Evaluation of deformation response of HMA under APT and wheel tracking tests

South Africa has experienced rapid economic growth in recent years. As a result the freight traffic on the country’s roads has increased steeply. In the same time the legal axle load for trucks has increased and so did truck tire pressures. This combination of factors places high demands on the country’s road network. Existing local Hot-Mix Asphalt (HMA) design guidelines were found lacking in light of this new reality by industry stakeholders. More reliable design procedures are required to combat premature rutting (especially at intersections) and fatigue cracking of HMA surfacing. Thus, under the auspices of the Gauteng Department of Public Transport, Roads and Works, a research project was started to update HMA design methods. This paper is based on a study into the rutting performance of HMA which forms part of the larger research initiative. The aim of this phase is to identify and develop appropriate test protocols and associated acceptance criteria for the assessment of rut resistance of HMA. A road test section, surfaced with a standard continuously graded medium HMA material, was subjected to full scale Heavy Vehicle Simulator (HVS) and scaled Model Mobile Load Simulator (MMLS) testing. A laboratory test program to characterize the material was also conducted. This paper contains a comparison between the Accelerated Pavement Testing in the field and wheel tracking tests performed as part of the laboratory study (Hamburg Wheel Tracking Tests and Transportek Wheel Tracking Test). The method of analysis of the creep curves is presented as well as the method used for comparing measured permanent deformation with mechanistically determined elastic strain values. The average elastic shear strain at the edge of the tire over the full thickness of the HMA layer was found to be the best indicator of plastic deformation potential at different temperatures.