3D DEM model simulation of asphalt mastics with sunflower oil

A three-dimensional particle model, based on the asphalt mastic micro-structure representation following a discrete element model framework, was developed to investigate the influence of sunflower oil (rejuvenator) on the rheological properties of asphalt mastic. Dynamic shear rheometer tests in laboratory, for a frequency range of 0.1-20 Hz and temperatures in a range between 20 and 80 degrees C, were carried out in order to assess the viscoelastic behaviour of asphalt mastics containing different oil to-bitumen content by mass proportions (2.5-20%). Master curves were constructed for two reference temperatures (30 degrees C and 50 degrees C). Experimental results showed that the increase in sunflower oil content resulted in a progressive decrease in viscosity. However, the rheological behaviour of the mastic containing the highest oil amount could not be properly represented in master curves, indicating that the specimen had a different rheological behaviour when compared with the lower oil contents responses. Numerical simulations of rheometer tests were carried out with an asphalt mastic particle assembly that emulated the experimental procedure. The viscoelastic contacts within the asphalt mastic assembly were simulated with a generalized Kelvin contact model. A calibration procedure was derived based on the fitting of laboratory data. The simulations were shown to have a good agreement with laboratory values. The average errors for the dynamic shear modulus and phase angle were 3.4% and 4.0%, respectively, considering both temperatures of analysis. Finally, a considerable improvement was accomplished in comparison with the numerical response obtained with the often-used Burgers model.