Research On The Viscoelastic Properties Of Asphalt Using DMA

Dynamic mechanical analysis (DMA) is the method to study the viscoelastic properties of asphalt under cyclic stress and strain. DMA was employed to estimate dynamic mechanical properties of asphalt within different stress, strain, time, temperature and frequency region, which can not be obtained from others method.The morphology of multiphase/ multicomponent polymers not only has a pronounced influence on its rheological behavior, but also determinates its application properties to a great extent. The rheological properties of these systems are related to the phase morphology and interaction of the components, and can reflect sensitively the change of morphology. In this thesis, the relationship of morphology and rheological behavior for asphalt, modified asphalt and asphalt and mineral mastic were studied. DMA was used to study the effects of SBS modified and mineral filler on dynamic mechanical properties of SBS modified asphalt and mineral asphalt mastic, related physical mechanical properties were investigated also.The paper focused on viscoelastic properties of asphalt using DMA, consisting of the following researches:The morphologies of asphalt and modified asphalt were studied using DMA, according to the temperature dependence of Han curve, frequency depencence of dynamic viscoelastic properties, such as storage modulus, loss modulus and phase angle. In the homogeneous regime of binary polymer blends, temperature dependence for Han curve is not existed. However, in the pretransitional regime, the thermorheological complexities existed, which are shown as the temperature dependence of Han curve, enhanced elasticity and prolonged relaxation time, and storage modulus are more sensitive than loss modulus to phase separation. It is proved that modified asphalt is multiphase polymer within measured temperature and frequency.The application of time temperature superposition principle for asphalt and modified asphalt was studied using DMA according to the morphologies structure of asphalt and modified asphalt. In the homogeneous regime of binary polymer blends, time temperature superposition principle holds for dynamic viscoelastic properties. But in the pretransitional regime, time temperature superposition principle for dynamic viscoelastic properties is invalid. The shift factors of asphalt and modified aspalt were analyzed using WLF equation, including shift factors of static and dynamic viscoelastic properties and shift factors at low temperature.Asphalt and filler mastic is ont of the most important component of asphalt mixture, so it is especially necessary to research asphalt mastic composition, structure and performance. But the great performance difference between asphalt mastic, two-phase compound, and base asphalt leads to complexity of morphology of asphalt and filler mastic. DMA was used to study the morphology of asphalt and filler mastic. The interfacial interaction of asphalt and filler was analyzed from the loss gene tanδof asphalt and asphalt mastic, which is described as A.To analyze the dynamic viscoelastic properties of asphalt, dynamic viscoelastic constitutive equation was studied, consisting of generalized Maxwell model and fractional calculus Maxwell model. It is well known that the relaxation time spectra of asphalt are critical for viscoelastic functions, all viscoelastic functions belong to the same relaxation time spectra. The discrete relaxation time spectra of asphalt are calculated using non-linear regression method based on the dynamic frequency master curve. The result showed retardation time spectra can fit accurately the viscoelastic performance of asphalt and convert static dynamic viscoelastic functions. So we can obtain viscoelastic performance over a much larger time or frequency region than measurement results. It is concluded that the fractional calculus model can fit accurately the viscoelastic performance of asphalt and the fitting result can be used to evaluate the viscoelasitc performance of asphalt.