TM 5-826-6/AFR 93-5
(2) Severity levels. No degrees of severity are defined. Bleeding should be noted when it is extensive enough
to cause a reduction in skid resistance (figs A-7).
Figure A-7. Bleeding.
c. Block cracking, distress 43.
(1) Description. Block cracks are interconnected cracks that divide the pavement into approximately
rectangular pieces. The blocks may range in size from approximately 1 by 1 foot to 10 by 10 feet. When the blocks are
larger than 10 by 10 feet, they are classified as longitudinal or transverse cracking. Block cracking is caused mainly by
shrinkage of the asphalt concrete and daily temperature cycling (which results in daily stress/strain cycling). 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 the pavement area, but sometimes it will occur only in nontraffic areas. This type of
distress differs from alligator cracking in that the alligator cracks form smaller, many-sided pieces with sharp angles. Also
unlike block cracks, alligator cracks are caused by repeated traffic loadings and are, therefore, located only in traffic areas
(i.e., wheel paths).
(2) Severity levels.
(a) Low severity level (L). Blocks are defined by cracks that are nonspalled (sides of the crack are
vertical) or only lightly spalled with no loose particles, causing no foreign object damage (FOD) potential. Nonfilled cracks
have 1/4 inch or less mean width, and filled cracks have a filler in satisfactory condition (figs. A-8 through A-10).
A-8
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