Michael,  You say "We have been preparing cement-lime custom
     mixtures...". Who is "we"? How does one go about asking the "we" for a
     particular mixture to match an historic mortar? I'm thinking that
     historic mortars are what you are talking about. Of course, I could be
     as wrong as three left feet.

     Also, I have to be concerned that the latex additive moisture release
     tests were at near-saturation. I would not want my mortar to have to
     go to near-saturation before the moisture was released. That would
     permit too much moisture to stay to the inside of the building and not
     escape as it should, when it should. This would cause build-up of
     molds and fungi and all sorts of pathogens, not a pleasant thought.
     -Grace


______________________________ Reply Separator _________________________________
Subject: Re: Latex Additives
Author:  "michael p. edison" <[log in to unmask]> at internet
Date:    8/15/98 12:19 AM


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.