Implementing viscoelastic rheological methods to evaluate low temperature performance of modified asphalt binders Sassan Aflaki ⇑ , Pouria Hajikarimi 1 School of Civil Engineering, College of Engineering, University of Tehran, 16 Azarst., Enghelab Ave., Tehran, Iran highlights " Using a viscoelastic model to characterize low temperature performance of asphalt binders. " Determining Burgers model parameters by the principal of multiple non-linear regression. " Using derivation of creep compliance to grade low temperature performance of asphalt binders. " Comparing performance of the modified asphalt binders by three approaches. article info Article history: Received 22 January 2012 Received in revised form 7 April 2012 Accepted 25 April 2012 Available online 17 June 2012 Keywords: Viscoelastic Modified asphalt binders Low service temperature Bending beam rheometer Creep compliance abstract In this research, the effects of four modifiers including crumb rubber, gilsonite, styrene–butadiene–sty- rene (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 per- formed on different extent of modifiers at five temperatures: 6 °C, 12 °C, 18 °C, 24 °C and 30 °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 compli- ance. 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. Ó 2012 Elsevier Ltd. All rights reserved. 1. Introduction For the past two decades, using modifiers is so widespread in asphalt paving applications. Numerous researches have been de- voted to modified asphalt mixtures. These researches demonstrate that modifiers can increase the mixture resistance to thermal cracking, fatigue cracking and permanent deformation. Conse- quently, modifiers improve the performance of asphalt pavements at low, intermediate and high temperatures [1]. There are many modifiers which are used for modification of asphalt binders such as styrene–butadiene–styrene (SBS), styrene–butadiene–rubber (SBR), ethylene–vinyl–acetate (EVA), crumb rubber, gilsonite and polyphosphoric acid (PPA) [2]. There are several ways to classify modified asphalt binders. For this purpose, mechanism of altering asphalt properties by the modifier, the composition and mechanical characteristics of the modified asphalt binder; or the target asphalt property that needs improvement or increase can be studied [3]. Modifiers are investi- gated in this paper in accordance with the second way and effects of modifiers on the target asphalt mixture properties are not considered. There are several test methods for grading asphalt binders regarding to mechanical properties. Bending beam rheometer (BBR) is a well-known test which is widely implemented for 0950-0618/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.conbuildmat.2012.04.076 ⇑ Corresponding author. Tel.: +98 21 61112273; fax: +98 21 66403808. E-mail addresses: aflaki@ut.ac.ir (S. Aflaki), phajikarimi@ut.ac.ir (P. Hajikarimi). 1 Tel.: +98 936 3059039. Construction and Building Materials 36 (2012) 110–118 Contents lists available at SciVerse ScienceDirect Construction and Building Materials journal homepage: www.elsevier.com/locate/conbuildmat