This study investigates the effects of pavement interface conditions on hot-mix asphalt (HMA) overlay response using the laboratory and field measurements accompanied by a numerical analysis. A laboratory and accelerated testing programme were conducted as part of a comprehensive study to determine the optimum tack coat application rate for HMA–Portland cement concrete (PCC) composite pavements by Leng et al. (2008, Transportation Research Record: Journal of the Transportation Research Board, 2057, 46–53; 2009, Transportation Research Record: Journal of the Transportation Research Board, 2127, 20–28). This study synthesises the accelerated and laboratory test results with a 3D finite element (FE) model to evaluate the effects of various bonding conditions on the overlay response as well as the interface behaviour. The model outcome was validated using the laboratory and field results. The FE model was utilised to extend the findings of this study to different temperatures, tyre configurations and loading conditions. Pavement interface was modelled using a hyperbolic Mohr–Coulomb friction model, whereas HMA overlay was modelled as a viscoelastic material. A moving load was applied and implicit dynamic analysis was carried out. Field and laboratory experiments along with the numerical analysis proved the importance of achieving good bonding at the pavement interface for HMA overlay. This study found that as pavement temperature increases, the interface bonding effects on the overlay response are amplified. This could be the main contributing factor to overlay rutting. The influence of interface condition on the HMA surface and bottom strains was evaluated using a numerical model supported by full-scale accelerated pavement testing results. The effects of varying interface properties such as stiffness and strength on the HMA overlay response were investigated. The numerical model provided a range of expected HMA critical strains under realistic interface conditions ranging from full bonded to debonded conditions. This study clearly shows the significance of tack coat type and application rate effects on pavement critical responses through laboratory, in-situ response and advanced modelling.

Cracking in asphalt concrete (AC) layers is among the driving modes of flexible pavement deterioration. Material properties, along with structural layer characteristics and external factors such as vehicular and environmental loading, govern cracking mechanisms in flexible pavements. Current practice of AC and pavement structural design methods does not allow for direct characterisation of AC impact on crack damage initiation and propagation. Asphalt concrete performance tests are the essential components of performance-related and performance-based specifications, for which they can be used either for screening AC to minimise deterioration risks or to directly predict specific modes of pavement deterioration. This paper evaluates commonly used performance tests intended to characterise AC fracture resistance. A multi-step evaluation protocol was applied using various statistical techniques to determine the discrimination ability of each test method outcome criterion as well as strength of correlation to field performance. The results from full-scale accelerated pavement test (APT) sections were used to correlate with the results obtained from various laboratory performance tests. Mixes used in the study contained various levels of reclaimed asphalt pavement and recycled asphalt shingles with a recycled binder ratio up to 40%. It was shown that the flexibility index parameter obtained from the Illinois semi-circular bending (IL-SCB) test, also referred to as the Illinois Flexibility Index Test (I-FIT), resulted in the highest number of subsets and consistent ranking with APT field performance, indicating a high discrimination potential. Even though two of the overlay test’s criteria resulted in fewer subsets, they also provided a consistent ranking with APT field performance. Composite scores indicate that the overlay test criteria and flexibility index from the I-FIT had the highest strength of correlation to field performance.

A three-dimensional finite element model was developed to investigate the fracture behavior of a hot-mix asphalt (HMA) overlay on a jointed concrete pavement (JCP). Moving vehicular loads were applied to the HMA overlay on top of a joint to develop reflective cracking. A bilinear cohesive zone model (CZM) was inserted in the HMA overlay right over the joint. An interface constitutive model was implemented to specify interfacial behaviors between HMA-concrete layers. This study primarily examined the effects of interface bonding conditions on reflective cracking. The local and global behaviors of reflective cracking were investigated under various interface conditions regarding interfacial stiffness and bonding strength. Reflective cracking potential is quantified with representative fracture area (RFA), which represents a fractured area in the cross section of the HMA overlay. As a result, the fractured area increases significantly as the interface bonding strength becomes lower. On the contrary, the fractured area decreases slightly as the interface stiffness becomes lower.

In this paper, the mechanism of near-surface cracking under critical loading conditions was investigated using mechanistic modeling approaches. These loading conditions were represented by a combination of nonuniform tire contact stresses in three directions generated during vehicle maneuvers (free rolling, acceleration/braking, and cornering) that were predicted from a tire-pavement interaction model. Three-dimensional finite element models of uncracked and cracked pavements were developed to evaluate the critical factors that are responsible for crack initiation and propagation at the near-surface of a typical full-depth pavement structure. It was found that the near-surface cracks in the proximity of tire edges showed strong mixed-mode (tension and shear) fracture potential. The pavement responses from both uncracked and cracked pavement models indicated that shear mode of fracture in the presence of compression appeared to be the dominant mode of damage for near-surface cracking. Compared to t...