Implementing viscoelastic rheological methods to evaluate low temperature performance of modified asphalt binders

In this research, the effects of four modifiers including crumb rubber, gilsonite, styrene-butadiene-styrene (SBS) and polyphosphoric acid (PPA) on the mechanical and rheological properties of asphalt binder at low service temperature are investigated. The main objective of this paper is to rank modifiers due to their effect on low service performance characteristics of asphalt binder for all type and extent of observed modified asphalt binders. For this purpose, the bending beam rheometer (BBR) test is performed on different extent of modifiers at five temperatures: -6 degrees C, -12 degrees C, -18 degrees C, -24 degrees C and -30 degrees C. Asphalt binder is categorized as a viscoelastic material. Among several linear viscoelastic models, the Burgers model is selected for describing the mechanical behavior of modified asphalt binders. Four Burgers parameters are calculated by means of the principle of multiple non-linear regression and then these parameters are used for comparing the performance of asphalt binders by these three approaches: SuperPAVE Performance Grading (PG) protocol, dissipated energy ratio and derivation of creep compliance. Utilizing these three approaches, modified asphalt binders are ranked based on higher quantity of low temperature, dissipated energy ratio and derivation of creep compliance for all type and extent of modifiers alongside. Results show that each approach produces a particular grading which is not same as another one. In spite of variation of rankings, among the all evaluated modified asphalt binders, crumb rubber modified asphalt binder totally shows superior performance on low service temperature in all three methods. (C) 2012 Elsevier Ltd. All rights reserved.