Calibrating and Validating Overlay Tester–Based Fatigue Cracking Model with Data from National Center for Asphalt Technology

There is a national movement to develop mechanistic–empirical methods for the design of flexible pavements, for which fatigue cracking is a major distress mode. Fatigue cracking has been studied for several decades. Different types of fatigue cracking models have been proposed. After a review of existing fatigue cracking models in the literature, it was found that the overlay tester–based fatigue cracking model was a rational choice for predicting the development of fatigue cracking and for incorporation into the mechanistic–empirical design system. The main features of the overlay tester–based fatigue cracking model include incorporation of both crack initiation and crack propagation stages; involvement of fracture properties (i.e., A and n) of every asphalt layer, if the flexible pavement has multiple asphalt layers and each layer material is different; and use of the simple overlay tester for determining the fracture properties required for predicting both crack propagation and crack initiation. The proposed fatigue cracking model was preliminarily calibrated with material properties and fatigue cracking performance data from seven test sections evaluated in the 2006 test cycle at the National Center for Asphalt Technology's Pavement Test Track. Validation of the calibrated model was performed with performance data from the 2003 test sections at the National Center for Asphalt Technology Pavement Test Track. Thus far, satisfactory results have been obtained. However, further model validation and calibration with more field data, varied traffic load spectra, different environmental conditions, and different materials are still required.