Comparison of Rut Susceptibility Parameters in Modified Bitumen With Ppa

Pavement as a multi-layer structure is subjected to various distress mechanisms such as permanent deformation (rutting) in its service time. rutting resistance evaluation is one of the important components of pavement management system which plays a substantial role in the effective strategic development of pavement rehabilitation and maintenance. improving the rheological properties of bitumen using one of the various additives is one of the practical approaches to reduce the rutting potential in the asphalt mixture. in this study, basic bitumen with an 85/100 penetration grade (pg58-22) was modified by 0.5, 1.0 and 1.5% poly phosphoric acid by weight of bitumen. the rutting resistance improvement of modified bitumen was investigated according to superpave protocol. for this purpose, temperature sweep and frequency sweep tests were performed on all bitumen at 46, 52 and 58 oc. also, rutting resistance improvement ratio was calculated based on the superpave specification (|g*|/sinδ), shenoy specification (|g*|/[1-(1/sinδ×tanδ)]) and zero shear viscosity. this ratio was employed to rank these specifications. the results of this study represent an improvement in rutting resistance of modified bitumen. according to specification ranking results, it can be concluded that zero shear viscosity has more potential and credibility to predict rutting damage occurrence as compared to superpave specification and shenoy specification.