I have had the opportunity to respond to many questions pertaining to sealcoatings, based both on refined tar and asphalt, during my many years of lecturing and day to day service to our customers. The following is a condensed list of questions and my answers which are frequently asked.
Q.1. Why are two thin coats of a sealcoating is better than one thick coat?
A.1. Sealcoatings applied in two coats dries and cures much better than one thick coat application. Sealcoatings are commonly water-based coatings, which cure through the process of water release (evaporation). Also, sealcoating film dries from top to bottom, meaning top layers dry faster then from the bottom layers. A thin coat will release water much faster than a thick coat. If the sealcoating is applied in one thick coat instead of the recommended two coats, it will have a tendency to hold water and stay soft for a longer period of time, possibly causing tracking.
Q.2. Why apply two coats, when one coat looks good enough?
A.2. 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 will wear out in less than half the time. You will have to sealcoat more frequently if you used only one coat.
Q.3. Why did the sealcoating fail or peel?
A.3. Peeling is caused by sealcoating not bonding to oil spots or any other surface contaminants like dirt, grease, etc. or oxidized pavements. Prior to sealcoating application, the pavement surface shall be thoroughly cleaned, oil spots be treated with an oil spot primer. And oxidized surface be primed either with a specialty primer or a thin coat of the sealer or a tack coat.
Peeing and dis-bonding, may also be caused by freezing temperatures during the final cure process, before the film was fully cured. Freezing temperatures will shatter the sealcoating bonds from the bottom layers of the sealer film.
Deposit of tree sap in the pavement profile. The failure is seen as the flaking of the sealer.
Sealcoating over a very hard coating, e.g. Gilsonite-based. The failure appears as chipping because the top coat does not bond and flex with the bottom coat.
Q.4. What causes white streaks in the sealcoating?
A.4. It may be an indication of a problem with the base itself. The limestone from the base may be coming up with water though pre-existing cracks in the pavement. (details in a previous article published here).
If not, then contact your sealer manufacturer to be assured that that the material in question was processed adequately to mix the clay and fillers during the processing.
Q.5. Why does the sealcoating dry gray?
A.5. The graying is caused by sealcoating drying under less than ideal conditions, e.g. shaded areas, cooler temperatures, high humidity, etc. The problem is mostly temporary i.e. after a few days in full sun it will cure to its normal color. Temporary graying can also be eliminated through the use of specialty additive that helps sealcoating dry faster and at a uniform rate. If the problem persists and the sealcoating does dry to its characteristic charcoal black color, the manufacturer should be consulted.
Q.6. Why does the sealcoating wear out faster in traffic lanes, entrances and exits?
A.7. Aside from the obvious reason of more traffic in those areas, it could be an adhesion problem, If the wear is excessive. 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 the surface be 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.
If you have any further questions about Pavement Deterioration or Sealcoating or have a project that you need completed, then contact PTG Enterprises aka My Pavement Guy today by calling 410-636-8777 or click here today! The asphalt experts here have managed hundreds of pavement projects and have the experience you need.
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