Abstract
Constant strain rate tests for a graded asphalt mixture under three constant strain rates have been undertaken in the laboratory. The Discrete Element Model has been used to simulate the laboratory tests with a numerical sample preparation procedure being developed to represent the physical specimen. The Burger’s model has been used to represent the time dependent behavior of the asphalt mixture. The Burger’s model was implemented to give bending and torsional resistance as well as in direct tension and compression. The stress-strain response for the laboratory tests and the simulations under three loading speeds were recorded. The results show reasonable agreement when the bond strengths in the model are made to be a function of strain rate. Both normal and Weibull distributions have been used for the bond strengths between the aggregate particles. The effects on the stress-strain response of bond strength variability and particle position are proved to be negligible. Bond breakage was recorded during the simulations to explain the internal damage within the sample. The modified Burger’s model has proved to be a useful tool in modeling the bending and torsional resistance at particle contacts in an asphalt mixture, in order to correctly predict observed behavior.
Highlights
The traditional approach to model asphaltic materials is to treat them at the macro-scale using continuum-based models which are implemented into a finite element program
An alternative approach is to use the Discrete Element Method (DEM), which has been widely used to model the behavior of granular materials, in order to gain micro-mechanical insight
This paper provides a new contribution regarding the use of DEM to simulate the micromechanical behavior of a graded asphalt mixture based on the research mentioned above
Summary
The traditional approach to model asphaltic materials is to treat them at the macro-scale using continuum-based models which are implemented into a finite element program. They have shown that the discrete element model is a useful tool to study the fundamental properties of asphalt concrete They further used ASBAL to simulate triaxial tests on Hot Mix Asphalt under different loading combinations where the Burger’s model was added in the normal and tangential directions at the contact between the particles [7]. The effect of the bitumen was represented by time-dependent shear and normal contact stiffnesses They used the model to predict the dilation in uniaxial compression tests for an axial stress of 400 kPa and triaxial tests for deviator stresses of 400 and 600 kPa at stress ratios of 0.6 and 0.8 [16]. Wu et al [20] used DEM to simulate constant strain rate compressive tests for an idealized asphalt mixture. A typical three-dimensional microstructural based discrete element viscoelastic modelling process is extremely
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