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RE: Protective Coatings on Precast Concrete

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Nick, 

You have already found the major issues.  Other issues are:
1.  Silanes / Siloxanes
1.1  Testing - Use a Rilem tube to see if it was coated correctly
1.2  Masking - Glass and metals need to be protected during the application.
The liquid applied masks must be removed prior to a specified time, or they
will be very difficult to remove.
1.3  Longevity - You have already discovered that it will have to be
reapplied in a very short time frame.  

2.  Elastomeric coatings
2.1  These materials will not have a high perm rate, and will prevent
trapped moisture.  This will result in blistering and repairs until the
moisture has been allowed to escape.

You may want to also consider cementitous coatings.  There is an article in
the current Concrete Repair Bulletin on concrete coating analysis.  Check
out their web site: http://www.icri.org/

Another organization that may be of help is the Sealant, Waterproofing, &
Restoration Inst. http://www.swrionline.org/

There are also masonry coatings that have a good perm rate that you may want
to consider, but you are asking a lot in regard to longevity.

Check out the US Army Corps of Engineers "High Performance Coatings":
http://www.cecer.army.mil/td/tips/product/details.cfm?ID=568&TOP=1

Or go to the USACE Paint Technology Center: 
http://www.cecer.army.mil/pl/project/index.cfm?RESETSITE=Project-PaintLab

Here is another web site for the protective coatings:
http://www.protectivecoatings.com/

Some other resources: 
Tnemec http://www.tnemec.com/
Ameron: http://www.ameroncoatings.com/www/
Prosoco: http://www.prosoco.com/

Regards,
Harold O. Sprague

> -----Original Message-----
> From:	npitera(--nospam--at)mmm.com [SMTP:npitera(--nospam--at)mmm.com]
> Sent:	Friday, October 04, 2002 9:38 AM
> To:	seaint(--nospam--at)seaint.org
> Subject:	Protective Coatings on Precast Concrete
> 
> I looking at a  multi story office building that has exposed aggregate
> precast
> concrete  load bearing wall panels. You know, that Soviet concrete look
> that was
> the rage in the late 60s- early 70s. Over 90 % of the wall panels have
> cracks,
> multiple cracks. We took some core samples to the lab for analysis. The
> concrete
> is not air entrained, and the microcracking is attributed to water
> absorption/
> freeze -thaw cycling.
> 
> In order to solve the problem long term, I'm looking at coatings/sealers.
> Your
> typical Silane/Siloxane sealers I'm finding out are only good for 3-5
> years,
> which on this building would be considered a high maintenance issue, and
> it
> really won't bridge cracks very well. Then there are your elasticmeric
> coatings
> which as I understand can let the building breath but are only good for
> about 10
> years. Considering all the prep work and cost required, even ten years is
> not
> enough.
> 
> Has anybody had any good, bad, or ugly experiences with elasticmeric
> coatings or
> sealers?
> Any comments on this matter will be greatly appreciated.
> 
> Regards,
> 
> Nick
> 

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