What causes fatigue cracking in asphalt pavements?

Fatigue cracking in asphalt pavements primarily results from repeated bending and loading cycles. As vehicles travel over the pavement, the repeated stress from the weight of vehicles causes deformations in the asphalt layer. Over time, these repeated loads lead to the development of micro-cracks due to flexural fatigue, which can progressively enlarge and ultimately result in visible surface cracking.

This phenomenon is particularly noticeable in high-traffic areas where the frequency and weight of traffic exert a considerable amount of stress on the pavement structure. Engineers design asphalt mixes to withstand certain levels of this repeated loading, but if the pavement design or the materials used are inadequate, the fatigue cracking can occur sooner than expected.

Other factors, while still relevant to the overall performance and longevity of asphalt pavements, do not directly cause fatigue cracking in the same manner. For instance, excessive temperature fluctuations can affect the thermal stability and performance of the asphalt but are not the primary cause of fatigue cracking. Similarly, improper aggregate selection and insufficient binder content can impact the strength and durability of the pavement, but they may not directly relate to the fatigue failure caused by repetitive loading cycles.