Distress Call: Raveling!

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It can be hard to distinguish between the many road distresses unless you’re an engineer or construction specialist. Our series, Distress Call, will help you identify between the various classes of distresses. Today, let’s talk about raveling.

Raveling is the disintegration of an asphalt road surface. It is due to the dislodgment of the aggregate materials (gravel, sand, and crushed stone). It reduces skid resistance, roughens the road surface, and exposes the layers underneath to further deterioration. Raveling also results in loose gravel that can be dangerous for your vehicles. Remember Pop Rocks? Driving over a raveled road will sound similar to the candy crackling on your tongue.

Example of road distress, Raveling
Example of a disintegrated asphalt road.

How it Happens

  • Age: Asphalt pavements ravel when the asphalt binder ages and hardens.
  • Traffic: It occurs commonly in high traffic areas due to wear and tear. If there is a lot of truck traffic (heavier loads), the chances of raveling are even higher.
  • Poor Aggregate Mix: The asphalt mix should have a proper balance of different sized rocks, to ensure that it packs well, without forming air gaps. Fine particles, like sand, are a crucial component because it produces a solid packing structure. The mix ratios should be calculated based on the local climate and expected traffic loads.
  • Poor Compaction: Good pavements have high density, which requires adequate compaction. Without proper compaction, the aggregate will not bond well with the binder. Asphalt should be compacted at higher temperatures (a minimum of 290℉ or higher) to ensure proper binding.
  • Dust: Accumulation of dust causes the binder to adhere to the dust, which will ultimately weaken the aggregate bonding. Deterioration accelerates with vehicular traffic.
  • Moisture: The presence of moisture during paving makes the binder ineffective at adhering to the aggregate. Moisture + Pavement=Bad.

How to Fix Raveling

First, you will need to assess the pavement, and second, repair depending on the type of damage. Simple, right?

  • For low severity raveling (localized): Remove raveled area and then patch.
  • For high severity raveling (widespread): Remove damaged area and apply an overlay.
localized raveling
Image above, left: extreme localized raveling. On the right: widespread raveling

Prevention is Your Best Friend

Keep this in mind, what matters most is prevention.

When constructing new roads, choose a high-quality binder and a balanced mix of aggregates recommended for local weather conditions. Different climates and regions require specially formulated aggregates and binder content to allow pavements to function optimally and last longer without wearing down. Use a preventative sealant layer based on traffic volumes. This could be a fog seal, a seal coat, micro-surfacing, or a thin overlay of hot-mix asphalt (HMA Thin Overlay).

And finally, the simplest and most cost-effective way to prevent raveling is to keep the streets clean. Maintenance goes a long way, so keep this in mind as you go forward with your road assessments.

With RoadBotics, you can see all of your roads on our online platform, RoadWay. By having images of your entire road network, you can easily monitor every distress and prevent further deterioration. If you are interested in learning more, start your free demo today!

Article adapted from Everything Roads. Original title ‘Know Thy Enemy’ written by RoadBotics current Director of Product and CX, Nikhil Ranga.

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