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Pavement Management
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Stripping

Description

The loss of bond between aggregates and asphalt binder that typically begins at the bottom of the HMA layer and progresses upward. When stripping begins at the surface and progresses downward it is usually called raveling.

Although the displacement of asphalt on the aggregate particle surface by water (stripping) is a complex phenomena and is not yet fully understood, mineralogy and chemical composition of the aggregate have been established as important contributing factors (Roberts et al., 1996[1]). In general, some aggregates have an affinity for water over asphalt (hydrophilic). These aggregates tend to be acidic and suffer from stripping after exposure to water. On the other hand, some aggregates have an affinity for asphalt over water (hydrophobic). These aggregates tend to be basic and do not suffer from stripping problems. Additionally, an aggregate’s surface charge when in contact with water will affect its adhesion to asphalt cement and its susceptibility to moisture damage. In sum, aggregate surface chemistry seems to be an important factor in stripping. However, specific cause-effect relationships are still being established.

Figure 1: Core hole showing stripping at the bottom.

Figure 2: Core hole showing stripping at the bottom.

Figure 3: Fatigue cracking caused by stripping at the bottom HMA.

Problem

Decreased structural support, rutting, shoving/corrugations, raveling, or cracking (fatigue and longitudinal)

Possible Causes

Bottom-up stripping is very difficult to recognize because it manifests itself on the pavement surface as other forms of distress including rutting, shoving/corrugations, raveling, or cracking. Typically, a core must be taken to positively identify stripping as a pavement distress.

Repair

A stripped pavement should be investigated to determine the root cause of failure (i.e., how did the moisture get in?). Generally, the stripped pavement needs to be removed and replaced after correction of any subsurface drainage issues.



Footnotes    (↵ returns to text)
  1. Hot Mix Asphalt Materials, Mixture Design, and Construction.  National Asphalt Paving Association Education Foundation.  Lanham, MD.

 

 

 

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Thanks for sharing Stripping.