Decorative Concrete & Resurfacing Options
-Integral Colored Concrete
Stenciling Patterns Into Concrete:
-Stenciling On Fresh Poured Concrete
Walls - Stone-Crete
what you're working with - both internally and externally is
a key to successfully preparing a concrete surface for accepting
cementitious toppings. A slab may look clean and sound, but that
doesn't necessarily mean it is. Your system will only be as good
as the surface underneath. Below are a few steps to ensure proper
with a walk - Depending on its condition, every concrete
surface requires some preparation to create a proper texture,
for applying coatings. A visual evaluation is the first step.
Walking the floor to carefully note differences in surface
cleanliness, grade and condition is a must. Look for any existing
sealers, grease, oil, effervescence, curing materials and dirt
that need to be removed. Excessive laitance or a weak layer
of cement on the surface must be removed down to solid concrete.
Coatings and overlays will simply not bond properly to weak
concrete. A few tests can help gauge the slab's structural
integrity. Take a screwdriver or nail, and pry up test areas
of the surface that appear loose or soft. Strike a ball peen
hammer against the concrete surface to indicate hardness. Hollow
spots can be determined by sweeping a surface with a metal
chain or golf club and listening for pitch changes.
moisture and vapor transmission - Moisture is a huge problem
when it comes to surface preparation. Moisture can basically do three
things to concrete:
it can hurt the concrete itself when the alkalinity reacts with the
aggregate; it can destroy certain polymers; and it can expand to remove
toppings from the surface. Excessive vapor transmission occurs when
a water source under the slab is combined with concrete that is usually
permeable. That source could be a high water table, broken water pipe,
landscape sprinkler or rain. Overly permeable concrete usually results
from a water-cement ratio that is too high. The excess water leaves
the slab, during the curing process and creates capillaries that serve
as a pathway for water vapor to be drawn up through the slab. The most
cost-effective method of determining if moisture vapor is passing through
the slab is the calcium chloride test. To solve this problem, applying
a waterproof product that penetrates the concrete to form a permanent
gel-like barrier, which can never be worn away. In one application,
the product holds the hydrates in, thus waterproofing the concrete
internally as well as externally.
Repairing the cracks - All concrete surfaces crack. It
is important to repair
cracks because, if left, they will spread and cause concrete to
become unstable. Coatings, too, will fracture along joints or cracks
that are not properly addressed. The key in making repairs is to
determine the kind of crack you're dealing with. A cosmetic crack,
which does not go all the way through the slab, will be addressed
differently than a structural one. Cosmetic cracks are the easiest
to handle - cut the crack and seal it with a hard filler material.
Structural cracks are more difficult. Most often, you should square
cut the crack, and then apply a flexible epoxy resin or sealer.
Most cracks that occur in the slab are not moving cracks, but some
do move or vary in size because of seasonal differences in temperature,
moisture levels, stress loads and other factors. You should design
your system to honor the cracks, to allow the floor to move.
4) Cleaning the
surface - Once you've got a handle on the slab's character and
have repaired and solved any problems, the next step is to clean and
condition it thoroughly. To ensure a bond between the topping and the
concrete, the slab must be absolutely free of dust, dirt, oil, grease,
paint, curing components, coatings and all other contaminants. To determine
if the surface is clean use the water drop test by applying a small
amount of water onto the floor. If the water doesn't penetrate into
the pores, neither will a coating. Cleaning a slab may be as simple
as scrubbing the surface with an aggressive nylogrit brush and then
applying commercial cleaners. The surface can then be rinsed with a
pressure washer and allowed to dry. Pressure wash works well for chemicals
and oils. Degreasers worked in with a floor scrubber/polishing machine
can adequately remove dirt and grime. Detergents and cleaners can also
be effective as long as the grease and contaminants are water soluble
or emulsifiable by the detergent or cleaner. They work best for removing
superficial grease, although more than one treatment is often necessary.
High levels of contaminants may require grinding.
Knowing what you're removing - Removing previous coatings
products depends on the type and nature of the material to be
removed. For thin sealers, concrete grinders or brush blasting
with a shot blaster are appropriate. For epoxy, mastic and thick
coatings, concrete grinders with aggressive cup wheels or scarifiers
can be used. Machines with carbide-tipped slicers can quickly
remove thick coatings. Hand-held or ride-on floors scarpers can
effectively remove such materials as carpet, parquet flooring
and other thick materials. If the surface is delaminated, shot
blasting, scarifying or other chipping methods must be used.
Shot blasting works well as long as the material is not rubbery.
Muriatic acid can be used to clean and profile concrete surfaces.
Through advances in technology muriatic acid is also offered
in a gel. This gel keeps the acid on top of the slab where the
profiling is obviously needed.
Creating a surface profile - Creating a profile is an essential
in the job's eventual outcome. It's one of the keys to getting
cementitious topping to bond. Profiling the surface mechanically
includes grinding, sandblasting, shot blasting and using other
tools. Chemical profiling includes acid washing, chlorine washing
and other chemical methods to remove surface imperfections. The
preferred method for large or difficult surfaces is mechanically
profiling. Shot blasting is one of the most popular and cost-effective
methods of creating a profile, and it is most suitable for 1/8-inch
or thicker toppings. Scarifying can resurface horizontal surfaces
and smooth faulted joints, and cut deep into the concrete to create
non-slip surfaces. Grinding creates less of a profile but it's
often used for edges.
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