Although it would be impossible to address every type of asphalt pavement, especially as cost, climate, and traffic vary so widely, in most cases the math works out roughly the same: for less than the cost of repaving in 10 years, you can sealcoat a pavement three times, increasing the pavement's life to 15 or more years.
More than skin deep
A well-maintained facility bespeaks of success and instills a sense of security. Your pavement is your welcome mat. If it is in poor condition, it will reflect on you. That does not mean, however, that you want to sacrifice quality for looks.
In the sealcoating industry we use the term "cosmetic job." The term is used to refer to any seal-coating application whose purpose is other than maintenance. An example of a cosmetic job is a very low cost application used to blacken a pavement solely for the purpose of selling the facility.
When you buy a $15,000 car you know that a $45,000 car will look, feel, and sound better, but you probably also realize that both will get you to the same place with virtually the same amount of reliability. The same cannot be said for the sealcoating industry. There is no such thing as a low-cost, cost-effective, maintenance sealcoating application. A cosmetic job may cost one-third of a maintenance application, but you will be lucky if it lasts one-sixth as long. And, except for longevity, there are very few people who can tell the difference between a cosmetic job and a maintenance application.
There are two basic maintenance seal-coating materials: coal tar pitch emulsion and asphalt emulsion.
Coal tar pitch emulsions and asphalt emulsions are both waterborne products. In general, coal tar pitch emulsions are considered more resistant to weathering, gasoline, and other automotive fluids. These emulsions have been successful in the eastern half of the country. On the West Coast, asphalt emulsions are used more widely than coal tar. While the following will deal primarily with coal tar emulsions, the concepts apply to both products.
You should start maintaining an asphalt pavement as soon as the asphalt is cured. ASTM D 3423 Standard Practice for Application of Emulsified Coal-Tar Pitch (Mineral Colloid Type) says to allow conventional hot-mix asphalt surfaces to age a minimum of 30 days prior to the application of the sealer. It also warns that you should extend the curing period during cool or cold weather.
When new pavement is properly sealed, both sealcoating life and pavement life are dramatically improved. Generally the sealcoating on a new pavement will last five years, where it will last only three years when applied to a three-year-old pavement. Although some may argue the numbers, most will not argue the benefit of budgeting sealcoating as part of the cost of a new pavement.
As asphalt ages, the asphalt binder erodes or deteriorates leaving exposed aggregate. The asphalt color changes from black to a light brown or gray as it ages. It is typically described as being oxidized.
The description of the application should include the sealer by name, the number of coats, the formula (or mix), the coverage rate, and the method of application. Most of this information can be abbreviated by referring to an attached manufacturer's application specifications.