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News
Waterproofing
Waterproofing is the process of treating an otherwise porous
surface to prevent the migration of water (or other liquids) through the
substrate directly or through seams. This process is best accomplished on
the positive side of the substrate: the side receiving the initial
exposure. This discussion will focus on waterproofing of flooring
applications such as parking decks, mechanical equipment rooms, balconies
and pedestrian decks.
It is important to apply waterproofing systems to prevent the corrosion
and deterioration of concrete in conditions exposed to continuous weather
conditions. Indoor applications utilize waterproofing whenever there is a
chance that water will have the opportunity to migrate to a lower floor.
These cases may include pool areas, showers, mechanical equipment rooms
and utility rooms.
Although concrete is the most widely utilized construction substrate,
it does have limitations with respect to heavy wear conditions and its
inherent porosity. In addition, concrete shrinks during its curing process
and will expand and contract through seasonal temperature changes. For
this reason, joints are constructed in the concrete to address initial
shrinkage as well as continuous movement. Cracks in concrete are unplanned
“natural” joints. When an area requires waterproofing it is these details
which require a membrane waterproofing technique rather than a simple damp
proofing penetrating treatment.
Membrane waterproofing systems are designed to provide a flexible
watertight coating bonded directly to the substrate (frequently with the
use of a primer). In order to protect this membrane as well as provide a
slip resistant wear surface, one or more applications covers the membrane
providing texture, durability, chemical and/or UV resistance. The
chemistry of these membranes has evolved rapidly over the course of the
last forty years. Initial seamless technology utilized latex chemistry
which is flexible and non permeable.
The development of polyurethane elastomers improved upon the
performance of waterproofing membranes and became the most widely utilized
material for most exterior applications. Polyurethane elastomers can be
constructed to be lights stable (Aliphatic versus Aromatic) and can vary
in solvent content. Polyurethane elastomers have excellent elongation but
bond strength to concrete is lower than internal tensile strength which
permits a system to disbond from the substrate. Although this situation is
advantageous over a moving crack, it becomes a problem in traffic
situations if the membrane is compromised resulting in an undercutting of
the system which is difficult to stop and repair. This relatively low
adhesive strength of polyurethane systems requires the wear course layers
to be constructed to accommodate the inability of the system to hold
aggregate throughout its service life in high traffic areas.
Flexible epoxies were developed to address the limitations of
polyurethanes. EPO-FLEX was the first of these products to be
commercialized in the United States. It is 100% solids (no solvents), has
low odor, and bonds tenaciously to the substrate and to the aggregate when
used in a wear course. Although flexibilized epoxy materials are
inherently more expensive than polyurethane elastomers. These systems are
competitive because they require less material as sacrificial wear coats
in heavy traffic areas. These systems have also been designed using stress
relieving epoxy wear surfaces in situations not expected to experience a
great deal of movement. Both epoxy and polyurethane systems are limited by
the environmental conditions during installation. The temperatures must be
greater than 50 F and humidity and dew point can affect both cure and
adhesion.
The newest chemistry available for waterproofing is Polyurea. This
technology was originally developed for injection molding due to its cure
speed but modification has allowed its use as a spray applied membrane
system. It has excellent flexibility, good adhesion when used with a
primer, excellent abrasion resistance and most importantly cures in
minutes at temperatures as low as -30 F. Cold temperature application may
be most advantageous if the system requires off-season cold temperature
repairs or additions. True Polyurea products, such as General Polymers’ EnviroLastic,
unlike polyurethane or hybrids, are not adversely affected by moisture
during application. By varying the material and the spray technique an
aggressive surface can be applied over a parking deck Polyurea membrane
which provides long term wear, slip resistant texture and a surface that
can be easily cleaned.
Parking decks
Regardless of the system or chemistry selected for parking deck
service, there are some common characteristics which must be addressed.
These include:
As with parking decks, these systems must provide waterproofing but
they do not experience the degree to abrasion and traffic conditions. In
some cases these systems will utilize a simple smooth topcoat or a
decorative finish. Movement in MER’s is substantially less than Parking
structures but water exposure must be contained or pitched to a drain
requiring cove base and drain details. Because MER’s are indoors, it
becomes more important to utilize a low odor system. In some cases, it
will be necessary to use 100% solids, no volatile organic solvents system
to prevent fire hazards from water heaters or furnaces.
Systems Supplied by General Polymers
In these pedestrian deck applications, there are commonalities between
MER traffic conditions and exterior weather conditions as experienced in
parking decks. Pedestrian deck applications must withstand structural
movement due to seasonal changes, handle light foot traffic, have an
aesthetically pleasing appearance, be easy to clean and resist degradation
by sunlight exposure.
Systems Supplied by General Polymers
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