The change in color from rich black to grey is the warning sign.....the pavement surface is becoming worn, porous, and rough. As the asphalt binder weakens and loses flexibility, the aggregate stone in the pavement loosens. Over time, heat, cold, water and air attack the binder in asphalt pavement. They stress, oxidize and weaken it, destroying its flexibility. Spills of gas and oil soften the binder and hasten its destruction. Now water can penetrate deeper, further accelerating binder deterioration. Aggregate stone begins to loosen, and cracks and potholes soon form as vehicle traffic exploits pavement weaknesses. In short order, major repairs are required or an entirely new layer of asphalt is needed.