A rheological comparison of hard grade binders with polymer modified bitumen under aged and unaged conditions

High ambient temperature and uncontrolled heavy axle loads are considered to be the root cause of premature failure of flexible pavements, especially rutting, in Pakistan. In order to combat rutting problems, 60/70 penetration grade bitumen modified with Elvaloy Terpolymer (PMB) has been used on various critical sections since 2001. Rheological characteristics of PMB, 60/70 and 40/50 penetration grade bitumen were studied using a dynamic shear rheometer at 25, 40 and 55 degrees C. Short term aging effects were also studied in a rolling thin film oven test and the results of aged and unaged binders have been compared. The study revealed that the complex shear modulus of binders reduces significantly with an increase in temperature, while the phase angle increases, but at a lesser rate. Short term aging has showed relatively less influence on binder rheology than temperature.