Asphalt should be sealed when either the original black asphalt cement has worn off the stones or the subsequent coat of sealer has worn off revealing the actual pieces of stone aggregate. Sealant should typically be applied every three to five years. A new seal coat will make your old asphalt look new again and help extend its usable life. Before seal coating asphalt, we recommend a crack filling procedure as well.
 
If you are considering having your asphalt sealed, make sure you know what type of product will be used. Some companies use a coal tar-based product that may contain cancer-causing chemicals and is known to contaminate waterways. Elam uses RS-90 instead, which is a Gilsonite-based product that actually penetrates and rejuvenates the surface of the asphalt rather than simply coating it.
 
For more information about harmful coal tar-based sealants, click here