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CASTinTACT
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maintenance & protection guide
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The degree of change can be controlled by the type of acid in the
cleaner, its concentrationand the lengthof timeon thepanels. Proprietary
cleaners will give specific instructions on their application. These directions
should be followed. In order to achieve proper results, cleaners should
be tried on a small area to test results and any color changes. The
concentration and time on the panel can be adjusted accordingly.
Protective clothing and goggles should always be worn when using
acidic solutions.
Anticipate where the cleaning fluids will drain, i.e, across the pavement
and not onto grass or vegetation. Sediment or cleaners allowed to
pond in low spots may stain the panels. Be sure to rinse these areas
thoroughly. Turn off all automatic sprinkler systems during cleaning,
sealing and drying.
Professional Cleaning Methods
For most jobs, cleaning should be handled by a professional company
experienced in the use of cleaners and spray equipment. Professionals
typically use a pressure washer. The various methods for applying sealers
are covered later.
A high pressure sprayer applies cleaner and water between 600 and
2,000 psi (4.1 and 13.8 MPa), and at a rate between 6 and 12 gallons/
minute (22 and 45 liters/minute). The rate of flow is adjusted to ensure
sufficient rinsing. The pressure loosens dirt and pushes water from the
surface without the need for scrub brushes. The nozzle type and its
distance from the panels surface influences the effectiveness of the
cleaning as well. A nozzle that creates a wide spray enables a large
area to be covered efficiently.
Cleaners to remove efflorescence are applied with a low pressure pump
spray under 30 psi (0.2 to 0.7 MPa). A shower type spray nozzle will help
ensure even distribution of the cleaner. Cleaning chemicals are applied,
allowed to sit an appropriate time, then rinsed away with a high pressure
sprayer. The final rinse should be water only.
For small areas, an adequate cleaning job can be achieved without this
equipment. Cleaners can be applied by hand, the panels scrubbed to
remove dirt and efflorescence, then thoroughly rinsed with water from
a garden hose. Scrub brushes with steel bristles are not recommended.
They will loosen from the brush, rust, and leave stains. Brass or plastic
bristles are acceptable.
The additional time required to clean and seal panels without the help
of a professional should be weighed against investing in a competent
company to do the job. Professionals have the equipment and
experience with the various chemicals. They can achieve the highest
level of results in the least amount of time.
What Is Efflorescence?
Efflorescence is a white powdery deposit or milky filmwhich can appear
on the surface of concrete as water evaporates. Efflorescence occurs
with all concrete and is most noticeable with colored concrete. It is
generally accepted that the addition of inorganic color pigments does
not enhance or retard the occurrence. Efflorescence is caused when
soluble salts and other water dispersible materials migrate upward to the
surface of concrete. This is caused by the sun evaporating the moisture
on the surface. This capillary wicking action continues to draw moisture
from within until the moisture is exhausted. Efflorescence is enhanced
by low temperatures andmoist conditions; condensation, rain, and dew.
If concrete placement happens during a dry period of the year, the next
cycle of colder, wet weather may trigger the efflorescence to occur.
Efflorescence will continue until all the salts have been exhausted. It
may remain for months and some of it may wear away. In no way does
it affect the structural integrity of the concrete.
Any concrete product containing portland cement can produce
efflorescence. Calcium hydroxide (free lime) a by-product is produced
in the hydration process of portland cement with water (approximately
140 pounds per cubic yard of concrete). During this reaction period,
the excess water mixture, a calcium hydroxide solution migrates through
capillaries in the concrete to the surface where it evaporates. There
it combines with carbon dioxide from the air to produce calcium
carbonate (insoluble salt). Only 0.2 ounce of calcium carbonate per
square yard of surface area is needed to cause a significant change
in color. In colder temperatures calcium hydroxide is actually more
soluble to migrate to the surface. Efflorescence can also be caused
by sulfates of either sodium or potassium that are more soluble in water
than calcium and can easily be rinsed away. These type of salts can
come from cement, aggregates, water, or admixtures.
Removing Efflorescence
Powdery Efflorescence
The recommended procedure is to allow the natural process to occur.
Powdery efflorescence can often be removed with a stiff brush on a dry
surface. Pressure washing or wet scrubbing can put the efflorescence
in solution with water so it can be rinsed away. You must be careful to
rinse the entire surface with fresh water so that no residue is left to dry on
the concrete. Use an air jet or a wet vacuum to remove any standing
water. Any remaining water can cause new efflorescence to appear.
Cleaning on dry sunny days is best.
Hard Efflorescence (Milky Film)
Best results are obtained by using a proprietary masonry and concrete
cleaner with pressure washing equipment. The acid in proprietary
cleaning chemicals are buffered and blended with other chemicals to
provide effective cleaning without damage to the surface when used
properly. Always refer to themanufacturers recommendations for proper
dilution, application and protection of adjacent surfaces. Cleaners are
generally applied in sections beginning at the lowest point of the surface.
If the area is large, a sprayer is an efficient means to apply the cleaner.
The chemicals are scrubbed on the surface, then pressure washed away.
Results can be verified after letting the area dry for 24 hours. In most
instances one application is sufficient. However, in severe instances of
efflorescence, a second application may be necessary.
Note:
All acid based cleaners and acidic residues are dangerous to
cars, plants and people. Wear proper safety gear and take adequate
precautions. It is always recommended to do a small scale test section
to determine dilution ratios and effectiveness before a full scale cleaning
operation are performed.
Natural Process
If no attempt is made to remove efflorescence it can naturally breakdown
after a period of time. Soluble calcium hydrogen carbonate gradually
JAN 2010
CASTinTACT
®
| maintenance & protection guide