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[SB-r-us] Re: GSBN:Jeff Ruppert and clay tests
I have posted this to both groups as the material contained here has
appeared in both forums.
I think I can clear up some of the confusion at least when it comes to
Bruce's comments about lime weakening clay by deflocculating it. What
he says is true in that small amounts of lime agglomerates the clay
particles and makes them resemble silt sand size particles. Basically
it trashes the clay. It can't bind anymore nor does it hold onto
water. It's a long explanation that doesn't need to happen here at the
moment. Basically the intent is to take away its ability to expand and
shrink so drastically. The big "however," in this case is that if one
adds enough lime to get the pH of the clay/lime mix up in the vicinity
of 12+, then different things happen, the silica in the clay begins to
break down into gel and recombines with the calcium to make a new
substance that is stronger and more water resistant the original clay.
Then, instead of modifying the clay, it truly becomes a "stabilized"
material. The key is adding enough lime, anything short of that makes
it weaker. Now when Bruce talks about our early experiments producing
weak bricks, that was true, but somewhere back a ways we essentially
figured out that what was needed was more lime. Harry Francis says
somewhere around 10% by weight is about right if you're just shooting
in the dark and not using pH meters or doing tests on individual
samples. My experience at this point says that seems about right.
We've got what I would consider some incredible samples of the stuff at
the moment that I am very pleased with, there isn't much more you can
ask of a plaster at least in this environment. So I haven't ploughed
through all of Paul Lacinski's earlier post but I would suspect that I
would agree with most of what he has said there.
For the meantime, if you want more info on this, I posted the article
Harry wrote for issue no. 22 of TLS (Lime Plaster) which deals with the
Stabilization of Earth with Lime. If you have issue 22 still around,
you can find it there. Otherwise, it is under the files section of the
SB-r-us group site.
And I guess whoever is interested in testing this stuff ought to talk
with Harry cuz he claims to have had in his hands samples of lime
stabilized clay that had compressive strengths exceeding 1500 psi. Now
what to say, either Harry is suffering from confusion, bad memory,
wishful thinking or there might be a chance that he is telling the
truth. Just in case he is, I think we ought to find out what
particular combination produced those results, where, when and what
have you. Or at least so it would seem to me.
One concern I have always had about this particular combination is
wondering how efficient it would be in not letting liquid moisture pass
through to the straw. Clay obviously likes to hold onto it and not let
it go, cements, limes by themselves appear ready to give it up at a
moment's notice. So I have wondered where the clay/lime mixes would
stand on that scale. According to Harry (one more time) what happens
is that as the calcium silicate forms, the interparticle spaces are
filled with crystalline grow of CaS making the material impermeable
....filling up the voids, and making the new material as water tight as
was the clay....and yet at the same time, clay and lime combined do not
attract moisture. Having attempted to soak and erode some of the walls
we have here, it always seemed to be the case, that they were doing
exceptionally well in resisting the uptake of water and apparently
that's the case.
On Wednesday, January 8, 2003, at 05:35 PM, Paul Lacinski wrote:
> Responses below to emails from both Bruce and Tim:
>> Clay by itself is the binder in earthen plasters, and as we all know,
>> really well when done right. Lime, on the other hand (and portland
>> will destroy clay's binding force by deflocculating the little
>> grains. That's why highway builders, especially in wet climate/clay
>> places like the UK, like to use lime to both dry and deflocculate
>> before laying down their beloved asphalt paving.
> I'm not sure, but I think you have it backwards- I think the lime
> causes the clay particles to glom together. My copy of the lime books
> are out on loan, at the moment, however. I do know that if you have a
> clay plaster going in the mixer and you start adding lime, you
> eventually hit a point where the mix suddenly gets very stiff, stiff
> enough that if you don't immediately add water the paddles are likely
> to stop turning and the breaker to pop. At this point the mix also
> becomes very greasy. I'm not sure, but I think this is a decent field
> test for the minimum amount of lime to add to a given batch of clay.
>> That's also why Bill
>> reported LOSING strength in earthen bricks when he added lime; his
>> wasn't binding, which will always put a hitch in ol' Bill's giddyup.
>> that's only the short term (one or two month) picture . . .
>> . . . The long term picture has the lime carbonation and low-grade
>> pozzolanic reaction between clay and lime coming into play, and I'd
>> the strength/durability would keep on growing over the years.
> This has been our experience, exactly. The clay/lime mix is noticably
> stronger after 4 or 6 months than after 1 month. At 2 weeks or 1
> month, it may well be weaker than the clay-only mix.
>> Recently I was afforded an
>> opportunity take apart some of these assemblies. (more on that later)
>> notably the earth to lime connection was the week link and I would
>> extreme weather would like to pop the thin lime coat off. for this
>> (and the mold that Paul mentioned) I am interested in getting a small
>> of lime into the mix and work it to the surface then scratch so that
>> I might
>> have a better chance of getting a lasting bond. I have not noticed
>> degradation of the brick clays but site soils do all kinds of things
>> that I
> don't fully get yet.
> Everyplace I go, I bring my building geek self along, and look for
> delaminating plaster. It's not hard to find, but I have never found
> it in a situation where the backing coats were scratched, regardless
> of material. This doesn't mean it can't happen; but it's clear that
> scratching greatly reduces the likelihood.
> When we next plaster (March) I'll make a raft of samples, and send
> them along for testing. I can also send the 2x2x8 blocks that Tim
> recommends. The best may be to test at 1 month, two months, and 4
> Paul Lacinski
> Amy Klippenstein
> GreenSpace Collaborative
> Sidehill Farm
> PO Box 107
> 463 Main St.
> Ashfield, MA 01330 USA
Athena & Bill Steen
The Canelo Project
HC1 Box 324
Canelo/Elgin, AZ 85611
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