Complex Modulus of Cold Recycled Mixtures: measurement and modelling

In the present study, the complex modulus E* of three types of cold recycled mixtures was measured in the laboratory using cyclic compression tests. The mixtures, that were produced in situ using the full-depth reclamation technique, were characterised by the same 100% reclaimed aggregate composition, whereas bitumen emulsion, foamed bitumen and portland cement were employed as binding agents. Complex modulus testing was carried out on cylindrical specimens cored from the pavement seven years after construction. A sinusoidal strain with amplitude of 30 microstrain was applied at testing temperatures ranging from 0 to 50 °C and frequencies ranging from 0.1 to 20 Hz. Results showed that the time-temperature superposition principle was fully verified for the stiffness modulus whereas some discrepancy was highlighted by the loss angle. The Huet-Sayegh rheological model was applied to simulate the experimental data. Model fitting based only on the stiffness modulus provided excellent results. Indeed, the fitted rheological model was also able to simulate the loss angle variation quite well, but with some underestimation (about 3°) of the measured values. It can be concluded that other dissipation mechanism, in addition to the “classical” viscous type, were influent for behaviour of the studied cold recycled mixtures.