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Subject:
From:
"Michael P. Edison" <[log in to unmask]>
Reply To:
BP - His DNA is this long.
Date:
Sat, 15 Aug 1998 00:19:31 -0400
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Message text written by "BP - His DNA is this long."
>From: Leland Torrence <[log in to unmask]>
Subject:      Re: Latex Additives
To: [log in to unmask]

Mike,

You mention using latex additives in situations of high moisture exposure,
what about the reverse- moisture release?
I didn't know you were doing the lime thing?  Tell us more?

Best,

Leland<

The influence of latex admixtures on pointing mortar moisture release can't
be dealt with intelligently without going back to my original pint about
polymer:cement ratio. I would expect a diluted latex admixture at, say, .08
polymer:cement ratio to behave very differently from a more concentrated
mixture of 0.2 or more.

My general impression of latex modifier behavior in what you are calling
"moisture release", or negative-side moisture exposure, is that conditions
of subsurface near-saturation are roughly equivalent to continuous
immersion applications. The data I have seen on continuous immersion of
latex modified mortars suggests that the mortar eventually loses the latex
performance enhancements, and properties drop off to those achieved without
latex.

So initially I would expect reduced levels of moisture release, but after
the mortar becomes saturated, it behaves more like an unmodified mortar. In
the immersion tests we have done with latex-modified vs. unmodified
patching mortars, we found the differences in absorption and release of
moisture to be limited to the first few hours of exposure only. This may
have been more related, however, to the higher number of macro-defects
(large bubbles and pores) in the unmodified product tested, rather than a
result of the latex itself.

As for the "lime thing", we have been preparing cement-lime custom mortars
under the "SPEC-JOINT 46" product name for about 10 years, now, and have
produced these in quantities ranging from 50 pounds to 75 tons for projects
throughout the United States. A complete range of cement-lime proportions
is offered, in accordance with the ASTM C270 standard.

Mike E.

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