corrosion than steel mesh in lime or cement plaster (or what an expected
>> service life might be).  Laboratory tested evidence is especially welcome,
>> but so is anecdotal evidence (pro or con).
>> 
>> I know there has been concern expressed about this for many years.  I¹ve
>> heard theory, but I haven¹t seen hard evidence that it is actually a problem.
>> 
>> I ask this in the context of a Strawbale Tutorial I am co-authoring for the
>> World Housing Encyclopedia.  The tutorial is meant as guide for constructing
>> small houses in seismically active regions of the developing world.  Thus the
>> desire for a reinforced clay plaster as the in-plane lateral resisting
>> system.  Darcey Donovan has used nylon fishing net in her system with PAKSBAB
>> in Pakistan (which was shake table tested) but I am looking to use other mesh
>> materials where such fishing net might not be available.  Metal mesh seems to
>> be readily available in most of the developing world. (We are also
>> considering natural fiber mesh, but these may have strength and degradation
>> problems). 
>> 
>> Thanks!
>> 
>> Martin
>> 
>> PS ­ I¹ve copied my colleague, Dmitry Ozeryansky, PE
>> 
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> 
> 
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