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3 Common Types of Asphalt Distortion

A road made of asphalt
Both residential and commercial property owners prize asphalt for its unique combination of durability and good looks. When correctly installed, an asphalt driveway or parking lot can provide years of worry-free use. Yet even the best asphalt surfaces may fall prey to certain forms of damage as the years go by.

One category of asphalt damage goes by the name of distortion. Distortion affects the shape and behavior of the asphalt's surface, leading to a bumpier roadway. Furthermore, distortion may lead to other forms of damage by allowing water to more easily pool up. This article takes a closer look at three common types of asphalt distortion.

1. Rutting

Rutting involves the formation of noticeable depressions along wheel paths. The weight of passing vehicles forces the asphalt into a more compressed state. The downward forces acting on the areas of rutting may also lead to what paving contractors refer to as shearing, which involves the formation of raised ridges along the edges of the ruts.

Rutting breaks down into two sub-categories: mix rutting and subgrade rutting. Mix rutting happens when just the asphalt becomes distorted; the underlying gravel subgrade, by contrast, remains unaffected. Subgrade rutting involves depressions forming in both the asphalt and the underlying subgrade.

Subgrade rutting usually occurs as the result of insufficient pavement preparation. The subgrade may not be thick enough; likewise, the soil beneath the subgrade may not have been compacted adequately. Mix rutting often occurs when the asphalt itself did not receive adequate compaction.

Ruts allow water to pool up on the asphalt, hastening the rate of raveling and other types of damage. That water also increases the risk of vehicles hydroplaning and losing control. Contractors repair rutting by leveling the pavement and overlaying it with a fresh layer of asphalt. Ruts with a depth less than 1/3" may not require treatment.

2. Depressions

Beginners often confuse rutting and depressions. While rutting does involve the literal formation of depressed areas, those areas always correlate to the wheel paths of vehicles. Depressions, by contrast, affect larger portions of the pavement, and seldom exhibit a direct relationship to vehicular weight.

Pavers define depressions as areas whose elevation differs slightly from that of the surrounding asphalt. You may not see depressions when the pavement is dry. Yet depressions often reveal themselves following a rainstorm, since water will puddle up more prominently in such areas. Over time, such areas tend to develop cracks at a much faster rate, as the result of increased water exposure.

Depressions usually occur as the result of incomplete soil compaction. Over time, the soil beneath parts of the pavement shifts, leaving the asphalt without the necessary stability. Contractors can often fill in depressions with fresh asphalt, restoring the pavement to a proper level.

3. Shoving and Corrugation

Shoving involves the formation of a raised ridge on the surface of the asphalt. Shoving always occurs perpendicularly to the direction of traffic, whereas rutting occurs in a parallel direction. In some cases, shoving takes the form of multiple, ripple-like ridges - a phenomenon paving contractors distinguish with the name of corrugation.

Shoving occurs most frequently with unstable asphalt mixes, which do not have the necessary stiffness to stand up to stop and start traffic patterns. Corrugation often happens in areas such as traffic lights, where cars routinely stop and start. Shoving, by contrast, happens in areas where the asphalt directly abuts an immovable object.

Repair techniques vary depending on the extent of the distortion. Contractors can remove localized instances of shoving or corrugation and patch the area with fresh asphalt. Yet more widespread distortion may indicate general failure of the asphalt. In these situations, the solution often involves removing the entirety of the affected pavement and overlaying it with fresh asphalt.

Asphalt distortion alters the appearance, behavior, and lifespan of your pavement. Fortunately, you can avoid long-term problems by having a professional conduct and inspection and repair. For more information, please contact the paving experts at Metro Paving Company.



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