Asphalt pavement is made from 95% stone and 5% liquid asphalt (the glue). As pavement ages it weathers, turns gray, dries out and becomes brittle. Sealcoating protects the pavement from the elements by acting as a barrier against the ice, water and sun damage. This slows the deterioration and prolongs the service life of the pavement.
A parking lot should be sealcoated 12-18 months after installation and then sealed every 3 years after that.