Concrete Prep
Preparation of Concrete
Surface Preparation | 800.808.0414 |
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Preparation of Concrete
Surface Preparation
Preparation of Concrete
Coating performance is directly affected by surface
preparation. Integrity and service life will be reduced
signicantly if the surface is improperly prepared. Selection
and implementation of the proper surface preparation
ensures coating adhesion to the substrate and prolongs
the life of the coating system. New concrete must be cured
prior to coating. “Cured” is generally dened as, “concrete
poured and aged at a suitable temperature for at least 28
Examine the Surface
Prior to planning a job the contractor should survey of the
concrete surface. If excessive laitance is present, this material
must be removed down to solid concrete. The coating or
overlay will not bond properly to the weak layer of concrete.
The surface should be checked for barriers such as existing
sealers, curing materials, grease, oil, eforescence, and dirt
that must be removed. In short, you want no surprises.
Test the Concrete
A “water drop” test can be used to determine if the surface
is clean. Water beads on surfaces contaminated with sealers,
curing compounds, oil, and grease. Water beads on surfaces
that are too dense to accept a penetrating primer.
Clean Uncoated Concrete
Remove any chemicals, oil, and grease from the
concrete first.
Repair Surface Defects
Grind or chip off from the concrete surface all projections
greater than 1/16”. Remove any loose concrete, then clean
and ll holes, cracks and other surface defects with an
approved method. Determine if the patch surface texture
should be rough or smooth, and how long the patch needs
to cure before being coated.
Previously Painted Surfaces
Examine the existing coating to ensure that it is well bonded
to the concrete. Any loose coating must be completely
removed. Edges should be sanded to a feathered edge.
Clean the entire oor thoroughly with detergent cleaner. The
surface must be free of all dirt, oils, or other contaminants.
After the oor has completely dried, sand the existing coating
until a powdery residue is evident and all gloss is removed.
Sweep or vacuum clean, and wipe with xylene to ensure
good adhesion of the new system. When coating over existing
coatings, a test patch is always recommended to
evaluate compatibility. Moisture Vapor Transmission (MVT)
Moisture Vapor Transmission (MVT), also referred to as
“hydrostatic pressure”, “capillarity” or “vapor pressure”, is caused by
moisture being present underneath the concrete slab. MVT can cause
blisters, bubbles and other effects in a resinous coating. As moisture
rises, it dissolves salts in the concrete and becomes alkaline. This
alkaline water attacks the resin. Damage caused by MVT does not
constitute product failure. We recommend that contractors include a
written MVT disclaimer in all of their contracts before beginning a job.
We also recommend that contractors always test for signs of MVT
problems. This will not ensure that the problem may never
occur. If a problem is suspected, contact your
FlexRockCoatings Representative to discuss preventative
All slabs should be tested for MVT. In slabs that exceed the maximum
test results contact your FlexRockCoatings Representative for
Acceptable Test Methods for MVT
Calcium Chloride Test: Perform a quantitative
anhydrous calcium chloride test in accordance with ASTM-
F1869 Standard. The maximum acceptable result for this test
method is 3 pounds per 1,000 sf per 24 hours.
Relative Humidity Test: Perform a quantitative Relative Humidity
test in accordance with ASTM F2170 Standard. The
maximum acceptable result for this test method is 75%.
Concrete Preparation Methods
Once a common practice, acid etching is no longer an
approved method of concrete surface preparation.
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Preparation of Concrete
Shot Blasting
Steel shot blasting involves steel shot being centrifugally propelled at
high velocity onto the surface. This process is confined in an enclosed
blast chamber that recovers and separates dust and reusable shot.
Shot blasting is principally used to roughen horizontal surfaces
in preparation for the application of sealers, coatings, or polymer
overlays. This method is also used to remove polyurethane coatings
up to 10 mils thick, tile mastics, and brittle coatings such as epoxy or
methyl methacrylate systems up to 1/8 inch thick. Removal of thicker
materials may require multiple passes. Shot blast systems produce
very little airborne dust or contamination. Most models can be fitted
with a filter to further lower the level of airborne dust produced.
Diamond Grinding
Diamond grinding is the rotation of one or more abrading stones
or discs applied under pressure at right angles to the surface. This
method may be used on horizontal surfaces to remove deposits or
coatings, and to reduce or smooth surface profile. The grinding stone
or disc is applied under pressure and moved across the surface until
the desired effect is achieved Diamond Grinders can utilize both
metal or resin bond diamonds that can be used either wet or dry for
concrete grinding. Solid carbide scarifying cutters are used for thicker
coatings. Grinders can also be used effectively to level uneven
joints or high spots of 1/16 to 1/8 inch. Grinding provides
contractors with a smoother nish than shot blasting, scariers
or scabblers.
Scarifying is the rotary action of the cutters (toothed
washers) impacting the surface at a right angle to fracture
or pulverized the top surface of the concrete to expose a
clean, fresh surface. The cutters are assembled on tempered
steel rods mounted at the perimeter of a drum that rotates at
high speeds. Scarication is used for the removal of concrete
or coatings up to 1/4 inch thick. It may also be used to prole
concrete surfaces. Scarication can also cut deep grooves
into the concrete to provide a non-slip surface.
Scabblers use compressed air to hammer piston-mounted bits
into the concrete surface, roughening the concrete surface
more than grinding or scarifying. Scabblers can remove up to
1/4 inch of concrete surface in a single pass. Scabblers are
ideal for removing spalling concrete, removing epoxy, and
removing loose or deteriorated concrete.
Please read all safety data before using product.
DISCLAIMER: All statements and recommendations are
based on experience we believe to be reliable. The use or
application of these products being beyond the control
of the Seller or the Manufacturer, neither the Seller nor the
Manufacturer make any warranty expressed or implied, as to
results or hazard from its use. The suitability, risk and liability of
a product for any intended use shall be solely up to the user.
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