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Load Cracking

Description:

This type of cracking is caused by repeated heavy loads and always occurs in the wheelpaths. This type cracking usually starts as single longitudinal cracks in the wheelpaths. As progression continues, short transverse cracks occur that intersect the original longitudinal cracks. Additional longitudinal cracks occur in the wheelpaths. As the number of longitudinal and transverse cracks in the wheelpaths increases, polygons are formed by the intersection of these cracks. As deterioration continues, these polygons become smaller (due to additional cracking) and, in the worse case, begin to pop out. When load cracking progresses to the point where small polygons are formed, rutting can become extensive and pumping of base material can occur.

Following are examples for each severity level of load cracking.

Load Cracking (Severity Level 1)

Level 1 Load Crack patterns are generally tight single longitudinal cracks in the wheelpaths. A wheelpath is approximately 3 feet wide and load cracking can occur at the edge of the wheelpath. Occasional short, tight longitudinal cracks parallel to the main longitudinal cracks can also occur and still be defined as level 1 load cracking pattern.

The illustration above is an example of the range in load cracking patterns to be recorded as level 1 load cracking. There is approximately 120 feet of cracking in the two wheelpaths or 60% of the sample in lane one in the two wheelpaths or 60% of the sample in lane one and 130 feet (65%) of level 1 load cracking in lane two.

Examples of Level 1 Load Cracking

Load Cracking (Severity Level 2)

The following illustration shows the general range in appearance of level 2 load cracking patterns. These cracks are wider than level 1cracks and occur only in the wheelpaths. This level cracking has a single or double longitudinal crack with a much larger number of 0-2 ft. transverse cracks intersecting than in level 1 load cracking. Occasionally polygons will form, but are not prominent.

In this example, there is approximately 150 ft. of cracking in the 100 ft. sample area, or 75% of sample area.

Examples of Level 2 Load Cracking

Load Cracking (Severity Level 3)

The illustration shows the general appearance of level 3 load cracking patterns. This type pattern generally has three or more longitudinal cracks in the wheelpaths with many interconnecting transverse cracks. Many small polygons are formed causing the appearance of “alligator hide”. This type cracking is marked by a definite, extensive pattern of small polygons and is sometimes accompanied by severe rutting.

In this example, 60% of the sample has level 3 load cracking.

Examples of Level 3 Load Cracking

Load Cracking (Severity Level 4)

The following illustration shows level 4 load cracking patterns. This type pattern has the definite “Alligator hide” pattern, but had deteriorated to the point that the small polygons are beginning to pop out. Rutting is usually severe and pumping of base material is sometimes evident.