Did you realize that in attempting to maintain your asphalt pavements by placing
water-based “sealcoats” on them, you could be losing one-third to
one-half of the pavement’s useful service life? An asphalt pavement placed
today should typically yield 15 to 20 years of practical service life if
nothing is done in terms of maintaining it.
To keep the rich black appearance of the new asphalt surface and extend the life
of this investment, many associations adopt a maintenance program centered
around “sealcoating”. If you decide to implement such a program, you can
expect the following course of events.
Two years after the pavement is laid, a coal-tar emulsion of water-based
sealcoat is put in place on the pavement. Soon after the coating goes down, it
appears to wear off in driving lanes. As the selacoated pavement ages, small
hairline cracks begin to appear on the surface, causing concern. Your budget,
however, calls for sealcoating every three years, so when the pavement
is five years old, you place a second sealcoat on it. With time, this coating
also wears and what were hairline cracks become larger, as do your concerns.
In keeping with your budget, the next sealcoat is applied when the pavement is
eight years old. As you wait and watch, the same degeneration of the sealcoat
takes place.
When putting together your maintenance budgets, you examine your asphalt
pavement areas. That pavement, which is now ten years old, has been maintained
with three sealcoats, applied three years apart. So now, at year ten of the
pavement’s life, the surface is so badly cracked in the areas where the coating
has not worn off that you feel your only solution to the unsightly, cracked
appearance is to overlay the pavement with a new layer of asphalt.
Look what you have done. You have spent good money over a 10-year period to
maintain your investment, only to have your maintenance practice force you to
overlay your pavement five to 10 years earlier than you would have to if you
done nothing at all.
With this scenario in mind, consider this question: Are sealcoats all they’re
“cracked” up to be?
I am not recommending that you forego maintenance; that would be impractical.
What I do recommend is to incorporate into your pavement maintenance program a
treatment that has been proven to extend the life of your asphalt pavements.
This will allow you to postpone the need for costly overlays or reconstruction.
The Florida Department of Transportation has developed a specification that
outlines the application of a material that is comprised of coal-tar oils and
coal-tar distillates, combined with a maltenous-type rejuvenator. This material
is named Pavement Dressing Conditioner (PDC) rejuvenator/sealer. When
applied to an asphalt pavement, PDC will seal and protect the pavement from the
deterioration that results from fuel spills and water damage and oxidation, as
well as restore flexibility and durability while revitalizing the asphalt’s
oils. The process is called rejuvenation, and its been proven
to work. Application of PDC rejuvenator/sealer every three to five years will
suspend the aging process of asphalt. When applied to older pavement, this
treatment will actually reverse aging.
The reason water-based or emulsion sealcoats fail has to do with their
composition. Because they are formulated with varying water content and
coal-tar solids, they form a rigid “laminate” or veneer on the pavement
surface. These coatings cannot expand and contract through daily thermal
cycling at the same rate as the coated pavement. The rigid coating is unable to
cycle with the pavement as the pavement heats up and expands during the day,
and cools down and shrinks at night. For this reason, hairline cracks form in
the seal.
Reapplying sealcoats to eliminate cracking is futile. The cracks will only
reappear and typically get larger. Subsequent re-cracking will actually migrate
into and damage the pavement itself.
PDC contains no water, thereby allowing the rejuvenator/sealer to penetrate into
and become an integral part of the pavement. By being in the pavement and not
just on it, the treatment expands and contracts with the pavement through
thermal cycles. The result: no unsightly coating cracks.
PDC gives true meaning to the word “maintenance”. The PDC treatment protects the
pavement with tough fuel and water-resistant coal tars. And the rejuvenator
portion soaks into the aging pavement to restore suppleness and extend pavement
life.
Pavement Dressing Conditioner (PDC) rejuvenator/sealer has been applied
throughout the state of Florida to pavements as varied as airport runways,
commercial shopping centers, apartments and numerous community association
roads and parking areas.
Article written by Bob Hegerman who was President of Asphalt Restoration
Technology of Florida from 1993 to 1999.