Time Temperature Superposition Principle Validation for Bituminous Mixes in the Linear and Nonlinear Domains

The mechanical behavior of bituminous mixes is very complex. It is also characterized by great thermal sensitivity. In the small strain domain (for strain amplitudes below approximately 10−4), it can be considered to be linear, therefore the linear viscoelasticity theory can be applied. In addition, the time temperature superposition principle (TTSP) may be assumed, with a good approximation. This has been widely verified regarding the unidimensional behavior of bituminous mixes in the viscoelastic linear domain. This paper provides an overview of TTSP for bituminous materials, and three-dimensional (3D) behavior and nonlinear domain are also considered. The 3D behavior is characterized by measurements of the complex modulus and complex Poisson’s ratio. For both parameters, master curves are plotted to check the validity of TTSP in 3D. Some experiments in the nonlinear domain (considering strains up to some percentages and some crack propagation tests) are also conducted in equivalent conditions of time and temperature. The results show that the TTSP may be extended to the nonlinear domain, including the domain of crack propagation.