Periodically sealcoating your asphalt driveway helps to protect it from breaking down by adding a protective layer. When asphalt is exposed to oxygen in the air and ultraviolet light from the sun, it will start to oxidize. Oxidized asphalt is very brittle and has an unattractive gray color, so protecting your driveway from oxidation both preserves its appearance and its durability. When sealcoating your driveway, you'll be able to choose between a coal tar sealer and an asphalt emulsion sealer. To learn the difference between the two and to find out which one protects your driveway the best, read on.
Coal tar is the substance that's leftover after coal is burned to create energy. It's applied to asphalt driveways in order to protect the asphalt underneath from motor oil and ultraviolet light. In order to apply it, a sealcoating service heats it up in a cauldron in order to liquefy it, then sprays it onto your driveway in order to create a thick layer of coal tar on top of the asphalt.
The main advantage of coal tar is that it prevents motor oil from damaging your asphalt driveway. Oil leaking from your car will bind to the asphalt and weaken it, which will eventually result in a pitted area in your driveway when the weakened section breaks apart. In addition to protecting your driveway from oil, coal tar also shields the asphalt from ultraviolet light and open-air, preventing it from oxidizing and weakening.
Unfortunately, coal tar contains a significant amount of polycyclic aromatic hydrocarbons, which can potentially be hazardous to the environment. The coal tar can chip off when you drive over it, allowing the coal tar dust to make its way into nearby lakes and streams when it's carried away by rainwater.
Some cities have banned the use of coal tar for sealing driveways due to the hazards that polycyclic aromatic hydrocarbons can pose to aquatic wildlife in the local waterways. Thankfully, this isn't as much of a concern when using coal tar on residential driveways, since residential driveways see less vehicle traffic compared to roads or parking lots — less traffic means that less coal tar dust will be generated.
Asphalt emulsion sealers simply consist of asphalt, water, and a solvent that allows the asphalt and water to mix. They're applied to a driveway by rolling them on in a thick coat. Once the water and the solvent have evaporated, the asphalt will harden and bind to the existing asphalt surface on your driveway, protecting the layer underneath.
As noted above, asphalt emulsion sealers don't protect your driveway against motor oil. It's the same substance as the original asphalt, so it breaks down the same when exposed to oil. However, it does serve as a sacrificial layer against any oil stains — the asphalt emulsion layer will be damaged instead of the asphalt in your driveway. Like coal tar, an asphalt emulsion sealer will protect your driveway against air and ultraviolet light, which helps stop your asphalt driveway from oxidizing.
Which Sealer Protects Your Driveway Better?
Ultimately, coal tar is the most durable choice for sealcoating your asphalt driveway. If it's not banned in your area due to environmental concerns, its ability to withstand oil spills makes it the superior option for keeping your asphalt driveway protected. Asphalt emulsion sealer can still protect your driveway from damage caused by air and ultraviolet light, but its vulnerability to oil means that it isn't the best protective option. However, using asphalt emulsion does eliminate the environmental concerns posed by coal tar.
If you want to restore the appearance of your driveway and protect it from the elements, call a sealcoating service in your area and have them apply a sealer to your driveway. Coal tar needs to be applied by professionals due to the fact that you need to heat it up in order to apply it, and professionals have access to higher-quality asphalt emulsion sealers with a lower water content that does a better job of protecting your driveway compared to what you can purchase at a home improvement store. Hiring a pro to sealcoat your driveway ensures that it'll look great and receive maximum protection.