Asphalt Seal Coatings
Now some people will tell you that rejuvenation is snake oil and is a waste of money and that a good seal coating is the way to go. Now let’s take a serious look at some of the seal coating systems available for pavement maintenance. Seal coating systems are designed to seal off the surface of the asphalt mat filling in the voids of the pavement so as to provide a tough wearing surface that will prevent any water from penetrating the mat. By keeping the surface sealed, a seal coating is keeping the damaging ultra violet of the sun and the elements of the weather off the pavement, while also keeping sealed into the asphalt mat the necessary oils that are required to keep the asphalt mat flexible and healthy. The drawback to a seal coating system is that once it begins to wear off the surface it no longer provides any protection from the elements in the areas where it has worn off the surface of the asphalt pavement.
Most seal coating systems are mineral filled and rarely have more than 20% bitumen content which is normally only enough bitumen to bind the mineral to the pavement and cover the pavement surface. This low bitumen content in conjunction with the absence of any light oils or maltines prevents a seal coating from providing any rejuvenation to the asphalt pavement.
One of the most popular seal coating systems across the country is Coal Tar Pitch Emulsified Seal Coating. Coal Tar Pitch is generally emulsified with water and mixed with a mineral aggregate and/or sand to give the product body and wear-ability. The major benefits of coal tar is that the product is fuel resistant and generally will provide superior abrasion resistance therefore it will wear and look cosmetically appealing for a longer period of time. How ever, Coal Tar Seal Coating does normally begin to wear within a year of application and once it begins to wear off the surface it provides no protection to the asphalt mat in the areas where it has worn off.
Coal tar pitch is a by-product of the coking process of coal used in steel mills. Like petroleum crude it is refined through a distillation process to produce products like xylene, benzene, creosote, and several other types of products, but like asphalt it is the black sheep of the coal tar pitch industry. Unlike asphalt, coal tar pitch is in no way chemically or otherwise compatible with any type of petroleum product including asphalt. Due to this reason coal tar pitch cannot provide any rejuvenation at all to an asphalt pavement. In order to get coal tar to properly adherer to asphalt pavement generally a polymer additive needs to be added by the applicator prior to application to prevent the sealer from delaminating from the pavement surface. So, the question is why put a product that is not compatible with a petroleum product on a petroleum product such as an asphalt mat. The answer is a coal tar is generally more cost effective.
Coal tar also has other drawbacks. Coal tar contains benzene along with several other listed cancer causing compounds. In addition, the main issue with coal tar is the fact that the vapor of the product is carcinogenic and can cause serious health problems with continues use. Some of the early signs are burning of the skin similar to what happens when one lets gasoline dry on the skin. It has been documented by the National Institute For Occupational Safety and Health (NIOSH) in report No. NIOSH-78-107 that states: “Vapors can cause serious lung problems resulting in cancer.” This hazard will remain present as long as the product gives off a vapor that one can smell.
Due to obvious health and environmental concerns the use of coal tar pitch has been restricted is some states such as the state of New Jersey and the state of New York. It has been banned in the state of California and the city of Austin, Texas just to name a few.
An alternative to coal tar pitch is asphalt based emulsified seal coat. Asphalt based emulsified seal coatings are similar to coal tar in the fact that most are mineral filled and are applied and perform in the same fashion; however, asphalt is used as the binder. Asphalt based emulsified seal coatings do not have the health hazards associated with coal tar. However, asphalt based seal coatings tend not to wear quite as well as coal tar and if fuel resistance is desired a vinyl latex must be added to the product which results in increased cost per gallon.
-Todd M.
Call Love’s Enterprises LLC today for Denver asphalt maintenance services – 303-816-9090