Characterization of Visco-Elastic Properties of Locally Available Asphalts in Pakistan

Asphalt is a visco-elastic material having properties of elastic solid at low temperature and viscous liquid at high temperature. Properties of asphalt binder depend upon temperature, rate of loading and aging conditions. Although asphalt binder is only 4-5 % of asphalt concrete mix by weight but it plays a vital role in defining the pavement performance. That is, pavement response is heavily dependent upon the viscous and elastic properties of asphalt. In this research six asphalt samples were obtained from Attock and Karachi oil refinery and Dynamic Shear Rheometer was used in the laboratory to evaluate their viscous and elastic properties. Witczak predictive model was used to predict the binder viscosity and phase angle by using complex shear modulus and viscosity temperature susceptibility. The study revealed that Karachi virgin asphalt grades are more elastic as compared to Attock virgin asphalt grades both at low and high temperature. Similarly Attock PMB is more stiff and elastic as compared to Karachi 40/50, 60/70, and Attock 60/70. The research also revealed that Attock PMB has lesser temperature susceptibility as compared to virgin grades which makes it more suitable to resist rutting and cracking in extreme climatic conditions of Pakistan.