[Strawbale] FW: Hydraulic vs. Hydrated Lime

[Andrew deGruchy]

Dear Lime Lubbers/Strawbalers and the like,

Sorry I have not gotten back to these and many other questions. A Hi-Cal
Low-temp burned Type S hydrate can be obtained through Mississippi lime
company in the US. As far as how much brick dust to add I refer to this
quote from antiquity for your consideration:

"Monsieur Loriot's Mortar, the method of making which was announced by order
of his Majesty, at Paris, in 1774, is made in the following manner:--Take
one part of brick dust, finely sifted, two parts of fine river sand,
screened, and as much old slaked lime as may be sufficient to form mortar
with water, in the usual method, but so wet as to serve for the slacking of
as much powdered quicklime as amounts to one fourth of the whole quantity of
brick dust and sand.  When the materials are well mixed, employ the
composition quickly, as the least delay may render the application imperfect
or impossible."

However, I think I stand corrected about brick dust, although it is and was
used to accelerate the set, it does not make the hi-cal lime "hydraulic",
meaning to get its set because of the presence of water. For those who need
an equation to be sure, it is understood that a hydraulic set is represented
by:

2(CaO)2 SiO2 + 8,6 H2O	---->	(CaO)3,41 (SiO2)2 (H2O)8 + 0,6 Ca(OH)2
2 C2S	+ 8,6 H		---->  C3,4 - S2  H8 + 0,6 CH

Further, brick dust may increase the strength but decrease the vapor
permeability. Meta kaolin has a high aluminates content and fly ash has a
high alkali content which are both detrimental to building mortars if you
are considering those as Pozzolans. The truth is that unless a lime has a
hydraulic property all on its own and is then part of the mix, whereby type
s hydrate and a pozzolan are also added, the final result is not going to
have a hydraulic set as described in the above formula.

Due to costs, and if you are going to go to all the trouble of finding these
ingredients, you might just consider to go right back to the Masonry cement,
type s hydrate and sand mix we talked about in a previous letter. You will
have a lot of questions regarding brittleness, negative reactions, etc. ,
and I personally consider it a compromise to what is optimal. It is not a
perfect world though and it happens in historic restoration work all the
time. Those attending to the work just call the mix,(with a little Portland
cement in it), "A High-Lime Content Mortar" and they don't mention the "P"
word. If you go back to using Masonry cement it will allow you to stay away
from mentioning the P word too. Although, (P)-ortland cement is actually
what is in Masonry cement along with the crushed limestone filler and other
additives. I don't want to suggest to just close your eyes and say if I
don't see it, then it is not there, but I find that for some reason many
people, for one reason or another, (and cost is a big one), want to find any
way possible to make the "square peg fit into the round hole." My position
is that I don't fight restoration masons, architects or conservators who
keep believing it is OK to continue with this "High Lime" terminology and
the mixes that do contain the material which starts with the letter after
"O" either. I just have come to the place where I have decided what I will
do and I take the NHL route for restoration work and in the final analysis
doing this makes the already hard work of masonry a little more bearable in
my opinion.


So, I would not suggest trying to add brick dust unless you want to set up a
lab to test results over time, unless you are building an outbuilding or
something with a low investment, not a house. Do remember that the brick
dust should be low-temp fired too, (like from recycled historic brick.)

To Miles Eddins I write that the answer about mixes for Foundations could be
NHL 5 and 2 parts well graded sand. Please e-mail me separately on the
specifications for the foundation and I will attempt to design a suitable
mix for you based on other variables we should discuss.

Sincerely,


Andrew L. deGruchy
Owner/Consultant
Lime Works.US
P.O. Box 151
Milford Square, PA 18935
www.limeworks.us
Technical help phone 215-536-6706
e-mail: begreen at limeworks.us

Material Order only:
Attn: Jim Plante
Phone: 215-536-6706
Fax: 215-536-2281
e-mail: order at limeworks.us


-----Original Message-----
From: strawbale-bounces at listserv.repp.org
[mailto:strawbale-bounces at listserv.repp.org]On Behalf Of
Eddymiles at aol.com
Sent: Sunday, March 04, 2007 5:30 PM
To: strawbale at listserv.repp.org
Subject: Re: [Strawbale] Hydraulic vs. Hydrated Lime



Thanks Andrew for the information on hydraulic vs. hydrated lime. It
answered
several of my questions concerning the use of locally available type S lime.
Would you mind commenting on a few more items pertaining to this discussion.

1. What ratio of brick dust : lime would you recommend for a good hydraulic
set and what alternative locally available materials might achieve the same
results as brick dust if it is not available.

2. Can you recommend a lime mortar mix for bedding stones for foundation and
basement walls? It seems the plasticity of lime would be a plus for this
type
of work.

Thanks,

Miles Eddins


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