While the Plantmix Asphalt Industry of Kentucky (PAIKY) remains focused on our mission to promote, design, produce, and construct hot mix asphalt pavements – we frequently receive calls and field questions regarding sealing products and maintenance techniques. The information below is intended to provide some very basic information about sealing asphalt pavements. A properly applied sealcoat is designed to protect the surface, fill the small surface voids, and extend the life of the pavement.
Pavement Cracks
All pavements will experience a slow rate of deterioration due to weather conditions – regardless of traffic loads. Over time, an asphalt pavement will turn from dark black to light gray through a process called “oxidation”. Oxidation causes the pavement to become more brittle and small cracks will eventually develop in the surface. These cracks in a pavement will allow moisture to seep in below the surface, saturate the soils below, and accelerate the pavement distress. If not maintained, small cracks will lead to larger cracks and additional deterioration. A sealcoat should be applied while the cracks are still small (1/8 inch wide) and is intended to fill those cracks and prevent them from becoming wider. Larger cracks (exceeding ¼ inch wide) should be cleaned and filled (a process called “crack sealing” or “crack filling”) by a professional contractor. Cracks should be cleaned of all debris using mechanical tools and by blowing hot compressed air into the crack to remove any moisture prior to sealing.
Sealcoating Driveways or Parking Lots
Sealcoating is a method of protecting your asphalt pavement by applying a coating to the pavement surface. The American Public Works Association (APWA) brochure entitled “Caring for your new Asphalt Pavement” suggests that Sealcoating should not be applied immediately after a driveway or parking has been paved. The APWA recommends waiting at least 90 days but suggests that a driveway be sealed within the first year and every 2 or 3 years after that.
Selecting your Sealer
Many homeowners try to do sealing themselves but hiring a maintenance professional will give you better results. Products found in home improvement stores do not have aggregates and may lack the quality to withstand the weather and traffic when applied to the pavement. Professional contractors are able to heat the materials and have better equipment for applying them uniformly to the pavement surface. Sealers used by professional contractors are typically thicker, have a higher percentage of solids for filling cracks, contain additives to accelerate drying and reduce cracking, and have the proper aggregate content to provide an abrasive surface.
The sealing products themselves are usually classified as either an “asphalt emulsion” or a “coal tar” sealer. Both products are widely used and effective. Generally speaking, coal tar sealers will provide a longer life, are more abrasive, resist fuel spills, resists ultraviolet rays from the sun, but they are typically more expensive than asphalt emulsions. Asphalt emulsions are generally not very resistant to fuel spills but some sealing products will modify the blend with special additives to make it more resistant to gasoline and oil spills.
Weather Limitations
In Kentucky – the general rule of thumb is that sealcoating is performed between May 1st and October 31st - “Derby Day to Halloween”. Due to temperature and moisture limitations – sealcoating is not recommended in the Winter and early Spring months. The pavement must be dry prior to a sealcoat application – preferably following several days of warm temperatures without rain.
How Many Coats and Drying Time
Similar to painting a room in your house – one coat is usually not sufficient. Additional, one thick coat is more likely to crack and not as effective as two thin coats. Typically, these products should be applied at a rate of about 0.2 gallons per square yard. Most sealers are applied in two coats and it is essential that the first coat dry before the second coat is placed. Two coats won’t cost much more than a single coat and should last longer and provide a better appearance. Water must evaporate from the material and, if placed too soon, the water from the first coat is trapped and tends to cause the second coating to stay soft – especially during hot, humid days. If the sealcoat is not allowed to dry completely, vehicle traffic will cause tire marking, tracking, premature failure, and may also stick to your shoes. At a minimum, allow the sealcoat to dry overnight (without traffic). Ideally, allow 24 hours of drying time.
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