Bitumen modification with reactive and non-reactive (virgin and recycled) polymers: A comparative analysis F.J. Navarro a, *, P. Partal a , M. Garcı ´a-Morales a , M.J. Martı ´n-Alfonso a , F. Martı ´nez-Boza a , C. Gallegos a , J.C.M. Bordado b , A.C. Diogo c a Departamento de Ingenierı´a Quı´mica, Universidad de Huelva, Facultad de Ciencias Experimentales, Campus del Carmen, 21071 Huelva, Spain b Chemical Engineering Department, Instituto Superior Te ´cnico, Av. Rovisco Pais, 1049-001 Lisbon, Portugal c Materials Engineering Department, Instituto Superior Te ´cnico, Av. Rovisco Pais, 1049-001 Lisbon, Portugal 1. Introduction Bitumen is a complex mixture of different organic molecules. Despite its heterogeneity, bitumen compounds can be separated by chromatographic techniques into four generic groups (SARAs): saturates, aromatics, resins (which make up the maltene fraction) and asphaltenes. The complexity, aromaticity, heteroatom content, and molecular weight increase in the order S < A < R < As [1,2]. Concerning the microstructure, and according to the colloidal model, asphaltenes are dispersed into an oily matrix of maltenes and surrounded by a shell of resins whose thickness depends on temperature [3]. Thus, bitumen composition and temperature strongly influence the mechanical properties and microstructure of bitumen. Regarding its end-use, bitumen behaves as a viscoelastic material at usual in-service temperatures, showing mechanical/ rheological properties suitable for traditional paving and roofing applications [4,5]. However, the current traffic loads and volume of vehicles considerably reduce the lifetime of pavements. The most common distresses, directly associated to binder phase in road, are rutting (permanent deformation of the pavement in the form of ruts or corrugations) [6], and thermal cracking (fracture of the pavement due to the lack of flexibility at low temperatures) [7]. Traditionally, the performance of bitumen has been improved through the utilisation of additives such as virgin polymers (SBS, SBR, EVA, etc.), and waste polymers (plastic from agriculture, crumb tire rubber, etc.). However, the mixing process may have a significant effect on the technical properties of the resulting blend, as well as on the costs of the whole operation [8,9]. Thus, due to the high mixing temperatures involved (180 8C), the resulting binder may undergo ‘‘primary’’ ageing during processing, mainly due to the oxidation of maltene compounds, and polymer degradation [8,10,11]. In addition, polymer-modified bitumen is usually Journal of Industrial and Engineering Chemistry 15 (2009) 458–464 ARTICLE INFO Article history: Received 20 February 2008 Accepted 4 January 2009 Keywords: Modified bitumen Recycled polymer Reactive polymer Rheology Storage stability ABSTRACT The main goal of this research was to compare the modification capability of two different types of bitumen modifiers: non-reactive plastomers and elastomers, and reactive polymers. The group of non- reactive polymers included a block copolymer (SBS), recycled thermoplastic polymers (EVA/LDPE blends), and crumb tire rubber, which were mixed at a processing temperature of 180 8C. In the second group, a reactive MDI–PEG prepolymer, a low processing temperature modifier (90 8C), was considered. The study was mainly focused on the characterization of the thermorheological behaviour of selected modified bitumen samples. In addition, the thermal behaviour (by modulated DSC), and morphology (by optical microscopy) of these modified bitumen samples were also evaluated. All of these bitumen modifiers significantly improve the thermomechanical properties of the resulting binder, especially at high in-service temperatures. However, whereas bitumen modified by non-reactive polymers undergo marked oxidation events due to the high processing temperature used (180 8C), MDI–PEG modified bitumen does not experience this phenomenon because of the lower processing temperature involved (90 8C). In general, non-reactive polymers should be added in much larger concentrations than the reactive polymer to obtain similar results, although the latter requires a further period of curing, at room temperature, to induce suitable modification. Finally, only MDI–PEG modified bitumen is stable when stored at high temperature (163 8C), whereas all the non-reactive polymer-modified bitumen studied undergo either phase separation or particle precipitation. ß 2009 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved. * Corresponding author. Tel.: +34 959 218 205; fax: +34 959 219 983. E-mail address: frando@uhu.es (F.J. Navarro). Contents lists available at ScienceDirect Journal of Industrial and Engineering Chemistry journal homepage: www.elsevier.com/locate/jiec 1226-086X/$ – see front matter ß 2009 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved. doi:10.1016/j.jiec.2009.01.003