BENEFITS OF PATCHING

Stops Further Deterioration - A deteriorated area will continue to grow until treated. The deteriorated sub-base will contaminate the surrounding sub-base. This process will repeat until the problem is fixed. As it continues to grow, it will encompass a larger volume and subsequently cost more to repair. The sooner an area is treated, the less it costs to repair.

Limits Liability - In many cases the deteriorated asphalt contains loose gravel and stones or has created a hole. This could cause slip and fall issues or damage to passing vehicular traffic. The prompt repair of these problems immediately eliminates any liability risk or issues.

Restores Integrity and Value to Asphalt - In many cases, an asphalt parking lot represents the single biggest investment in site development. If deteriorated sections of the pavement are repaired as needed, the investment continues to hold it value. In contrast, a parking lot that has been poorly maintained can reduce the overall value of the property.

TYPES OF AREAS TO BE PATCHED

Fatigue Cracks

Description - Fatigue cracks are commonly called "alligator" cracks because they resemble the lines on alligator skin. They are almost always a maximum of 8 inches apart but can be as small as 1 inch apart. They are almost always present in an interconnected group. You will seldom see fatigue cracking in parking stalls.

Causes - Fatigue cracking is a direct result of excessive bending of the pavement surface under load. An asphalt surface, like most other engineering materials, will fail if subjected to repetitive and/or excessive bending stresses. In pavements, we call these deflections: the sub-base is damaged or eroded and can no longer support the surface asphalt and the surface asphalt begins to crack. Water intrusion into the sub-base can excel the sub-base erosion and cause deflection to start sooner.

Significance - Fatigue cracking can be an indicator of major problems, depending on the severity, extent and age of the pavement.

On fairly new pavements, less than 8 years old, isolated fatigue cracking (less than 8% of the pavement is involved) is often an indicator of slightly inadequate pavement layers or isolated low compaction. On that same pavement, an extent of 15 to 20% indicates more severe problems. Major rehabilitation methods will probably be needed.

Older pavements with fairly extensive (15% plus) alligator fatigue cracking are indicating that they have served their design life and need "renewal".

Solutions - If a pavement is over 6 years old, and has only isolated fatigue cracked areas, then digout and replacement is economical. The perimeter of the digout must be saw-cut, all existing materials removed to a depth of 5 inches for vehicle traffic and 8 inches for truck traffic areas, the existing layer recompacted and then the digout plugged with asphaltic concrete. These thickness' may seem excessive but remember, you are trying to patch a problem area that has failed for undetermined causes.

If the pavement is over 10 years old and has followed the general mode of failure and now has fairly widespread fatigue cracking (15% plus) of the area, digout repairs alone are seldom cost effective. The pavement has probably neared its life expectancy, and more major treatment is needed.

Potholes

Description - Potholes are severe manifestations of pavement fatigue cracking resulting in a total loss of asphalt surfacing in a localized area. This creates a hole in the road. It is not uncommon to have a pothole extend through or into the aggregate base.

Causes - Most pavements susceptible to potholing have a fairly thin asphalt concrete surface (2 1/2 inches or less) on an untreated aggregate base. Pavements that have severe alligator fatigue cracks begin to "pop" pieces out of the cracked areas, creating a hole.

Significance - Extensive potholing is an indication of severe structural problems. If allowed to remain unrepaired, they present a safety hazard to the user public.

Although rare, potholing on new pavement occurs when it is substantially structurally inadequate. Usually, potholes only occur as a result of other pavement defects.

Solutions - In the winter, potholes should be temporarily filled with patch mix to protect against vehicle damage or lawsuits.

In the spring and summer months, potholes should be permanently patched. The outside perimeter of the pothole should be saw-cut and the damaged materials and any temporary patching material removed to a depth of 6 inches. The edges of the saw-cut pavement should receive an application of tack coat, and the hole should be filled with compacted hot asphalt.