Experimental characterization of the 3D linear viscoelastic behavior of cold recycled bitumen emulsion mixtures

Cold mixtures with bitumen emulsion are produced at ambient temperature, leading to substantial reductions of energy consumption and atmospheric emissions. In cold recycling applications, cement is normally used to improve the mixture performance. Thus, the rheological behavior of cold recycled mixtures is different from that of conventional hot mixtures because it is due to the interaction of fresh bitumen, aged bitumen and cementitious bonds. In this study, we investigated the three-dimensional (3D) linear viscoelastic (LVE) behavior of a cement-bitumen treated material (CBTM) mixture fabricated using bitumen emulsion and cement. For comparison, we also investigated the 3D LVE behavior of hot-mix asphalt containing 25% of reclaimed asphalt and fabricated using polymer-modified binder. Sinusoidal axial tests on cylindrical specimens, were carried out at various temperatures (from 0 °C to 50 °C) and frequencies (from 0.1 to 12 Hz). The complex Young's modulus E∗ and the complex Poisson's ratio v∗ were determined through the measurement of axial and transverse strain. We show that when considering E∗, CBTM mixtures may be considered thermo-rheologically simple and the Huet-Sayegh model can be used to simulate the frequency–temperature dependence. On the other hand, when considering v∗ the behavior of CBTM mixtures is very different from that of hot mix asphalt. In particular, its absolute value is almost constant and very close to 0.15.