Energy Dissipation of Bituminous Mixtures with Crumb Rubber Added by Dry Process: Laboratory Tests and Numerical Simulation

In this study, the influence of crumb rubber added by dry process on the dissipative properties of bituminous mixtures has been investigated. Six mixtures were tested: two reference mixtures without crumb rubber were produced, one containing a pure binder and the other one containing an SBS-modified binder. Four other mixtures containing 2 % and 4 % (in mass) of crumb rubber and the same two mentioned binders were also produced. First, complex modulus tests were carried out at different frequencies and temperatures and for an axial strain amplitude of 50 mu m/m. The 2S2P1D analogical linear viscoelastic model was used to model experimental data. From these results, the dissipated energy during one sinusoidal loading cycle was calculated, both for constant strain amplitude loading and for constant stress amplitude loading. Simulations at constant strain amplitude show lower energy dissipation for bituminous mixtures containing 2 % and 4 % CR and the SBS-modified bitumen with respect to the corresponding reference mixture without CR. However, the opposite is found at constant stress amplitude. Mixtures containing pure bitumen and CR show lower dissipated energy for any loading mode. Numerical simulations were carried out to determine energy dissipation at the scale of a pavement structure. The linear viscoelastic properties determined experimentally for the different materials were implemented in a finite element model to perform the calculations in the frequency domain. Results show that pavements made with bituminous mixtures containing CR added by dry process dissipate more energy with respect to the reference mixtures without CR.