This year, and every year for the foreseeable future, your city, town, or county is likely to spend millions of dollars maintaining their pavement infrastructure. Large municipalities frequently spend upwards of 5 million dollars or more every year to maintain their roads. This is because the pavement network that you utilize every day is the single most valuable visible asset that a city owns and maintains.
Constant and ever-increasing traffic on these streets means that the pavement network is consistently deteriorating. The City must take an active, preventative maintenance approach if they want to prevent such a vital asset from deteriorating to the point where costly reconstruction is needed. In the pavement management industry this is called, “Pavement Rehabilitation”.
The type of rehabilitation method used will vary depending on the condition of the pavement and the amount of traffic it normally receives. In order to optimize their budgets, a City must be familiar with various pavement rehabilitation methods that are suitable for different types of pavement distresses.
Common Asphalt Distress Rehabilitations
Raveling is the presence of loose asphalt debris on the pavement surface. It increases the roughness of a street, while also reducing skid resistance. Light and moderate raveling is commonly a follow-on effect of another pavement distress, and can be found in areas around potholes, improperly sealed cracks and poorly maintained patches. In this case the loose material should be swept aside and the source distress should be properly patched or sealed.
If the raveling is severe and there are no other source distresses present, it is likely that the raveling is a result of inadequate compaction during the initial pavement process. In this situation a thin to moderate overlay will be needed.
Snowplows, studded tires, and tracked vehicles are also known to cause raveling. Road segments where vehicles of this type frequently drive should be monitored often and patched accordingly.
Bleeding is the presence of free asphalt binder on the surface of the roadway. This can be a symptom of poorly mixed aggregate materials in the initial surface paving of a street. Minor bleeding should not be alarming as it does not reflect poorly on the overall base construction of a street. Severe bleeding, however, may reduce skid resistance, especially when wet.
Though minor bleeding can be addressed through the light application of coarse sand (to absorb the excess asphalt binder) major bleeding should be shaved away using a motor grader or heater planer.
Maintenance on this type of distress is usually deferred until more critical rehabilitation methods are needed in the area.
Patching is an area of pavement that has been repaved in order to fix a localized distress, such as a pothole or severely cracked area. The presence of patching impacts the roughness score of a street. This impact can be minimized through properly smoothing and water sealing the patched areas. Patches that are not properly sealed will result in raveling which elevates the roughness even further, while reducing vehicle traction. Streets that have been patched frequently and also display cracking over previously patched areas should be considered as candidates for a new overlay.
Longitudinal and transverse cracks can often be fixed through a waterproof sealing process. In the case that the cracking is severe (>1/2inch width) removal and replacement with an overlay may be needed. Although this type of distress does not directly reflect poorly on the structural condition of a street’s base, if left unchecked they will compound into alligator cracking which can spread very rapidly and degrade the overall integrity of a street.
Alligator cracking: For this type of distress sealing is generally not going to be effective. If the cracking is small and localized it may be dug out and replaced with a patch. A large section of alligator cracking is a common early indication of pavement structural failure and must be fixed with a thick HMA Overlay. If this does not happen the cracks will fill with water and soon be replaced by potholes.
Edge cracking spreads very quickly so even light edge cracking should be waterproof sealed as early as possible. If the cracking becomes more severe, damaged areas of the road must be removed and replaced with an overlay. Make sure to reexamine the drainage system of a edge cracked segment before deferring maintenance. Pavement segments that display frequent edge cracks and also have poor drainage may be on the verge of severe base failure. This can result in very costly repairs 5-10 years later.
Rutting is dentations caused by vehicle traffic over certain areas of a pavement segment. Though slight rutting is often ignored until farther distresses are observed, heavy rutting (>1/3 inches deep) can be a concern and should be leveled and replaced by an overlay. Repeated vehicle traffic over severely rutted areas can not only cause further base distress on a street, but it can also result in vehicle damage.
Potholes can get substantially worse over time and present a major danger to motorists. They must be replaced with patches and fillings as early as possible. Areas with frequent potholes may require a complete reconstruction, especially if there is poor or no drainage present in the area. Potholes often form when alligator cracked areas fill up with water, so to prevent this from occurring make sure alligator cracks are patched as soon as possible and proper drainage is in place to prevent sitting water on the pavement.
To learn more about spotting asphalt failures, check out "How to Spot a Failing Street" - An IMS Whitepaper.