INVESTIGATION OF POLYMER MODIFIED ASPHALT BY SHEAR AND TENSILE COMPLIANCES

Although C-SHRP and Superpave procedures are currently being used in the testing of polymer modified asphalt (PMA) and asphalt binders, it is believed that further laboratory investigations will have to be done in the field of loading time and temperature from the perspective of rutting, fatigue and low temperature cracking. One possible method of investigation with the advantage of providing more insight into the material structure is to characterize materials on larger time / frequency domains by accepting the Time Temperature Superposition (TTS) principle. The goal of this paper is to summarize the findings from the tests of the PMA binders that were examined by the dynamic shear and bending beam rheometers (DSR and BBR). Two commercially available binders of different performance grades (PG’s) were investigated. Binder results were compared with the results of mastic - mix of asphalt binder and mineral filler, and hot mix asphalt (HMA). This was investigated using a dynamic mode (oscillations) and creep sample test. The TTS principle was applied to the obtained master curves from the isochrones of three of the tested materials (PMA, mastic and HMA). Preliminary results showed that the performance of shear compliance of the HMA is similar to binder and mastic at short loading (and/or low temperatures) but exhibited different behavior at long time loading (and/or high temperatures). The paper also discusses a question of the relation between the shear and tensile compliances (J,D(t)). These were obtained for original PMA, HMA and mastic by the relaxation of the spectra from master curves. Results of the tested binders showed a relationship among these fundamental parameters, which is important for proper asphalt binder evaluation. This is in accordance with AASHTO 2002 design, where materials tend to be described by still the empirical method but based on mechanical principles.