Causes, Mechanisms, and Remedies of Top-Down Cracking of Asphalt Pavements: State-of-the-Art

One of the major distresses affecting the service life of asphalt pavements is the phenomenon known as Top-Down Cracking (TDC). A literature review was conducted of the current and previous efforts invested in the field. The study addresses the initiation, progression mechanisms, causes, and the applied remedies to the problem of TDC. It is demonstrated that thermal analytical models which have been used in the literature over the past decades failed to explain the main cause of thermal transverse cracking. Moreover, the study showed that load-induced tensile stresses and strains are not the sole cause of TDCs. It has been shown that the current compaction methods and techniques continue to be the most predominant cause of TDC. Additionally, analysis performed in this thesis attempted to identify the promising techniques to mitigate TDC. While these techniques were developed, the most effective current approach appears to be a new compaction technology termed "AMIR". The research also included laboratory investigation to assess the influence of TDC on the environmental performance and on the integrity of the asphalt concrete layer. Results of laboratory tests suggested that top-down-cracks can lead to serious environmental problems related to pollution agents interacting with the cracked pavement leading to significant loss of its mechanical properties and adverse effects on the environment.