Evaluation of Field Transverse Cracking of Asphalt Pavements
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Transverse cracking is one of the major distress types in asphalt pavement. The crack initiates from pavement surface and propagates downward (thermal cracking), or initiates from pavement bottom and propagates upward (reflective cracking). In this study, the mechanism and key factors of a transverse cracking type named Surface-initiated reflective cracking (SIRC) are identified and evaluated. SIRC refers to crack that initiates at the surface of pavement layer in transverse direction and propagates downward to match the existing transverse cracking, and there is no cracking in the interlayer. The mechanism and key factors of the SIRC are evaluated by using three-dimensional Finite Element Method and laboratory modified Hamburg Wheel Tracking Test. Results indicate that when the HMA surface layer is thick, thermal load associated with traffic load, overlay stiffness and thickness above existing crack/joint are the key factors to initiate SIRC. When the pavement thickness is at certain thickness range (i.e., thick enough to protect the existing crack/joint to move but not too thick which can allow the surface layer bending downward with weak base structure), with relative stiff overlay material and weak base, tensile stress can develop at the surface of the pavement layer which can ultimate lead to SIRC under repeated traffic load. The widely used transverse cracking prediction model TCMODEL is evaluated to check its predictive quality on conventional transverse cracking and the SIRC. It is found that the predicted transverse crack from TCMODEL do not match well with the field measurements and therefore, it is necessary to develop new predictive models for transverse cracking including all transverse cracking types. Statistical methods in conjunction with engineering interpretation is used to develop crack initiation and propagation models for both SIRC and conventional transverse cracking. Hour of low temperature (<15°F), percent passing #200 sieve, IDT strength and service life (age) are found to be the critical indicators for the initiation of the transverse cracking. Material properties (mixture creep compliance, work density, and percent passing #200 sieve), pavement structure (overlay thickness), climate (hour of low temperature), and traffic (AADTT) are found to be critical factors for the propagation of the transverse cracking.