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Asphalt mixtures are time, temperature and stress dependent and categorized as viscoelastic materials. A wide range of models have been proposed to characterize the fatigue behavior of asphalt mixtures. In this study continuum damage theory is used to characterize fatigue properties of asphalt binders and their effects on mixture’s fatigue resistance. Neat, polymer modified and nanoclay modified bitumens were tested using linear amplitude sweep test. Four point bending beam fatigue tests were conducted on mixtures made with these binders at different loading rates namely 400, 600, 800 and 1000 micro-strain. Results showed that a strong correlation exists between the viscoelastic parameter of binder’s integrity and the fatigue resistance of asphalt mixtures. Furthermore, a phenomenological fatigue relationship was introduced which is a function of the strain loading of the mixture as well as the viscoelastic continuum damage properties of the binder phase in the mixture. The proposed model can be used as a surrogate to time consuming beam fatigue tests. [ABSTRACT FROM AUTHOR]

In stone mastic asphalt (SMA) mixtures the binder phase has an important role in the integrity of the mixture and should withstand the applied shear forces. Due to platy structure of nanoclay particles and having a large length over width ratio, they have considerable effects in enhancing properties of bitumens. In this paper the effects of nanoclay on high temperature properties of two distinct categories of SMA mixtures namely those with fibers and polymers have been investigated. A 60/70 pen grade neat bitumen, limestone aggregates, cellulose fibers and Styrene Butadiene Styrene (SBS) polymer alongside different dosages of montmorillonite nanoclay particles in the range of 1–4 percent by the weight of bitumen were used. Performance characteristics of different asphalt materials were evaluated in terms of the storage stability of modified asphalt binders as well as Marshall stability and flow, creep properties and rutting resistance of SMA mixtures having different amounts of nanoclay particles. Results revealed that the nanoclay polymer asphalt binders have higher storage stability as well as better performance characteristics. SMA mixtures with polymer modified asphalt binder have better permanent deformation characteristics (higher rutting resistance). Moreover, the SMA mixture containing 3% of nanoclay has the highest rutting resistance. [ABSTRACT FROM AUTHOR]

In this paper dissipated energy (DE) versus loading cycles is plotted, at the same time fatigue life of asphalt binders were investigated using of dissipated energy (DE) approach and based on linear and nonlinear strain levels. It was found that based on results obtained of time sweep test; there is a fair correlation between dissipated energy at the 50th loading cycle and fatigue life of asphalt binders in all strain levels. As a result, initial dissipated energy (IDE) is a parameter obtained from time sweep test, so the amount of initial dissipated energy (IDE) at the 50th loading cycle can be predicted the fatigue of asphalt binders without performing millions of loading cycles. [ABSTRACT FROM AUTHOR]