Possible role of thermal ratchetting in alligator cracking of asphalt pavements

Although recognised as contributing to certain forms of crack development in asphalt, thermal effects are rarely seen as the primary cause of perhaps the most prevalent forms of crack pattern. This technical note will argue that far from just contributing, thermal effects might often provide the initiating and propagation mechanism for the evolution of many classes of crack pattern. It will suggest that restrained expansion and contraction during alternations in heating and cooling often result in forms of cracking which are not fully recovered at the end of each thermal cycle. It is argued that this could provide an alternative explanation for certain forms of top-down cracking and especially those referred to as 'alligator cracking'. It is further suggested that greater recognition of the thermo-mechanical processes, thought to be responsible for various types of pavement cracking, might have important implications for improving future pavement design and maintenance strategies.