Causes of asphalt deterioration:
The most common cause is the accumulation of water in low areas. Over time, water accumulation can cause asphalt to crack and separate or alligator as it commonly referred to in the paving industry.

Another cause is excessive weight where the asphalt was not constructed to carry. The constant bearing weight of garbage or delivery trucks go over the exact same place day after day.

Asphalt patching methods:

• Surface patch
• Mill patch
• Remove and Replace

Surface patching is recommended when the underlying base is structurally sound and is typically used on depressed surfaces. This process is done by cleaning the area to be repaired and applying a liquid tack coat ( asphalt glue ). Then new hot mixed asphalt is placed on the patch area and machine rolled for a smooth and compacted surface. Because the surface patches are placed on top of existing pavement, the finished surface may be slightly higher with the edges blended in.

Mill patching is like the surface patch except the patch areas are milled down to ensure a flush tie into the existing asphalt (mostly used in tight drainage areas or trip points).

Remove and replace are used for more severe deteriorated areas, especially when the underlying base material has been affected. The patch areas are saw cut square. At this point excavation of the area is made (to a predetermined depth based on the subsoils) and new aggregate base is installed. Finally new asphalt is placed (at a predetermined depth) and compacted.

Benefits of asphalt patching:
All three applications are economical components of an overall pavement maintenance program. Timely asphalt patching is the prevention to more extensive and costly repairs while creating a safer environment reducing owner liability.