Time-Temperature-Age Superposition Validation for Linear Viscoelastic Properties of Bituminous Materials

Aging, as an integral part of organic materials like asphalt binder, imposes a significant effect on chemical, physical, and performance-related properties of asphalt mixtures. One of the methods that has been proposed for consideration of aging in constitutive models of asphalt binder and asphalt mixtures within a linear viscoelastic range is time-temperature-age superposition of material function master curves. However, use of this method has not yet been verified for different bituminous materials. Thus, in this study, the validity of time-temperature-age superposition for different bituminous materials was tested. Furthermore, a valid framework to apply time-temperature-age superposition to viscoelastic material functions of asphalt binders was proposed. Oscillation tests within linear viscoelastic limits of asphalt binder and asphalt mixtures were applied on laboratory-aged specimens. Phase angle and complex modulus master curves were determined and the applicability of time-temperature-age shifting was evaluated. The results suggest that temperature-independent horizontal shift factors can be considered for asphalt binders. Furthermore, dynamic modulus testing of the asphalt mixtures at different aging levels shows that because of a local maximum existing in the phase angle master curve of asphalt mixture, horizontal and vertical shift factors cannot yield a superposition of the phase angle master curves. It can be concluded that time-temperature-age shifting cannot be used to implement aging in the constitutive models of asphalt mixtures.