Ravelling: Causes, Consequences, and Cures
Maintaining road quality is essential for ensuring safe and smooth travel. One common issue that affects asphalt pavements is ravelling, a process that can significantly degrade the driving experience and safety of a road. In this blog, we delve into the details of ravelling—what it is, why it occurs, and how to address it effectively.
What is Ravelling?
Ravelling is the disintegration of an asphalt road surface due to the dislodgment of aggregate materials (gravel, sand, and crushed stone). This reduces skid resistance, roughens the road surface, and exposes the layers underneath to further deterioration. Additionally, ravelling results in loose gravel, which can be hazardous for vehicles. Imagine the sound of Pop Rocks crackling on your tongue—that's similar to the noise your car makes when driving over a ravelled road.
Why Ravelling Occurs
Several factors contribute to ravelling, including:
Age: As asphalt pavements age, the asphalt binder hardens, leading to ravelling.
Traffic: High traffic areas, especially those with heavy truck traffic, experience more wear and tear, increasing the likelihood of ravelling.
Poor Aggregate Mix: An improper balance of different-sized rocks in the asphalt mix can lead to air gaps and weak packing structures. Fine particles, like sand, are essential for a solid packing structure. The mix ratios should be tailored to the local climate and expected traffic loads.
Poor Compaction: Adequate compaction ensures high-density pavements. Without proper compaction, the aggregate won't bond well with the binder. Asphalt should be compacted at temperatures of at least 290℉ to ensure proper binding.
Dust: Accumulated dust causes the binder to adhere to the dust instead of the aggregate, weakening the bond and accelerating deterioration with vehicular traffic.
Moisture: The presence of moisture during paving renders the binder ineffective in adhering to the aggregate.
How to Fix Ravelling
To fix ravelling, follow these steps:
Assess the Pavement: Determine the severity of the damage.
Repair the Pavement: Based on the type of damage, apply the appropriate fix:
Low Severity Ravelling (Localised): Remove the ravelled area and patch it.
High Severity Ravelling (Widespread): Remove the damaged area and apply an overlay.
Prevention is Essential
Prevention is crucial to maintaining road quality. Here are some preventative measures:
Use high-quality binder and a balanced mix of aggregates suited for local weather conditions when constructing new roads. Different climates and regions require specially formulated aggregates and binder content for optimal performance and longevity.
Apply a preventative sealant layer based on traffic volumes. Options include fog seals, seal coats, micro-surfacing, or thin overlays of hot-mix asphalt (HMA Thin Overlay).
Regularly clean the streets. Maintenance is a cost-effective way to prevent ravelling and extend the life of the pavement.
How PMS Identifies Ravelling
PMS uses the LCMS-2 which provides the following advantages to identifying ravelling:
Accuracy: 3D data provides a more precise picture of the pavement surface, allowing for better detection of ravelling compared to visual inspection.
Objectivity: Algorithms remove subjectivity from the assessment, providing consistent and repeatable results.
Consider the powerful LCMS-2 in your road assessments to make sure that your data is accurate and objective. For more information, click here to download the free technical brochure.
Conclusion
Ravelling, the breakdown of asphalt roads, can cause rough surfaces and hazardous driving conditions. Understanding its causes, like aging, heavy traffic, poor asphalt mix, and moisture, helps us prevent and fix it effectively. Regularly assessing road conditions and using quality materials for repairs can reduce ravelling. Preventive steps, such as applying sealants and keeping roads clean, also help maintain road quality. Advanced tools like the LCMS-2 provide accurate and reliable road assessments. By focusing on these practices, we can ensure safer and smoother roads for everyone.