Which of the following is NOT true about the cause of alligator cracking?

• A. Increase in loading
• B. Decrease in pavement support
• C. Subgrade swelling
• D. Inadequate compaction

Answer: (C)

Alligator cracking, also known as fatigue cracking, typically occurs in pavement surfaces due to repeated loading and is characterized by a series of interconnected cracks that resemble the skin of an alligator. The causes of alligator cracking are primarily related to factors that directly affect how the pavement bears loads and its structural integrity.

The correct answer indicates that subgrade swelling is not a recognized cause of alligator cracking. Subgrade swelling usually occurs due to moisture changes in expansive soils and can lead to other types of distress in pavements, such as heaving or cracking. However, it does not directly contribute to the formation of alligator cracking, which is more closely linked to load-induced stress and inadequate support conditions.

Increasing load and decreased pavement support can definitely lead to alligator cracking, as both factors increase strain on the pavement surface. Inadequate compaction during the initial installation of the pavement can create voids and weak spots, compromising its structural capability and leading to stress concentrations that promote cracking. Therefore, it is crucial to ensure proper compaction to maintain the pavement's integrity under traffic loads.