Effects of furfural activated crumb rubber on the properties of rubberized asphalt Khaldoun M. Shatanawi a,⇑ , Szabolcs Biro b , Andras Geiger c , Serji N. Amirkhanian d a Dept. of Civil Engineering, Faculty of Engineering and Technology, University of Jordan, Amman, Jordan b Bitumen Engineering, Veszprem, Hungary c MOL-Hungarian Oil and Gas, PLC, 2443 Szazhalombatta, P.O. Box 1, Hungary d Phoenix Industries, 4775 E. Cheyenne Ave., Las Vegas, Nevada 89115, USA article info Article history: Received 3 September 2009 Received in revised form 8 August 2011 Accepted 16 August 2011 Available online 1 October 2011 Keywords: Furfural Bitumen Asphalt Asphalt rubber CRM binder Activated crumb rubber Rheology Stability abstract The use of furfural (C 5 H 4 O 2 ) as an activation agent has been suggested as a method to improve the rhe- ological properties of asphalt binders due to its compatibility with crumb rubber. This study uses five dif- ferent crude sources and both ambient and cryogenic produced crumb rubber modifiers (CRM). The rheological properties for furfural activated and conventional CRM binders were evaluated using the dynamic shear rheometer (DSR) and the gel permeation chromatography (GPC). The results indicated that furfural activation has variable effects on the properties of the CRM binder. However, the most pro- nounced effect is shown in the storage stability improvement which will have an effect on the storage of CRM binder. Also, the activation caused a reduction in the ratio of the small molecular size distribution which is considered an improvement in the binder properties. Ó 2011 Elsevier Ltd. All rights reserved. 1. Introduction The addition of crumb rubber modifier (CRM) to asphalt/bitu- men has been shown and proven by many research projects and field applications to be an effective method of increasing the per- formance grade (PG) of the asphalt, improves the high temperature properties, decreases susceptibility to permanent deformation as well as providing resistance against reflective cracking [1–5]. It also provides an environmental option for the disposal of the scrap tires [6]. The main two processes used for producing crumb rubber mix- tures are the wet process and the dry process, in which the wet process is a more widely used process [7]. One of the disadvantages of using such a method is the possibility of producing a non- homogenous blend. Phase separation in rubber particles had been identified as a problem in the storage of CRM binders [8,9]. Such a behavior reduces the reproducibility of CRM binder using the wet process and may affect its properties [10]. Literature indicates that in order to minimize the problem associated with CRM particles settling, an easy way would be using the CRM binder in the field within 4 h of preparation [11]. The variation in stability found between different modified bind- ers could be as a result of the variation in the CRM composition [12], as modifying agents have different compositions and have different solubility in binders [13,14]. In a way to resolve this problem, researchers have been working on modifying the chemical bonds between the functional groups of the modifying agents and asphalt compounds [15–18]. The objective of this research was to study the effects of the fur- fural activation process on crumb rubber modified binder proper- ties. The use of furfural (C 5 H 4 O 2 ) as an activation agent has been suggested as a method to improve the rheological properties of as- phalt binders (chemically modified binders [19,20]), and the com- patibility of crumb rubber and asphalt [9]. The current patent [9] suggesting furfural as an activation agent presents limited data. Therefore, the rheological modification effects of the crumb rubber was evaluated. In order to properly investigate the stability of the modified CRM binder, the flow properties were investigated. Gel permeation chromatography (GPC) is a well known technique for characterizing the molecular size distribution of asphalt binders [21]. Therefore, GPC testing was conducted to determine if furfural had any effect on increasing the large molecular size (LMS) med- ium molecular size (MMS) distributions. 2. Materials Five different binder sources were used for this study. One from a Venezuelan source (A1), the second was from a Canadian origin (A2); third was mainly com- posed from a Middle Eastern source (A3), fourth was from a west Texas source 0950-0618/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.conbuildmat.2011.08.041 ⇑ Corresponding author. Tel.: +962 6 535 5000x22755. E-mail address: kshatanawi@ju.edu.jo (K.M. Shatanawi). Construction and Building Materials 28 (2012) 96–103 Contents lists available at SciVerse ScienceDirect Construction and Building Materials journal homepage: www.elsevier.com/locate/conbuildmat