Resilient modulus prediction of RAP using the Contact Dynamics Method

Abstract

Abstract The Optimal Recycling of Reclaimed Asphalts in low-traffic Pavements (ORRAP) project concerns a cold recycling of 100% Reclaimed Asphalt Pavement (RAP) without binder addition, in base and subbase layers of low-traffic pavements. The mastic coating of aggregates induces a viscoelastic behaviour and changes the resilient modulus with frequency and temperature. This modulus is obtained with repeated load triaxial tests and is a key element for pavement design. In this context, this paper presents a numerical alternative to predict this influence with a discrete approach. Contact Dynamics (CD) simulations are used to reproduce the resilient modulus test on a set of rigid spherical particles with a viscoelastic contact, based on the Burgers’ model. The tests were carried out with cylindrical samples at several frequencies for two temperatures (20 °C and 40 °C). The proposed model is calibrated in a given range of temperatures and frequencies regarding the experimental data, and then used to predict resilient modulus values at unreachable frequencies in the laboratory, with one set of parameters for each temperature. Finally, using the Williams-Landel-Ferry (WLF) equation, a master curve of resilient modulus at 20 °C as a function of the frequency was established. The Time-Temperature Superposition Principle (TTSP) reveals that the values at high frequencies and 40 °C correspond to the data at low frequencies and 20 °C.