The impacts of two different groups of polymers on the mechanical and theological properties in a hard base asphalt were investigated. One group was modified with a reactive polymer, Elvaloy (R) 4170, with or without polyphosphoric acid (PPA). The other group used in this study was styrene butadiene styrene (SBS) D1101, either crosslinked with sulfur or not. The theological properties of these materials were investigated by small-amplitude oscillations and steady-state shear viscosity. It was shown that the properties of a polymer modified asphalt blends beside depending on the type of polymer are strongly dependent on the presence of PPA and sulfur as it was clearly manifested in dynamic experiments. Steady state shear viscosity measured at 60 degrees C showed a possible chemical interaction between Elvaloy and PPA. The blends with SBS D1101 (at the same temperature) showed a more complicated behavior. (C) 2015 Elsevier B.V. All rights reserved.