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Re: GSBN:test results
- To: "GSBN" GSBN@...
- Subject: Re: GSBN:test results
- From: Athena & Bill Steen absteen@...
- Date: Wed, 2 Oct 2002 08:28:44 -0700
- Reply-to: "GSBN" GSBN@...
- Sender: "GSBN" GSBN@...
Once again, I would echo these comments. And I would add something that
hasn't come up yet as a possibility and that they the method(s) used for
testing. In that I don't recall exactly what the procedure was, could
it be that there were errors in the way the testing was carried out?
On Monday, September 30, 2002, at 03:30 AM, Paul Lacinski wrote:
Well yes, I find this just as perplexing as everyone else, since it
contradicts my experience just as directly as everyone else's. Here's
what I did for a test: I brought a piece of an old chair around to the
back wall of our house, which is partially covered by a lime-stabilized
clay plaster, about 1" thick, and partially covered by this same
plaster with a 3/8" lime/sand finish coat. (The system that we always
use.) I then attempted to gouge these two plasters with the corner of
the chair, mimicking, as best I could, a portly and slightly drunk
matri or patriarch jumping up from the table to answer the door or
phone or whatever. And what do you know, the lime-coated wall is much
more resistant to this type of abuse than the clay-only wall.
So, having re-examined the field conditions, I am led to wonder what
might possibly have been different about the lab conditions. The only
idea I have is that 2" is much thicker than I would ever go with lime,
without a pozzolanic additive. (We have poured 2-3" thick lime
concrete with ground bricks or pottery as a pozzolan and come up with
compressive strengths that, while never tested by the psi, are
definately much better than could ever be achieved with earth.
(Children jumping around on windowsills made of this material seem to
have no effect.) I know what when you pick up a chunk of dropped lime
plaster that has been sitting around for a few weeks at the base of a
wall, the surface (3/8" or so) will be well set, while the material
below will be quite weak. I've gouged these limeplops with a
screwdriver before, just to see. The surface is about as hard as a
finshed plaster; the underside is not much better than the gypsum in
So, maybe we have a situation where the lime didn't cure much, except
on the surface, and the cement dried out too quickly to cure
properly. If there are any samples left intact, it would be
interesting to go at them with an awl or screwdriver, to test this
theory. Also- is there any chance it was a bad batch of lime? Was the
bag of lime left around the lab for awhile before it was used? Was it
leftover from a site somewhere? Is there any chance it got damp?
Maybe someone could look at a bit of this material under the special
microscope (whatever it's called) to check on the cement crystal growth?
In any case, thanks again for all of this work. Whether or not I like
the outcomes, I'm very happy that the sb world is moving beyond testing
plasters with the back of a chair.
-- Paul Lacinski
PO Box 107
463 Main St.
Ashfield, MA 01330 USA
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