16 REFLECTIVE CRACKING Reflective cracking is a type of asphalt pavement failure that occurs when cracks appear in a flexible overlay over an existing crack or joint in the underlying surface. Reflective cracking occurs when a new layer of asphalt is placed over an old layer of asphalt, there is movement (such as thermal expansion/contraction) of the asphalt, and cracks develop at weak points in the pavement section, which is where there are already cracks in the old layer of asphalt. • The same effect can occur when asphalt is placed over joints or edges of concrete. • The effect is exacerbated as asphalt hardens over time. To prevent reflective cracking, you can: • Use thicker overlays to help dissipate stresses and reduce the severity of cracks. • Rubblize or heavily fracture concrete pavement before overlaying it with asphalt pavement. • Use geogrids, geocomposites and geogrid composites between the old asphalt and the overlay to delay the onset of reflective cracking and reduce the magnitude and severity of cracks. • In warm climates, incorporating fabric under a chip seal can improve the life of a chip seal by 50-70%. Tips on responding to reflective cracking: • Fill cracks soon after they appear. • New asphalt can be saw-cut to form a clean opening and filled with mastic to control the location of cracking.
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