What does the term "fatigue cracking" refer to in asphalt pavements?

Fatigue cracking in asphalt pavements specifically refers to cracks that develop due to the repeated loading and unloading cycles experienced by the pavement. As vehicles travel over the asphalt, the repeated stresses cause fatigue in the pavement material, leading to the formation of cracks. Over time, these cracks can expand and propagate further, especially under conditions where the asphalt is unable to adequately resist tensile stresses.

Understanding the underlying mechanics of fatigue cracking is crucial for pavement design and maintenance. Engineers aim to create asphalt mixtures and pavement structures that can withstand expected traffic loads and mitigate the effects of stress over time.

The other choices pertain to different failure mechanisms. For example, moisture infiltration can lead to stripping or other types of damage but is not the same as fatigue cracking. Similarly, UV exposure affects the surface and can lead to degradation, and thermal expansion relates to temperature changes but does not denote issues caused by repetitive loading. Each type of distress has its own causes and implications, highlighting the importance of accurate identification in asphalt pavement management.