- 1. Why are two thin
coats better than one thick coat? Sealer applied in two coats
dries and cures much better than one thick coat
application. Remember sealers are water-based coatings, which cure
through the process of water release (evaporation). A thin coat will
release water much faster than a thick coat. If applied in one thick
coat, sealer will have a tendency to hold water and stay soft for a
longer period of time, possibly causing tracking.
- 2. Why did the
sealer fail or peel? Peeling problem is caused by sealer not bonding to
oil spots or any other surface contaminants like dirt, grease, etc. or
oxidized pavements. All the areas shall be thoroughly cleaned, oil
spots shall be primed with specialty primers. Oxidized pavements shall
be treated with a diluted coat of sealer or asphalt emulsion.
- 3. What causes white
streaks in the sealer? Possibly due to incomplete mixing of clays and
fillers in the manufacturing process of the sealer. Your sealcoating
manufacturer should be contacted to rectify this problem
- 4. Why
does the sealer dry gray? If the problem persists and the sealer does
not cure to its normal charcoal black dried color, the manufacturer
should be consulted. It is possibly due to higher clay and filler
content in the sealer itself. If the problem is temporary i.e.
after a few days in full sun it will cure to its normal color, the
initial graying is due to either sealer curing under shaded areas or
the surface containing too much moisture. Temporary graying can also
be eliminated through the use of specialty additive that helps sealer
dry faster and at a uniform rate
- 5. Why does brand
"X" burn more than brand "Y"? What conditions
aggravate burning? What precautions shall be taken to avoid burning?
What is the industry doing about it?
Sealcoatings based on coal tar are manufactured
using refined coal tar within a very narrow range of properties. Coal tar
suppliers remove most of the lighter components (potential irritants),
quite effectively.
In
our opinion the ambient conditions or improper skin protection causes the
skin irritation and burning sensation. On hot humid days the vapors coming
out of the sealer do not dissipate fast enough and have a tendency to
deposit on the skin, causing the irritation. People with lighter skin are,
therefore, affected more than people with darker pigmentation. Protective
clothing and equipment are a must for safe handling of sealcoatings. Wear
long sleeved shirts, pants, impervious boots and gloves and use safety
goggles. Use a skin cream with a high sun screen factor on face and other
exposed body parts. Read the Material Safety Data Sheet (M.S.D.S.) supplied
by the manufacturer.
The
industry professionals association, Pavement Coatings Technology Center
(PCTC)
at University of Nevada at Reno is currently researching into the
components in the refined coal tar that cause skin irritation and possibly
reducing those components, without jeopardizing the sealcoating properties.
- 6. Why does the
sealer wear out faster in traffic lanes, entrances and exits? It is an adhesion problem. The surface aggregates in these
areas become smooth (polished) over the years of usage. For any
coating, including sealcoatings, to bond properly, it is imperative
that surface should by sufficiently rough. Our recommendation is to
use a specialty primer to prime faster traffic lanes, exits and
entrances. These primers penetrate the smooth polished aggregates and
allow the sealcoating to bond effectively.
- 7. How soon I can
sealcoat a freshly laid asphalt? As soon as
the surface rids of light oils, through oxidation. To ensure spread
some water on the surface. It the water spread evenly without beading,
you are ready. It is also called "water break test". It
usually takes about 4-6 weeks, depending on geographical locations.
- 8. While spraying
how do I know if I am applying at the recommended coverage rate e.g.
0.12 gallon/sq. yard? The coverage rate dictates
the film thickness which can be measured by a simple film thickness
gauge, available at most paint stores. Select a 10’ x 10’ area of the
pavement and place a 3"x 6" metal plate in the center. Spray
sealcoating in this area and lift the metal plate before the
sealcoating dries. Use the film thickness gauge to determine the wet
film thickness. The reading will be in mils (1/1000 of an inch).
Compare this reading with the desired film thickness for 0.12 gallon/
sq. yard coverage which is 21 mils.
- 9. What type of
striping paints to use and how soon can the lot be striped? Water based traffic paints are preferred . Allow at
least 24 hr. after the application of the final coat of
sealcoating.
- 10. Can you explain
sieve size, % retained, % passing, etc.? Sand or the other aggregates added to sealer must
fall within a set of particle sizes, neither too coarse nor too fine.
This is ascertained by the sieve analysis which means that sand has
been sifted through a set of screens with varying mesh sizes meaning
the openings in the screen. Percent retained means how much of 100
grams of sand was retained on the screen and % passing is how much
passed through the screen. Use your manufacturers recommended
grades.
- 11. Why should we use
sand? Sand is used for traction,
skid resistance and also to provide a uniform texture to the
surface.
- 12. Why use latex? The use of latex additives is very common. There
are many latex additives to impart all types of performance
advantages. For example;
- Rubberizing additives
improve flexibility, durability, toughness, etc.
- Faster drying additives
help sealers dry fast.
- Thickening additives
build the viscosity of sealcoating diluted with large amounts of
water.
- 13. Why apply two
coats, when one coat looks good enough? Appearance is only part of the benefits.
The sole purpose of sealcoating is to protect and preserve the
asphalt. One coat will possibly provide only half of the protection
and wear out in less than half the time. You will have to sealcoat
more frequently if you used only one coat.
- 14. How much water
can I use? Follow the manufacturers’ recommendations. Normally
25-30 gallons per 100 gallons of concentrated sealer are recommended.
Higher percentages are recommend for mix designs that use additive and
extra amounts of sand.
- 15. What happens when
you use different additives (different suppliers) in the same tank.
The viscosity went haywire? The
viscosity went haywire because the additives were not compatible with
each other. Do not mix different additives and stick to manufacturer
recommendations. Also the manufacturers’ warranty may be void if you
use other additives.
- 16. What is the deal
with specifications using excessive amounts of sand, e.g. 18 lb. of
sand in one of the FAA Specifications? Those are special sand
slurry specifications and not used commonly for sealcoating
specifications. The industry recommends a maximum of 8 lb. of sand per
gallon. Very high sand loading (18 lb. for example) will result in a coating
that will be poor in flexibility, adhesion and chemical
resistance.
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