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Re: GSBN:Recap on what I learned on lime



Excellent summary Andre, some addition on the sand:
sharp sand (washed) 1. layer 0.4 mm, 2. layer 0.4-0.3 mm, 3.. layer 0.2
mm...

The hydraulic part in the NHL can vary due to the mixture in the used
limestone, that's why asking the manufacturer for specification.

Greetings,

Martin


----- Original Message -----
From: forum@...
To: "GSBN" GSBN@...
Sent: Tuesday, December 14, 2004 10:33 AM
Subject: GSBN:Recap on what I learned on lime


> In Europe we distinct 2 types of (natural) lime:
> (In Eupope 'non natural' limes are basicly low strength cement)
>
> 1. Calcic Lime - CL
> Burned limestone with <4% silicium-clay content. Fired at 800-900&#xA1; C
> (It seems that 100% pure limestone does not exist in nature).
> This lime (called 'A?rienne' in France which means 'air') carbonates when
in
> contact with the air and therefore needs to be applied in layers of up to
1 or
> 1.5 cm (very few sources allow 2 cm). A trick of the trade seems to be to
add
> beer (=CO2) to the mix if on is obliged to go more thicly. How this
affects
> quality I cannot say, and I have allways preferred to pour it down my
mouth.
> This type of lime has a very slow curing process. But this is the type of
lime
> that breaths most. Low strength, but flexible (few cracks, moves somewhat
with
> the structure)
>
> 2. Natural Hydraulic Lime - NHL Fired arround 1100&#xA1; C
> > 4% < 20% silicium-clay content
> 'Hydraulic' because it reacts with water, and is in no need for contact
with the
> air. Basicly used for foundations (even those of bridges etc). Its
reaction is
> faster than that of Calcic Lime, it is stronger and less air passes
through it.
> Usually not advised for plastering, unless for fa?ades that receive
excessive
> amounts of rain.
> This (hydraulic) difference is very important as it was discovered by a
> Frenchman (Louis Vicat) in 1913 ;-)
>
> 4-8%  silicium-clay content  NHL 2
> 8-14% silicium-clay content  NHL 3.5
> 14-19% silicium-clay content  NHL 5
>
> * Lime allways has to be extinquished by adding water to the lime. In the
case
> of Calcic Lime (CL) this can be done on site and left to slake. For this
> purpose it needs to be under water in order to avoid contact with the air.
> * Lime should not be allowed to dry before curing (which is a reaction,
not a
> drying process) is well set in as drying disturbs the curing procces. This
is
> most delicate for CL as it has a longer drying p?riod. Soak the support
well
> the day before and several hours before plastering. If needed mist again
just
> before plastering, but take care not to add too much water. Avoid direct
sun,
> too much wind and freezing.
> * Lime can crack when to high a dose of lime or clay is used or when
thickness
> varies
> * Non throweled lime plaster can soak up water and let it pass trhough.
> Throweling closes the poores. A smooth surface makes the water run down.
>
> Then there is cement, Fired arround 1300-1400&#xA1;C
> More or less the same stuff as hydraulic lime, but fired at slightly
higher
> temperatures and an even higer silicium-clay content. >20%
> It reacts in contact with water, it reacts even faster than NHL and is
stronger.
> It lets less air pass through than NHL.
> Also, it is not extinquished as is lime, but rather it is milled to make
it into
> a powder.
>
> To finish it off:
> NHL-Z
> Hydraulic lime that contains (no more than 20%) cement
>
> HL
> Hydraulic lime that is not natural. (basicly blends)
>
> Clay and lime.
> In the old days, lime was mixed with earth, basicly a type of earth that
would
> work well as an earthen plaster or (more commonly) a type of earth that
> contains too litte clay to make it work as a plaster. The clay gives
colour to
> the otherwise white (CL) or grey (NHL) lime plaster. When an earth
contained to
> much clay sand was added.
> But: The clay also has a chemical reaction with the lime or vice versa (?)
> Anyway, the lime destroys the binding properties of the clay. This is why
a
> eathen plaster does not get stronger just by adding a bit of lime. Enough
lime
> needs to be added so that lime wins the struggle.
>
> How to determine how much lime to use (on clean or unwashed sand):
> Take 2 buckets and fill them both to the same level.
> One with the sand, on with water.
> Pour the water on the sand until the water reaches the level of the sand
> Wait 1 hour, add water if it has 'sunken'
> Calculate how much water was added to the sand, relative to volume of
sand.
>
> Others suggest:
> 1st  layer (like a thick soup) 5 vol. Lime for 10 Sand
> 2nd layer 4 lime - 10 sand
> 3rd layer 3 lime - 10 sand
> This is supposed to avoid having cracks one over the other
>
> Pascal Th?paut (who works as a proffesional SB builder in France) uses:
> 1 lime (straight out of the bag) for 3 sand
> First layer : 50% Hydraulic lime (NHL)  50 % Calcic lime (CL)
> Second and third layer only Calcic lime (CL)
> The hydraulic lime makes the plaster set more quicly so the second layer
can be
> applied soon.
>
> Lime is wonderful, Earth is a miracle !
>
> Plaster on,
> Andr?
>
>
> Selon Chris Magwood TLSEditor@...:
>
> > Martin,
> >
> > I was always under the impression that lime was built up in thinner
> > layers because of the need for the lime plaster to recombine with
> > atmospheric CO2. If it goes on too thickly, not only will it crack
> > because of it's own weight sliding down the wall before it sets, but
> > it won't cure fully because the stuff that's buried deep won't
> > carbonize properly. But somebody with more lime knowledge might be
> > able to shed more light on this subject!
> >
> > I think what the testing at Queen's suggests is that regardless of
> > the kind of plaster or its final compressive strength, the thicker it
> > goes on, the stronger the final wall assembly. This is not surprising
> > in itself, but what surprised me was that the thickness made so much
> > more difference than the plaster strength. Better to have 30mm of
> > quite weak plaster than 10mm of super strong stuff. I think it helps
> > make the case for earthen plasters, which like to be thick and don't
> > cost a lot to make thick, and who cares if they're not quite as
> > strong as a cement-based plaster.
> >
> > Chris
> >
> > >Hi,
> > >
> > >for lime one layer should not exceed more than 10 mm due to moisture
> > >protection, so building up thickness traditionally is done in layers
> > >(normally 3). Does this team is confirming this tradition?
> > >
> > >Martin
> > --
> >
> >
> > ***************************
> >
> > Chris Magwood / Camel's Back Straw Bale Construction
> > <a  target="_blank" href="http://www.strawhomes.ca";>http://www.strawhomes.ca</a>
> >
> > Interested in bale building? Have you subscribed to
> > The Last Straw Journal?
> > You should!
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