Permanent deformation is one of the dominant asphalt concrete damages. Significant progress has been made to realistically predict the damage. In the last decade, the mechanistic approach has been the focus of research, and the fundamental theories of viscoelasticity, viscoplasticity, continuum mechanics, and micromechanics are applied to develop the material laws (constitutive equations). This paper reviews the advancement of permanent deformation models including analogical, microstructural, and continuum-based methods. Pavement analysis using the nonlinear damage approach (PANDA) is the most comprehensive and theoretically sound approach that is available in the literature. The model coupled different damages and other phenomena (such as cracking, moisture, and phenomena such as healing, aging, etc.). The anisotropic microstructure approach can be incorporated into the PANDA approach for a more realistic prediction. Moreover, the interaction of fatigue and permanent deformation is the gap that is lacking in the literature. The mechanistic approaches have the capacity to couple these damages for unified asphalt concrete damage prediction.

The linear viscoelastic (LVE) properties of asphalt concrete is investigated in this paper using a controlled-strain triaxial dynamic modulus test over wide frequency, temperature, and confining pressure ranges. The time–temperature-pressure superposition principle (TTPSP) is applied to validate the thermo-piezo-rheological simplicity of the tested materials using triaxial master curves. The LVE response is found highly stress-dependent at intermediate and high temperatures. The Prony series modeling of time-domain properties ascertains that confining pressure strongly correlates with long-term relaxation modulus, the absolute maximum slope of the relaxation modulus, and viscoelastic damage parameter. The stress triaxiality ratio concept is applied, and a new shift model is proposed that takes the triaxiality ratio as an internal state variable in the TTPSP. The model prediction agrees well with the experimental data. Moreover, a relationship between the long-term relaxation modulus and the triaxiality ratio is established. The triaxiality ratio coupled with TTPSP can accurately describe the stress-dependent response of asphalt concrete in the LVE domain.

One of the traffic calming devices used in Addis Ababa, Ethiopia is a speed hump due to low cost and ease of installation. However, these speed humps are randomly placed without proper engineering studies and justification. Due to this, speed fluctuations and the excessive decelerations and accelerations, before and after speed humps, over small distances and infiltration of water to the pavement surface. The pavement condition near to the speed humps show failure and deterioration. The research study was initiated to investigate the effect of speed humps on pavement condition and also to analyze the relationship between speed hump characteristics and pavement condition. The research methodology involved selecting representative samples of road segments that have at least one section with speed humps. For the selected section pavement condition and IRI data collected from AACRA. Road and speed hump characteristics data collected from site direct measurement. Collected data analyzed and compare the pavement condition of these sections with and without speed hump. Regression analysis models were developed to represent the relationships between pavement conditions and hump characteristics. Pothole and Raveling were the most widely observed distress at both sections with and without speed hump. But their frequency was higher on sections with speed humps. Pavement condition index (PCI), in road sections with and without speed hump, was calculated from the pavement condition data. The analysis showed that the presence of speed humps significantly affected the pavement condition, reducing the PCI of the pavement sections by 34 PCI points and increase IRI value by 3.4 IRI points. The relation between speed hump characteristics and pavement condition show that the speed hump height and density have a negative relation to pavement condition index value and speed hump width have positive relations with PCI value.