Three-dimensional micromechanical finite element analysis on gauge length dependency of the dynamic modulus of asphalt mixtures

The dynamic modulus of asphalt mixture is one of the major parameters for pavement design. It is generally measured by gauge-point-mounted (GPM) measurement system based on indirect tensile test (IDT), which is very costly and time-consuming. Furthermore, the gauge length in the GPM system has a significant effect on the dynamic modulus but has not been taken into account. This paper focuses on the numerical simulation of the dynamic modulus of asphalt mixture and its dependency on gauge length. The microstructure of asphalt mixture was captured using the non-destructive X-ray computed tomography technique. The series of images were transformed into a three-dimensional (3D) data array that can be mapped into finite element method elements to build a 3D model. Meanwhile, the general Maxwell model was applied for viscoelastic mastic and calibrated from Prony series analysis of the mastic test data. The IDT numerical simulations by incorporating specimen microstructure and ingredient properties were conducted within linear viscoelastic range. The simulation results of the dynamic modulus have good correlations with the testing results. Moreover, the simulation shows the relationship between the dynamic modulus and gauge length. These results indicate that different gauge lengths affect the dynamic modulus significantly. Additionally, this study simulated the gauge length dependency of the dynamic modulus when considering viscoelasticity and heterogeneity.