TM 5-826-6/AFR 93-5
asphalt concrete (AC) surface under repeated traffic loading. The cracking initiates at the bottom of the AC surface (or
stabilized base) where tensile stress and strain are highest under a wheel load. The cracks propagate to the surface
initially as a series of parallel cracks. After repeated traffic loading, the cracks connect, forming many-sided, sharp-angled
pieces that develop a pattern resembling chicken wire or the skin of an alligator. The pieces are less than 2 feet on the
longest side.
b. Alligator cracking occurs only in areas subjected to repeated traffic loadings such as wheel paths.
Therefore, it would not occur over an entire area unless the entire area was subjected to traffic loading. Pattern-type
cracking, which occurs over an entire area that is not subjected to loading is rated as block cracking, which is not a load-
associated distress.
c. Alligator cracking is considered a major structural distress.
(2) Severity levels.
(a) Low severity level (L). Fine, longitudinal hairline cracks run parallel to one another with none or only a
few interconnecting cracks. The cracks are not spalled (figs. A-1 through A-3).
Figure A-1. Low severity alligator cracking, case 1.
Figure A-2. Low severity alligator cracking, case 2.
A-5
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