| Asphalt's complex chemical structure varies with its origin and method of production and thus asphalt is not a simple material to study. Even though asphalt constitutes only a small fraction of the complex construction composite (hot-mix asphalt concrete) it has a significant impact on the performance of pavements.; When used for paving applications, asphalt from crude oil distillation does not provide efficient resistance towards factors influencing the quality of the pavement (temperature extremes, imposed stress, accumulated strain, etc.). That is why it is being frequently modified by various additives, mostly polymers.; The bond of the polymer with asphalt was proved not to be of chemical, but rather of physical nature with the help of FTIR spectra.; Dynamic data served as a tool for revealing of the main transitions in asphalt. On top of the two main transitions in this material, another transition at very low temperatures was found in SBS modified asphalt. Transition at high temperatures was found in EVA modified asphalts, this one representing crystallization in EVA polymer.; Study of the viscosity function showed the clear difference between unmodified and modified asphalts. In this measurement, non-linearity is introduced by the application of high shear rates and as a consequence, the inner structure can be clearly identified. Whereas unmodified asphalts behave mostly as Newtonian liquids, modified asphalts, especially at higher concentration, are strictly non-Newtonian. Four distinctive regions were found at various concentrations of the polymer and various temperatures, thus pointing to the temporary nature of the transient network. These regions are assigned to the rearrangements of the molecules and polydomains in asphalt and polymer.; Dynamic creep experiments gathered information on the permanent deformation after cyclic loading and unloading of the stress and thus simulating the situation in the field. By variation of the test variables, the time-evolving structure and some non-linear effects were observed. In some cases (SBS modified asphalts), the zero-shear viscosity (considered as a possible replacement of the currently used specification parameter) is different from the real value of zero-shear viscosity for the tested material. These effects point to some difficulties, which might arise, when the dynamic creep is considered as the experiment, on which the definition of a new specification parameter is to be used. |
