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Complex modulus characterization of cold-recycled mixtures with foamed bitumen and different content of reclaimed asphalt (RA)Cold-in place recycling with foamed bitumen is currently employed for the rehabilitation of road pavements, from local roads to heavy-duty motorways. The mechanical properties of foamed bitumen mixtures may vary from that of an improved granular material to that of an asphalt concrete, depending on their composition. The objective of the present study was to characterize the linear viscoelastic response of foamed bitumen mixtures with different content of reclaimed asphalt (50, 70 and 0 %). This objective was tackled by measuring the complex Young's modulus by means of uniaxial cyclic compression tests, in a range of temperatures (from -20 to 55 °C) and frequencies (from 0.03 to 10 Hz).The thermo-rheological behaviour was modelled using the Huet-Sayegh model, commonly used for bituminous mixtures. In order to focus on the influence of reclaimed asphalt content, the same grading and foamed bitumen content were used for all the mixtures. In addition, an effort was made to produce mixtures with similar volumetric properties. Considering all the tested mixtures, the stiffness modulus ranged between 171 to 4075 MPa, whereas the phase angle ranged between 4° to 18°. Though these values are well below those normally measured on asphalt mixtures, the frequency and temperature variations clearly highlight a typical asphalt-like behaviour. In addition, the time-temperature superposition principle can be considered valid, regardless of the reclaimed asphalt content. Overall the experimental results showed that it is possible to characterize the linear viscoelastic response of cold recycled foamed bitumen mixtures using the same experimental and analytical approach adopted for asphalt mixtures.

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