Proper preventative maintenance, like seal coating, can help ensure that the existing pavement structure will last for many decades. Asphalt streets consist of a 1 1/2 to 2 inch layer of asphaltic concrete most people just call asphalt or pavement. Over time, the asphalt ages, weathers, and oxidizes. It becomes brittle and cracks. While the old surface appears smooth, it contains hairline cracks that, if not treated, would continue to widen, deepen and eventually form potholes.