This study characterises the mechanical, rheological, induced heating, and induced healing behaviour of asphalt concrete containing steel wool fibers (SWFs) as the conductive constituent. Induced heating of asphalt concrete through the electromagnetic field is a novel method to heal the damage induced in asphalt concrete. Previous studies used high contents of the SWF as the conductive material to improve the sensitivity of the asphalt concrete to the electromagnetic radiations. Experimental tests conducted in this study (e.g. uniaxial strength, indirect tension, semi-circular bending tests) show that the addition of 0.2 (wt)% SWF meets both the heating and healing requirements. The relatively low amount of SWF resulted in considerably less adverse effects on the mechanical and rheological properties of asphalt concrete comparing to higher percentages of SWF (e.g. 1.5 (wt)% of SWF). Tests conducted on different specimen sizes of asphalt concrete reveal substantial effects of specimen dimension (volume) on the heating rate that should be considered in the evaluation of asphalt concrete induction heating under electromagnetic power. In addition, it is shown that using 0.2 (wt)% SWF significantly reduces the effect of corrosion on induced heating of conductive asphalt concrete materials. Experimental results demonstrate that the tensile strength ratio (TSR) decreases from 25% for 1.5% SWF to 7% for 0.2% SWF.

This paper proposes a straightforward procedure to characterize the nonlinear viscoelastic response of asphalt concrete materials. Furthermore, a model is proposed to estimate the nonlinear viscoelastic parameters as a function of the triaxiality ratio, which accounts for both confinement and deviatoric stress levels. The simplified procedure allows for easy characterization of linear viscoelastic (LVE) and nonlinear viscoelastic (NVE) responses. First, Schapery’s nonlinear viscoelastic model is used to represent the viscoelastic behavior. Dynamic modulus tests are performed to calibrate LVE properties. Repeated creep-recovery tests at variable deviatoric stress levels (RCRT-VS) were designed and conducted to calibrate the nonlinear viscoelastic properties of four types of mixtures used in the Federal Aviation Administration’s National Airport Pavement and Materials Research Center test sections. The RCRT-VS were conducted at 55°C, 140 kPa initial confinement pressure, and wide range of deviatoric stress levels; mimicking the stress levels induced in a pavement structure under traffic. Once calibrated, the model was validated by comparing the model predictions and experimental measurements at different deviatoric stress levels. The predictions indicate that the proposed method is capable of characterizing NVE response of asphalt concrete materials.

Three-dimensional (3D) microstructural representation of asphalt concrete subjected to moisture diffusion and mechanical loading is simulated and analysed. The continuum moisture–mechanical damage mechanics framework and the moisture damage constitutive relationship developed by the authors are used in this study to couple the detrimental effects of the mechanical loading and moisture diffusion on the complex response of asphalt concrete. A 3D finite element (FE) microstructural representation of a typical asphalt concrete is used for these simulations. The 3D microstructure is reconstructed from slices of two-dimensional X-ray computed tomography images that consist of the matrix and the aggregates. Results show that the generated 3D FE microstructure along with the coupled moisture–mechanical constitutive relationship can be effectively used to simulate the overall thermo-hygro-mechanical response of asphalt concrete. The analyses provide insight into the impact of the microstructure on the overall response of asphalt concrete.

Rutting performance of airfield pavements is predicted using mechanistic-based constitutive relationships for both asphalt and granular layers. Pavement analysis using nonlinear damage approach-airfield pavements (PANDA-AP) is used that encompasses a coupled viscoelastic–viscoplastic constitutive relationship to model the rutting distress in the asphalt layer and a modified extended Drucker-Prager-Cap (D-P-Cap) is used to predict permanent deformation induced in granular layers due to aircraft traffic. The D-P-Cap model captures the permanent deformation due to both shearing and densification of granular layers. Experimental test results from resilient modulus, cyclic triaxial, dynamic modulus, and flow number tests are used to fully calibrate the constitutive relationships. The calibrated constitutive relationship is then validated against independent lab experiments. The calibrated model is used to predict the performance of airfield pavement sections tested at the National Airfield Pavement Test Facility (NAPTF) of the Federal Administration Aviation (FAA). It is shown that the presented mechanistic-based constitutive relationships can be effectively used to predict the rutting performance of airfield pavements when subjected to high aircraft tire pressure.

The effect of different configurations of normal contact stresses on the rutting performance of asphalt concrete overlays on a soft and stiff Crushed Aggregate Base (CAB) layer is investigated. A three-dimensional (3-D) finite element model of a pavement structure is generated. The effect of different types of simplified normal contact stresses and a realistic 3-D normal stress on the rutting performance is investigated. Since the failure mechanism of asphaltic materials at high temperature is mainly related to the flow of the material, the viscoelastic and viscoplastic constitutive relationships coupled with the hardening-relaxation mechanisms are utilized to represent the behavior of asphalt concrete layer. This constitutive relationship is part of the PANDA (Pavement Analysis using Nonlinear Damage Approach) model developed by the authors and their collaborators. As the result of simulation, the magnitude of the rut depth on the asphalt concrete layer is generally determined to be inversely proportional to the stiffness of the CAB layer, and the rut depth on the asphalt concrete layer under the realistic 3-D normal stress is about 1.5 times greater than the rut depth under uniformly distributed normal stress.