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RE: QUERY: Protective Coatings for Concrete Structures

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Cementitous products in general are superior for many applications unless
you have active cracks.  Most concrete structures that have problems have
active cracks.  If you seal them up they open up either at the same location
or close by.  Flexible sealants are the appropriate sealant for active
cracks.  Flexible sealants will need to be replaced at some time in the
future.  The polyurethanes appear to have long life, UV resistance, good
elastomeric properties, and good bonding properties if installed correctly.

Inspect the application, test the bond to the substrate by cutting out
sections of sealant.  Get a good fall protection harness, and inspect the
hard to get at places more thoroughly.  I have had to have entire 22 story
buildings totally redone.  It almost bankrupted the contractor, but the job
was done correctly.

In the US we don't take the proper design steps to accommodate thermal
cracking.  I was very impressed by the details and jointing that appears to
be the German practice for cast in place concrete.

There are many good resources for repair of concrete.  Some of the superior
vendors are Sika and Fosroc.  I am moving my office to another floor or I
would have more references for you.  In the mean time check out the
following sites for repair materials:
The repair materials data base at:

I would also recommend the book Chrest, Anthony P.; Mary S. Smith and Sam
Bhuyan. Parking structures: planning, design, construction, maintenance, and
repair. New York: Van Nostrand Reinhold.
And their employer:

For coatings don't use the epoxies unless they are stabilized for UV.  I
would be inclined to go with a poyurethane.  You also need to have a high
perm rate to allow water vapor out of the substrate:

This is what was done on Deer Island in Boston:

Harold O. Sprague

> -----Original Message-----
> From:	Bill Polhemus [SMTP:bill(--nospam--at)]
> Sent:	Tuesday, March 27, 2001 8:56 AM
> To:	seaint(--nospam--at)
> Subject:	RE: QUERY: Protective Coatings for Concrete Structures
> I had planned on removing, patching, crack-sealing, and all just as you
> mentioned. However, I'm intrigued by the notion put forth by Five Star,
> that
> their cementitious waterproofing and dampproofing products are "superior"
> to
> so-called flexible sealants.
> What's your take on that?
> William L. Polhemus, Jr., P.E.
> Polhemus Engineering Company
> Katy, Texas
> -----Original Message-----
> From: Sprague, Harold O. [mailto:SpragueHO(--nospam--at)]
> Sent: Tuesday, March 27, 2001 8:00 AM
> To: 'seaint(--nospam--at)'
> Subject: RE: QUERY: Protective Coatings for Concrete Structures
> 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:
> or
> &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)]
> > 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
> >