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Introduction
When it comes to applying tricks of the trade, the
Oklahoma City Zoo job required quite a few tricks.
The original epoxy coating applied to the concrete
walls and floor of the Oklahoma City Zoo Sea Lion
attraction lasted more than 12 years. The coating
experienced some of the typical problems associated
with epoxy coatings: poor color stability and low
tolerance for movement of the substrate. The show
tank is surrounded by several thousand people seated in
the surrounding stadium in full view of the Sea Lion
show, which is performed several times daily. It was of
utmost importance to have a durable, UV-stable,
cosmetically-pleasing coating applied that would seal
water leaks, provide an elastomeric coating that would
move with the thermal cycling of the concrete and have
the chemical resistance to withstand the saltwater and
chlorine mixture typically used by aquariums.
The Specification Process
On several occasions, technical representatives from
the manufacturer met with maintenance personnel
of the zoo to discuss application procedure,
possibilities, and limitations. The coating system
specified was as follows:
- Poxy Prime H20 (Epoxy) 5 mils dft
- ElastoGard ARC (Polyurea) 60 mils dft
- Polyspar HP (Polyaspartic) 10 mils dft
- Total Coating System 75 mils dft
The Poxyprime H20 primer can be applied using a
roller or airless paint sprayer. The ElastoGard ARC was
applied using a Glas-Craft MX2 plural component
machine at 160F and 2000 psi. The Polyspar HP can
be applied using a roller or an airless paint sprayer.
Preparation and Rehabilitation
of the Concrete
Media-blasting was used to remove the epoxy and
prepare the concrete substrate. On several occasions,
the “blown-out” concrete around the corroded rebar
required removal and treatment of the corroded rebar.
The concrete was replaced with a fast-setting polymer modified concrete. The rebar was treated with a rust
preventative epoxy. After media-blasting, all concrete
surfaces were treated with a chloride-removing liquid.
This liquid was high-pressure washed clean and
priming began. As with all media-blasting procedures,
the entire area was contained and properly ventilated
for the safety of the animals and workers.
Project Challenges
The stadium tank has viewing windows along the
inside of the tank. These windows were a constant
source of water infiltration into the dining room. It was
decided to treat these windows as a picture frame and
simply spray onto the glass and the
concrete in a way that would seal the
leaks…forever. One drawback was that
removal of these windows would require
cutting into the coating. The zoo
maintenance staff did not anticipate
window removal in the near future.
Applying the Coating
System
It is preferable to apply the specified
coating system on a tank-by-tank basis.
This allows the coating to achieve
maximum intercoat adhesion. This
method is also preferable in order to
contain the overspray and blast media.
Final Thoughts
The system specified has shown outstanding
performance in several large applications,
including the infamous San Mateo Bridge
Project. The aliphatic chemical backbone of the
polyaspartic ester provides excellent moisture
permeation resistance, as well as UV-stability.
Chemical resistance tests have yielded favorable
results with chlorine and salt-water. The aromatic
portion of the polyurea provides the elastomeric
nature of the entire system, as well as the
waterproofing portion of the system.
We extend a special thanks to Tim Sanderson of
Evans Industrial Coatings (contractor on this job)
for the pictures and all his hard work on the project.
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