ALLIGATOR CRACKING

Note: The entire lane in one direction of travel on a two- lane facility represents 50% of the section.

Light:Longitudinal disconnected hairline cracks about 1/8 inch wide running parallel to each other; initially may be only a single crack in the wheel path but could also look like an alligator pattern; sealant is satisfactory for sealed cracks.

Moderate: Longitudinal cracks in wheel path(s) forming an alligator pattern; cracks may be lightly spalled are about 1/4 inch wide.

Severe: Cracking has progressed so that pieces appear loose with severely spalled edges; cracks are probably 3/8 -1/2 inch wide or greater; pumping of fines through the cracks may be visible on the pavement surface; potholes may be present.

Description:

Alligator cracking is a load associated structural failure. The failure can be either in the surface, base or subbase. Permanent deformation (rutting) does not have to be present for there to be alligator cracking.

Cracking first begins in the wheel path, usually as longitudinal cracking. Further stress creates an alligator pattern. If the surface is very flexible the longitudinal crack will become wider and an alligator pattern may not develop until severe distress sets in. The proper solution for both alligator and longitudinal cracking is the same since a structural failure is taking place in both cases.Alligator cracking will also include cracking along the pavement edge.

Each lane of a two-lane facility is to be evaluated as representing 50% of the section. For example, if there is continuous moderate alligator cracking in either one or both wheel paths of one lane only, the rater should mark 50% under moderate alligator cracking. If similar cracking had been present in the other lane, the rater would mark 100% under moderate.

For multi-lane undivided facilities the total number of lanes shall be divided into 100 to yield the percentage that each lane represents. For example, each lane of a five-lane facility would represent 20% of the section.

Construction joints are not rated unless the pavement in that area has begun to fail or show distress.

For multi-lane undivided facilities only the outside lane (or most distressed lane) in each direction shall be rated. These lanes will be rated together as one direction.

For sections where the alligator, longitudinal or transverse cracking has been sealed, the rater should rate the severity of the crack, to the best of his or her ability, regardless of the sealant. This is necessary to pick up the fact that the section may have moderate or severe cracking and not to penalized for sealing the cracks.

Sections with scattered potholes are difficult to evaluate. Potholes represent spot locations of severe cracking. If no other alligator cracking is present, then seldom do the potholes add up to 10%. So, for those sections that have about 5-10 potholes per mile with no other alligator cracking, the rater should mark 10% (01) under moderate.

* Important change in Alligator Cracking

The new pavement condition survey will rate all edge cracking as alligator cracking.

Edge cracking is alligator cracking except it is usually located within 1 - 2 feet of the edge of the pavement. Edge cracking pinpoints an edge failure rather than a lane failure, as in alligator cracking. The failure begins at the edge of the pavement and progresses in towards the center of the lane.

It is important to note edge cracking as it is an indicator that the edge may need strengthening either by PM patching, full-depth patching, and/or widening. Certainly, ponding of water at the pavement edge can contribute to and worsen an existing edge failure. By saturating the base, the strength at the edge is further reduced which increases the rate of deterioration of the pavement.

1. ALLIGATOR CRACKING (Edge)

Light: Hairline cracks just beginning to show; are random with no pattern; cracks may be 1/8 inch wide.

Moderate: Cracks more extensive and may be forming an alligator pattern; cracks are about 1/4 inch wide may be spalled.

Severe: Cracks are alligatored and severely spalled; cracks usually 3/8 - 1/2 inch wide or greater; pieces may be loose and potholes may be present.

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