Development of finite element model based on indirect tensile test for various asphalt mixtures

The Finite Element (FE) method allows for use of advanced material models and an effective and adequate analysis of mechanical behaviours for flexible pavements. This study aimed to validate the FE modelling of four types of asphalt mixtures considering the stress and strain responses derived from Cyclic Indirect Tensile Test (CITT). This research investigated the influence of asphalt surface layers with thicknesses of 40, 60, 80, 100, 120, 140 and 160 mm on the stress and strain at the bottom of asphalt surface and base layers. The viscoelastic behaviour of the material was described by the generalised Maxwell model using the Prony series method. The relaxation modulus was converted from the master curve constructed from the CITT results. The tensile stresses of the numerical models matched the measured values, showing a high Coefficient of Determination (R2 > 0.96) and low Mean Absolute Percentage Errors (MAPE & AP; 10%). In contrast, the fitting of tensile strain was better at reduced frequencies higher than 100 Hz representing the low temperature (high frequency) conditions. It was also found that a surface layer having a thickness up to 100 mm significantly reduced stress and strain at the bottom of both the asphalt surface and base layers. Asphalt mixtures with larger dynamic modulus showed smaller stress responses at the bottom of the asphalt layers under the same vehicle load. The tensile strain at the interface between courses highly depended on the stiffer layer. The experimental compressive stress and strain values showed a linear correlation with the tensile stress and strain evaluated in the FE model. After validating the constitutive relationships implemented in the FE approach against the experimental CITT results, the nu-merical model incorporating the master curve developed in this study was a very useful tool to predict the stress and strain responses of flexible road pavements.