What is it?
Reflective cracking occurs when breaks or cracks in the underlying layers become visible on the asphalt surface through a patch, overlay, or seal coat. The original cracks can be caused by several factors (age hardening, temperature cycling, separation of underlying joints, shrinkage of the subgrade, extensive water damage, excess pressure, asphalt applied too thinly, etc.) and will eventually appear on the asphalt surface if merely covered rather than being completely removed and replaced.
How do you fix it?
Long story short, you don’t. Reflective cracking will remain hidden under a patch, overlay, or seal coat for a while, but the cracks will always make their way back to the surface. Cracks can reappear in as little as a few months, but generally will stay hidden for about 1 year per inch of asphalt overlay although this isn’t an exact science and will vary greatly depending on factors such as: environmental conditions, amount and depth of cracks, wear and tear, etc. Patching, overlays, and crack seal with seal coat will help prevent further water penetration and damage to your asphalt and subgrade, but they’re not a long-term solution to your cracking issues. The only true “fix” would be to cut out the damaged area, take it down to the subgrade by removing all the damaged asphalt, and repave the area.