Prediction of permanent deformations in asphalt concrete using the mechanistic-empirical pavement design guide

University dissertation from Lunds universitet, instutionen för teknik och samhälle, trafik och väg

Abstract: Permanent deformations, or rutting, are internationally considered to be one of the most serious distress mechanisms in asphalt pavements. Deterioration modeling is an important tool for performance prediction and diagnostics of pavements. The Mechanistic-Empirical Pavement Design Guide (M-E PDG) model used for calculation of permanent deformation in asphalt layers was to be evaluated. It was accomplished by accelerated loading testing of two flexible pavements with the Heavy Vehicle Simulator (HVS), specimen production, laboratory testing of materials, and calculation of permanent deformations using the M-E PDG software v0.910. Field calibration factors were assessed in order to match the model’s results with the HVS results. It was also to be investigated whether the indirect tensile test (IDT) on cored pavement specimens can replace the compressive uniaxial test on gyratory compacted specimens for determination of dynamic moduli. This was carried out by comparing mastercurves from the uniaxial test on gyratory compacted specimens with those from the IDT on gyratory compacted specimens, which in turn were compared to mastercurves from the IDT using pavement cores. Results from the uncalibrated M-E PDG model underestimated the total permanent deformation in the asphalt layers but matched when a specific set of field calibration factors were used. The calibration factors found in this work increased the model’s temperature susceptibility and decreased its dependency on the number of passages. Regional field calibration factors can be assessed by employing a performance study of existing pavements. However, the model’s permanent deformation contribution of each layer to total rut depth did not correlate with HVS results in this investigation, and should therefore be refined with further trench studies on existing pavements. Contrary to expectation, mastercurves derived with the uniaxial test and the IDT using gyratory compacted specimens were not similar. Most importantly, they appeared to differ regarding dependency on frequency and temperature. The mastercurves from the IDT on gyratory compacted specimens and pavement cores were comparable.