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Re: GSBN:Jeff Ruppert and clay tests
Happy New year all,
OK, I've been waiting until I had enough time to weigh in on the clay chat,
but that may never happen so here is a rushed response. Hopefully I'll
follow up sooner or later with more detail and questions.
most importantly, Paul, or anyone else who wants to, if you are going to
send cubes also send 6 bricks 2x2x8in. that way we can also test for modulus
we've tried (on buildings) 20 different mixes of earth based plaster and
more than 15 soil types and we're still pretty low on the curve. We used to
add up to 1 part lime per clay but because of the variability in how it
performed with different soils. We have moved to using either lime or earth
plaster or lime plaster. though we tend, like many of you to add a top lime
coat on the exterior of our earth plaster. Recently I was afforded an
opportunity take apart some of these assemblies. (more on that later) most
notably the earth to lime connection was the week link and I would assume
extreme weather would like to pop the thin lime coat off. for this reason
(and the mold that Paul mentioned) I am interested in getting a small amount
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 much
degradation of the brick clays but site soils do all kinds of things that I
don't fully get yet.
After working with the lime-earth plasters at 1:1 I feel we are actually
making a weak Lime plaster rather than a stranger earth plaster - that's why
we're testing it. I have cast samples of a 10% lime in earth mix and a 50%
lime in earth mix which we will break this month as part of the EBNet
testing program. We are also sending samples of each mix to John Straube to
measure the permeability. (Bruce, we were mixing them for John and decided
to cast cubes as a bonus). Also, Paul, what lime are you using and how are
you preparing it?
We have also been working with crusher fines of late (the same source that
is used for most rammed earth in Northern California). we have been able to
make a good mix with adding only small amounts of brick clay and a healthy
amount of straw. My main concern is determining the silt content of the
fines because I think the bulk of the silt in the fines masquerades as clay.
we've been happiest with two mixes: 4 crusher fines, 1 brick clay, 2 sand, 3
chopped straw; for sprayed plaster, and 6 crusher fines, 1 brick clay, and
3-4 long straw, for one coat hand applied mixes or for cob. We mix both in
our 10 yd horizontal silage mixer (we bought the smaller one) and the second
mix we just through whole bales in and it chops it pretty well.
I have done cylinder tests of the second mix that show a possible 400 psi. I
am about to test it more formally because we may have had too much local
containment on the cylinders.
For those of you who want to submit "food for Jaws", we will be happy to
accept them and test them if we can but no guarantees.
I feel that the Earth plaster that we are using in the testing program is
fairly weak though not unrepresentative of what I've seen. As Bill and
Athena noted when they were out it is fairly silty as are most of our clay's
in CA. As the King has intended we should have a fairly simple protocol for
testing any earth plaster when we're done and that's what's really exiting
Natural Building and Design, inc.
3212 Jefferson St. #406 Napa, CA 94558
----- Original Message -----
From: "Bruce King" ecobruce@...
To: "GSBN" GSBN@...; "Tim Kennedy"
Sent: Monday, January 06, 2003 5:19 PM
Subject: Re: GSBN:Jeff Ruppert and clay tests
> on 1/6/03 11:41 AM, Paul Lacinski at paul@...
> > Many thanks for this test. We use clay and lime plasters almost
> > now, but I am still uncomfortable promoting them without solid data . .
> > . . . My concern about this mix is the degree to which vapor
> > may be reduced. In Building with Lime, Michael Wingate and Stafford
> > talk about a low-grade cement being formed by the reaction between the
> > and some of the minerals in the clay. This is only one of a set of
> > that supposedly combine to form the harder plaster. The
> > (sticking-together) of the clay particles, pozzolanic reactions between
> > lime and minerals in the clay, standard carbonation in the lime- don't
> > if they would cause significant reductions in vapor permeability.
> > nature of these reactions would certainly vary according to the
> > clays and limes used, it would be useful to have some general sense of
> > this plaster would perfom, compared with the clay-only version.
> Paul, Jeff, and all y'all -
> Bill Steen (and others) and I have had a slow running conversation on this
> subject over the years. There are so many kinds of clay, occuring in so
> many proportions in various natural or bagged soils, and also so many
> of lime with varying degress of hydraulicity (ie similarity to portland
> cement) that it's maddening to try and extract generalizations about
> lime-clay behaviour.
> But hey, while we're young and foolish, let's try!
> 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 soil
> places like the UK, like to use lime to both dry and deflocculate soils
> before laying down their beloved asphalt paving. That's also why Bill
> reported LOSING strength in earthen bricks when he added lime; his binder
> wasn't binding, which will always put a hitch in ol' Bill's giddyup. But
> 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 guess
> the strength/durability would keep on growing over the years. I would
> guess that vapor permeability would decrease, but not very much.
> > So, I hope you find this useful. If anyone has any ideas or needs more
> > specific thoughts or mixes, please let me know. And maybe someone who
> > laboratory-oriented than myself wants to crush a few samples? I'd send
> > virtual kiss for that, which you are absolutely free to refuse!
> Well, gee, Paul, yer mighty cute and all, but I'll pass on the smooch. We
> do, however, have a reasonably accurate rig now set up (part of the EBNet
> testing program) that can crush plaster cubes. We affectionately call
> little hummer "Jaws", and would be happy to put it to use. How about,
> Paul, you make up a dozen or more 2" cubes each of your clay plaster and
> lime-clay plaster, let them set a month or two, and send them out to the
> address below; we'll squish 'em and report the results. Paul, if you do,
> write EVERYTHING down: mix proportions (including water), description of
> ingredients, cast dates, method of curing (under a tarp inside in
> conditioned space is ideal), etc.
> By the way, on Jeff Ruppert's website, he makes reference to the "300 to
> psi strengths" obtained in the EBNet program. Due to the bonehead error
> an arithmetic-impaired engineer who shall remain nameless, those numbers
> erroneous in that said engineer forgot to divide by 4 (ie the four square
> inch area of the 2" cube). Anyway, the numbers (87 to 200 psi) are now
> correctly reported on the EBNet website, and said engineer has been
> of his pocket protector for three months.
> Happy New Year to all
> at least as much as is possible under the shadow of a Bush,
> Bruce King, PE
> Director, Ecological Building Network
> 209 Caledonia St.
> Sausalito, CA 94965
> (415) 331-7630
> fax 332-4072
> bruce@ ecobuildnetwork.org