Block cracks are interconnected cracks that divide the pavement into approximately rectangular pieces. The blocks may range in size from approximately 1 by 1 ft (0.3 by 0.3 m) to 10 by 10 ft (3 by 3 m). Block cracking is mainly caused by shrinkage of the asphalt concrete and daily temperature cycling, and it is not load associated. The occurrence of block cracking usually indicates that the asphalt has hardened significantly. Block cracking normally occurs over a large portion of pavement area.
|Low||Blocks are defined by cracks that are non-spalled (sides of the crack are vertical) or lightly spalled, causing no foreign object damage (FOD) potential. Non-filled cracks have a 1/4 in (6 mm) or less mean width, and filled cracks have filler in satisfactory condition.|
|Medium||The blocks are defined by one of the following: (1) filled or non-filled cracks that are moderately spalled (some FOD potential); (2) non-filled cracks that are not spalled or have only minor spalling (some FOD potential), but have a mean width greater than 1/4 in (6 mm); (3) filled cracks with a mean width greater than 1/4 in (6 mm) that are not spalled or have only minor spalling (some FOD potential), but have filler in unsatisfactory condition.|
|High||Blocks are well defined by cracks that are severely spalled, causing a definite FOD potential.|