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RE: QUERY: Protective Coatings for Concrete Structures

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Bill,

There are many concrete seal materials and vendors.  All of them make
promises that fall far short of what they can deliver.  Obviously the old
coating needs to be removed, and the concrete repaired.  Assuming that there
are active cracks, you could opt for a route and seal of the cracks and a
penetrating sealer on the rest of the concrete.  The penetrating sealers are
in the silane and siloxane category.  Use Rilem Tube testing and core to
confirm penetration.  The crack sealer should be a polyurethane.  Make sure
that there is a bond breaker at the bottom or the caulking will fail.

The coating that is currently on the structure sounds like a membrane type.
There are many membrane sealers on the market that will bridge active
cracks.  There are polyurea type of membranes and there are the more
traditional urethane membranes that can be traffic bearing.  The key is in
the preparation and the application.  Make sure you require adhesion
testing.  There are rather extensive tests on membranes and sealers that
have been conducted by the Canadians.  I haven't checked recently but you
might want to search:
http://www.nrc.ca/irc/irccontents.html 
or
http://www.tu.gov.ab.ca/CM/Source/Views/Menu/InternetView.asp?OpenCN=|253|&A
DsPath=/cn=1/cn=24#253

You might also check Sika.  I like their warrenties, and they train
applicators.

Regards,
Harold O. Sprague


> -----Original Message-----
> From:	Bill Polhemus [SMTP:bill(--nospam--at)polhemus.cc]
> Sent:	Monday, March 26, 2001 11:22 PM
> To:	Seaint@Seaint. Org
> Subject:	QUERY: Protective Coatings for Concrete Structures
> 
> Okay, I need some opinions.
> 
> I've got an old (ca. 1964) "folded plate" concrete structure, not
> posttensioned, just formed, reinforced with mild steel and poured in
> place.
> The thing is a pavilion at a city park, circular in plan, with this weird
> "scalloped" roof that varies between about 6" thick at the radially-placed
> bents to about 3-1/2" at the midpoint between the bents.
> 
> It looks like it did have some sort of "rubberized" coating system applied
> at one time, but that has just about gone away, at least on the top
> surface.
> There are some leaks beginning to form, some spalls on the underside. I
> think the thing needs to be cleaned up (get all the old coating junk off
> of
> it) and recoated, but I'm not sure what sort of system would be
> appropriate.
> 
> Do any of you have experience with weather-proofing of large concrete
> surfaces of this type? Any pointers in that direction would be most
> appreciated.
> 
> William L. Polhemus, Jr., P.E.
> Polhemus Engineering Company
> Katy, Texas
>