This is based on the fact that the asphalt cement, which is the material that binds the sand and small bits of stone together, remains malleable for a long length of time. This attribute makes the blacktop resistant to cracking if properly installed.
How Driveways Begin Developing Cracks
When asphalt is exposed to sunlight and air beyond a certain period of time, it starts losing its malleability and begins to oxidize. The sun's ultraviolet rays also cause the asphalt cement to breakdown. This is when problems start occurring.
Once the oxidizing begins, the material starts getting brittle. The binding effect that is present between the asphalt and the stone particles and sand, also known as aggregate, starts to come apart.
These sealers act as a protective shield on the paving, preventing sunlight and air from causing damage to the asphalt cement. They also protect the paving from the ultraviolet rays of the sun, and prevent ice and water from seeping into the driveway, which causes it to disintegrate.
Types Of Sealers
Traditional Sealers : These consist mainly of the same asphalt that is used in the paving itself. It is usually mixed with an emulsifier, which is a soapy compound, and water. The lifespan of this sealer is the shortest, and it hardly offers any protection against the sun's ultraviolet rays.
Coal Tar Sealers : This has refined coal tar. It is effective against oil and gasoline. Motor oil and gasoline can dissolve the asphalt cement in the paving. The sealer has an emulsifier and small clay particles which help to apply it easily. Some varieties are also modified with polymers, giving longer life, rich color, and extra protection against UV rays.
Acrylic Polymer Sealers : This is the most expensive and completely synthetic type. It is usually used on tennis courts. Manufacturers make it in black color for using on driveways. It provides the most effective overall protection and usually lasts twice as long as compared to other sealers.
It is usually mixed with sand. As far as sealing is concerned, sand is a very beneficial ingredient. It seals the pores on the paving, improves car and foot traction, and also increases the life of the sealant on your driveway.
Applying the Sealing
According to the manufacturers, once the new asphalt is laid, it should be allowed to cure for around a year, after which it should be given a protective coat of sealant.
Most homeowners use sealing on their driveway too frequently, as in every year. The disadvantage of this is that it can lead to a build up of the sealer, eventually resulting in peeling, and increasing the possibility of it getting tracked indoors. Vinyl flooring, for instance, can be stained permanently by a sealer even if it is cleaned promptly.
Manufacturers and contractors advise that sealing every three years is adequate for most driveways, except in regions where conditions are exceptionally harsh, like deserts. A rule of thumb is not to apply a new coat till the previous one has worn off which will happen at various rates according to the traffic, exposure to weather conditions and sunlight.
Another indication of it being time to apply a new coat of sealant is when the asphalt begins to gray, which is an indication of oxidization of the surface, resulting in loosening of the binder that binds the aggregate.