Thanks to everyone who responded about my mortar problem.
We are somewhat resolved now to keep our original and specified mortar
mix, which I didn't think of as Type K but as a modified Type N. Type K
isn't in the ASTM charts. This is a slow-curing hard mortar, which
should test at 5-700 psi in 7 days and cure to 12-1500 psi at 90 days.
It matches the original design, and we believe this was specified to
allow for all kinds of movement in the face brick of large brick walls
with no expansion joints. It has served the 89 nine year old building
extremely well.
The problem is that it can't be mixed or handled the same as cement or
cement-lime conventional mortars. We have good advice from John
Zarzecki at SME supporting our decision to stay with the design. We are
working with the contractor to make his adjustments and keep to specs.
And, for the record, my husband and I loved "The Fast Runner". Yes,
it's almost 3 hours in Innuit, but it is beautiful. It is a fable of a
lost culture, and the story is beautifully told. Ralph was not fully
prepared for the experience; it helps to know in advance that it is
almost 3 hours long and subtitled. Don't forget to stay for the
credits, too, as they show a bit about how the movie was filmed in the
horrific climate. Anyway, support your local alternative and downtown
historic theaters!
QUINN EVANS | ARCHITECTS
Ilene R. Tyler, FAIA
219 1/2 N. Main Street
Ann Arbor, MI 48104
[log in to unmask]
www.quinnevans.com
v 734.663.5888
f 734.663.5044
Date: Wed, 7 Aug 2002 12:22:15 -0400
From: Ralph Walter <[log in to unmask]>
Subject: Re: Could we sign them up on B-P? Perhaps that would have a...
In a message dated Wed, 7 Aug 2002 11:14:55 AM Eastern Standard Time,
[log in to unmask] writes:
> That figures, the man was bi-polar.
And a bricklayer and painter, too. Does that make him multipolar?
And speaking of polar, and boring, don't ANYBODY ever see a movie called
The Fast Runner. Mrs. Ralph dragged me to it, and why I sat through 3
hours a Eskimo Domestic Disputes is a mystery. And to think I sat on
the same ass that got pinched lo those many years ago. Maybe there
isn't a mystery after all.
Ralph
------------------------------
Date: Wed, 7 Aug 2002 18:51:54 -0400
From: "M. P. Edison" <[log in to unmask]>
Subject: Mortar Strength
I read Mark Clark's message with interest, because:
1. Mea culpa. It makes me realize that I misread the original posting,
which describes a Type K, not Type O mix and 2. It underscores the
confusion in the grey areas surrounding the borderline between all-lime
and cement-lime blends.
It seems to me that Mark approaches the question from the point of view
of someone accustomed to working with pure lime mixes, whereas,
admittedly, our work has almost entirely involved cement-lime blends. We
do millions of pounds of Type N and Type O mortars, smaller and more
infrequent runs of Type K's.
The main reason I am given by conservators for specifying Type K is to
gain early frost and rain resistance, an important consideration in the
Northern states. The curing requirements are also reduced, as are lime
streaking tendencies, which can be of value when engaging commercial
restoration contractors who have not mastered the art of employing more
traditional materials, a commercial reality.
The 3:1 sand to cementitious materials ratio is correct for Type K,
although I would agree with Mark that most all-lime mortar recipes I
have seen use less sand. I disagree with the comments about Type I White
Portland cement, however. White cement is not made white by higher
temperature firing, it is white due to lower iron content in the rock
used as feedstock for the cement plant. Type I White cement must meet
the same performance requirements as Type I grey cement, under ASTM
C150.
What may be confusing to those who rely on feel and observation, rather
than quantitative methods, is that in order to maintain a certain level
of brightness, cement producers often grind their white Portland to a
finer particle size, similar to a Type III grey cement. This produces a
little faster hydration due to increased surface area, but the ultimate
strength is unchanged.
We have used white cement in Type K mortars without any reported
difficulties. While I am inclined to agree that mortars which are too
hard are a potential disaster, I am also inclined to question what
represents "too hard" in many situations. Certainly the age and design
of the building, the hardness of the stone or masonry, and the weather
exposures are important engineering concerns. Sometimes engineering
approaches may point you in opposite directions from typical
preservation philosophies. I tend to encourage the use of critical
analysis as to the true needs of each particluar situation.
Edison Coatings, Inc.
M. P. Edison
President
3 Northwest Drive
Plainville, CT 06062 USA
Phone: (860)747-2220
Fax: (860)747-2280
email: [log in to unmask]
Internet: www.edisoncoatings.com
------------------------------
End of BULLAMANKA-PINHEADS Digest - 7 Aug 2002 to 8 Aug 2002 (#2002-212)
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