What is the major cause of raveling?

The major cause of raveling in asphalt pavements is the loss of binder from the pavement surface, leading to the dislodging of aggregate particles. This loss of binder can be caused by a variety of factors, including oxidation of the asphalt binder, inadequate asphalt content in the mix, poor aggregate gradation, inadequate compaction during construction, and stripping (loss of adhesion between the asphalt binder and the aggregate). As the binder deteriorates or is lost, the aggregate particles become less tightly held together and are more easily dislodged by traffic. This process typically begins with the loss of fine aggregate particles and progresses to the loss of larger particles as the binder continues to deteriorate. Raveling can lead to a rough and uneven pavement surface, reduced skid resistance, and increased noise levels. It can also accelerate the deterioration of the pavement by allowing water to enter and damage the underlying layers. Therefore, proper mix design, construction practices, and maintenance are essential for preventing raveling.