20 Raveling can be caused by problems related to the mix design, construction, or environmental effects, including: • Insufficient binder in the asphalt mix. • Asphalt being mixed with dirty aggregate, to which the binder in the mix cannot properly adhere. • Segregation of the aggregate in the mix prior to being laid. • Inadequate compaction of the asphalt layer. • Breakdown of the binder over time or due to exposure to solvents (such as gasoline or engine oil) and erosion of fine aggregate. To prevent raveling, you can: • Follow design and construction best practices. • Prevent exposure to solvents that would break down the binder in asphalt pavement. Tips on responding to raveling: • Before putting a treatment over raveled asphalt, clean all loose pieces of asphalt and aggregate from the old asphalt. ASPHALT RAVELING Asphalt raveling is the process by which the top layer of asphalt breaks down, exposing the aggregate materials underneath, such as gravel, sand and crushed stone, and making a road surface rough and pitted. It can also compromise the foundation of the asphalt, making the surface more vulnerable to further deterioration. Raveling is one of the most common issues with driveways and parking lots, but it’s also one of the most easily repairable.
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