Message text written by "BP - \"where heavy conservationists hang out\""
>My only question is, does Jahn shrink 11% or 11/100 of 1%.  Would seem to
me
that the .11% you wrote, Mike, is pretty negligible.  But if that's too
much,
it's too much--but is it too much?  How does the Jahn shrinkage compare
with
the Edison-lauded concrete repair products?  The structural engineers,
whose
practice is (almost) limited to repair work, for whom I work have high
regard
for Sika conc repair material.  What say you, Mike?

Ralph
<

11% would be truly exceptional high shrinkage-- the ICRI Guideline defines
high shrinkage as >0.10% and states that based on field experience high
shrinkage can lead to significant problems. Though this number may seem
small, you have to consider that these materials get placed in large
volumes sometimes, and when you take this sort of shrinkage over a larger
volume you're almost guaranteeing crack development. While some engineers
are not concerned about cracking because they are accustomed to seeing it
in perfectly serviceable concrete, it is at the very least unsightly and,
after all, these are supposed to be Aesthetic repairs. I happen to be of
the persuasion that a cracked patch IS a failing patch, because cracks of
only 0.008 inches in width will leak, and as we all know, water
infiltration is the primary driving mechanism in deterioration.

Shrinkage data I have seen for Edison Custom System 45 patching compounds
is on the order of 0.04% ("Low") to 0.06% ("Moderate"). The ICRI guideline
describes moderate shrinkage as 0.05% to 0.1% and low shrinkage is less
than 0.5%. There is also a "very low" shrinkage category, but there can be
a whole different set of problems with products in this category.

Sika and Master Builders are two manufacturers whose products have been
very effectively marketed and supported for the engineering community,
among others. These are usually designed to be structural repair materials,
and are not used in aesthetic repair unless the scope of work also includes
a paint job.

Mike Edison