Asphalt Driveway Sealers
DEAR TIM: I was reviewing a quote I received to have my asphalt drive sealed. But it dawned on me that the streets in my community never get sealed. Is sealing an asphalt driveway really necessary? If so, when should they be sealed? Ron P. Westchester, OH
DEAR RON: Touche! I'll bet you were the captain of your high school debate team. With a point such as that, you can definitely win an argument or two. But in this case, I happen to have a stronger rebuttal point!
There are several reasons why you don't see highway maintenance departments using traditional sealers on roadways. The heavy volume of traffic on the average road would rapidly wear away a surface coating of asphalt sealer. Roadways are also built differently than the average residential driveway. The engineers and government officials responsible for the design and maintenance of public roads plan for re-paving. In other words, since they know they can't seal, they plan ahead knowing the road must be re-paved every so many years.
The asphalt cement is a component of your driveway and public roadways. It is the glue that holds together the gravel and sand particles that actually make the superb driving surface. But the asphalt is damaged by the sun's ultraviolet (UV) rays and oxygen in the air. The UV rays and the oxidation cause the asphalt to become brittle. Brittle asphalt can crack. Cracks allow water to enter the paved surface. This water can freeze in colder climates causing further damage.
The traffic on roadways actually wears away the brittle asphalt and exposes fresh asphalt. Furthermore, oil drippings from cars and trucks that get spread over the road surface actually acts as a low-grade sealer. But typical residential driveways don't get the traffic that roadways receive. Furthermore, oil spots on driveways are taboo.
The bigger issue for residential asphalt driveways is cracks. Cracks that allow water to penetrate into the gravel base are a far greater threat to the long-term health care of your driveway. Water that enters the gravel base can then soften the soil under an asphalt drive. If this happens, the weight of the cars going over this soft area can cause the paved surface to crack in even more places. Remember, asphalt paving is actually a flexible pavement. The strength of asphalt surfaces comes from strong soils and a strong base material under the finished surface.
Keep in mind that asphalt sealers are simply coatings that penetrate slightly into the asphalt surface. For the most part, they lay on top of the pavement. If you seal too often, you simply are adding layers of asphalt that can peel off. Asphalt drives should be sealed when you can clearly see the color of the stones that are used to make the asphalt paving.
Where I live we use limestone stones to make asphalt paving. Left alone to weather, an asphalt driveway obtains a uniform color of gray. There are asphalt drives in my neighborhood that have not been sealed in 15 years. Had they been sealed three times in that time period I can't say that the driveway would be in any better condition.
Absolutely do not seal a brand-new driveway. Fresh asphalt contains light-weight oils that eventually evaporate into the atmosphere. These oils are responsible for the tender nature of fresh asphalt. As these oils evaporate, the asphalt gets harder and harder. Sealers prevent this evaporation. Seal a new asphalt driveway and it may permanently stay soft.
When you purchase asphalt crack and driveway sealers, use pricing as a barometer. Usually higher priced products contain higher quality materials. Pay attention to any temperature limitations on the product labels. Be sure the products can cure properly.