Ilene,
Most of my work is done from a distance anyway and it'd be great to work on
a project with you someday. But as I've said, I'm always happy to sneak in
a little pro bono document review on the side. If you get those submittals
from SpecMix feel free to send them along and I'll give them the once over.
I don't think I know John Zarzecki but if he's distinguishing natural
cements from portland cements and limes then he must be doing his
petrography. If he's submitting his microphotos in his reports then I'm
sure you're getting a good analysis. Next time you speak to him let him
know that I'd be interested in speaking with him.
One additional word of warning on modern matching of early portland-lime
mixes. Remember that the strength, elasticity, and permeability of early
portland may be quite different than the portlands of today as these are
engineered for the demands of high performance concrete construction. A
cubic foot of modern portland may be nothing like a cubic foot of 1913
portland.
Finally, while I am obviously biased, I have to disagree that there is a
time and season for a mortar analysis. For several hundred dollars on one
well chosen sample you can qualitatively identify binders, pozzolans, and
sand with at least an approximate estimate of proportions. My feeling is
that while this might not be a sufficient level of documentation on
moderate-sized projects, it at the very least establishes some baseline to
judge safe preservation practices on even the smallest project. Okay, I'll
shut-up now before I start sounding like a snake oil salesman!
John
-----Original Message-----
From: plz practice conservation of histo presto eye blinks
[mailto:[log in to unmask]] On Behalf Of Ilene R. Tyler
Sent: Sunday, January 13, 2008 1:32 PM
To: [log in to unmask]
Subject: [BP] Spec Mix
Wow! Thank you very much.
I told Brad Hawkins from Spec Mix that he needs to be talking to the design
and engineering professions, if he wants to compete and be listed in
specifications. I want to use local suppliers, and our local contractors
are very open to this supplier, and Brad assured me they use local sources
of cement and sand. I love your products, Michael, but I'm keeping an open
mind for local sources. I respect the response from all of you, and told
Brad that I needed some kind of peer response, but didn't tell him about our
little secret listserv.
Meanwhile, I will request more data on the mix. This project doesn't
require a technical match to original mortar, but the building dates from
1913, so there is the possibility they used a lime-cement mix. Still, I am
comfortable going with our contractor's recommendation, and keeping on
schedule.
My local material scientist and lab consultant is John Zarzecki, with SME,
who has been a great help for mortar testing and explanations, but he has
some issues with Spec Mix. If you were closer, John, I'd love to have your
expertise on a job. You and Michael really understand natural cements.
Ironically, John Zarzecki found evidence of natural cements for an 1880s
church project up north, but only for a study, so doubtful we'll get to see
this through specifications and repairs. We rarely encounter this in SE
Michigan, but the church imported their brick from Wisconsin, and apparently
they got cement from there, too. The mortar analysis was an interesting
piece of the study, which we wouldn't have discovered if we hadn't done the
analysis. For every mortar analysis, there is a season, and a time, etc....
Again, thank you, all.
Ilene R. Tyler, FAIA
QUINN EVANS | ARCHITECTS
219 1/2 N. Main Street
Ann Arbor, MI 48104
ph: 734 663-5888
fx: 734 663-5044
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