ABSTRACT
Dissipation is a powerful tool for characterizing fatigue behaviour and has been employed for various materials. But the use of dissipation in characterizing fatigue of bituminous concrete is complicated by the presence of other modes of dissipation than fatigue, particularly dissipation due to viscous friction. The challenge is therefore to separate fatigue dissipation due to repeated loading from viscous dissipation. Some methods have already been suggested the same including the use of the Dissipated Pseudo-Strain Energy (DPSE) and the Ratio of Dissipated Energy Change (RDEC).
In this study, the two primary methods available for separating fatigue dissipation, DPSE and RDEC, were analysed using principles of thermodynamics and experimental observations in the literature. It was found that while they are useful in certain specific cases, these methods cannot be universally used in all laboratory and field tests.
Accurate estimation of fatigue and viscous dissipation requires accurate characterization of the viscoelastic behaviour of damaged bituminous concrete. However, fatigue of bituminous concrete occurs at higher stress levels. It is difficult to conduct experiments to elicit the pure viscoelastic behaviour at such stress levels as experiments at high stress levels tend to damage the specimen. It is therefore necessary to make some constitutive assumptions about the viscoelastic behaviour of damaged bituminous concrete. One such constitutive assumption was used in this study to develop an alternative method to estimate fatigue dissipation. Fatigue dissipation was estimated using this method for bituminous concrete prepared with one unmodified binders and two binders modified by a plastomer and an elastomer.
