Thermo-viscoplastic law for bituminous mixes

ABSTRACT Bituminous mixes have rheological properties which depend on strain amplitude level. Their strongly viscous behaviour is linear for small strain level (some 10−5), then nonlinear for higher strain level. A maximum stress is reached at failure, which can be fragile (cracking) or ductile (flow). Moreover, this behaviour strongly depends on temperature. The thermo-viscoplastic law, developed at “Ecole Nationale des TPE” for bituminous mixes, is presented. This law introduces the various experimental observations: a general linear viscoelastic behaviour in the small strain range, non-linearity and viscoplastic flow. The effect of the temperature is described as well for small strain levels, where time-temperature superposition principle is applied, as for larger strain levels. This law is able to model the thermomechanical coupling phenomena, in particular, the Thermal Stress Restrained Specimen Test (TSRST). TSRST simulations show the influence of non-linearity on the thermal stress evolution induced by monotonic or cyclic temperature variation. A good simulation of this phenomenon is important for design of road structures.