Polymer Testing 29 (2010) 588e595
Contents lists available at ScienceDirect
Polymer Testing journal homepage: www.elsevier.com/locate/polytest
Material Properties
Novel recycled polyethylene/ground tire rubber/bitumen blends for use in roofing applications: Thermo-mechanical properties Francisco Javier Navarro*, Pedro Partal, Francisco J. Martínez-Boza, Críspulo Gallegos Departamento de Ingeniería Química, Facultad de Ciencias Experimentales, Universidad de Huelva, Campus del Carmen, 21071 Huelva, Spain
a r t i c l e i n f o
a b s t r a c t
Article history: Received 3 February 2010 Accepted 16 March 2010
This paper summarises the effect of recycled polymers, such as ground tire rubber (GTR) and recycled polyethylene (RPE), on the thermal and rheological properties of modified bitumen blends. From the experimental results obtained, it can be deduced that GTR or RPE may enhance bitumen thermo-rheological behaviour. However, much more enhanced mechanical properties can be obtained using a combination of both recycled polymers. In that sense, GTR would mainly improve material behaviour at low in-service temperatures, since the glassy region is significantly shifted to much lower temperatures. Complementarily, RPE would mainly improve the high in-service temperature properties by largely increasing material elastic and viscous properties in this temperature region. As a result, and from an environmental point of view, the use of both GTR and RPE may contribute to solve a waste disposal problem, and to improve the quality of the resulting blends for roofing and waterproofing applications. Ó 2010 Elsevier Ltd. All rights reserved.
Keywords: Recycled PE Crumb tire rubber Modified bitumen
1. Introduction Nowadays, consumer’s new patterns have led to an extensive use of plastics and rubbers which, after their life cycle, represent an important problem for the environment, and creating a considerable waste disposal trouble. It is estimated that worldwide plastics production has grown up to 260 million tonnes in 2007 and, consequently, the amount of this material to be recycled has largely increased [1]. In addition, the amount of waste tires discarded worldwide each year is close to 330 million (approximately 4.4 million tons) and, taking into account that the average percent of natural and synthetic rubbers in tires is about 60%, it means that 2.64 million tons of waste tire rubber are generated per year [2,3]. The reutilization of postconsumer or postindustrial polymeric materials, and their return to industry, could be a suitable way of solving environmental concerns, offering low-cost recycled resources. * Corresponding author. Tel.: þ34 959218205; fax: þ34 959219983. E-mail address:
[email protected] (F.J. Navarro). 0142-9418/$ e see front matter Ó 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.polymertesting.2010.03.010
One industrial application of these materials is as a modifying agent for bitumen, since the resulting mixture may show similar performance to those containing virgin polymers [4]. Bitumen can be defined as a dark brown to black cementitious material, whose compounds can be classified into two generic groups, maltenes and asphaltenes. Asphaltenes is the black-coloured fraction, insoluble in n-heptane, and having the highest polarity and molecular weight, whereas maltenes, soluble in this solvent, are composed of saturated compounds, aromatic compounds and resins [5]. In general, virgin polymers are very useful for road pavements, and waterproofing and roofing membranes in order to improve the main distresses associated with bitumen: brittleness at low temperature that causes thermal cracking; low elastic and viscous properties at high in-service temperature that favour permanent deformation [6e8]. Consequently, replacing virgin by recycled polymers in bituminous blends is a promising alternative environmentally favourable, offering a sustainable life-cycle for some petroleum-derivative polymers. In this sense, two major groups of recycled polymers may be considered: crumb tire rubber and waste thermoplastic polymers.
F.J. Navarro et al. / Polymer Testing 29 (2010) 588e595
Using crumb tire rubber in bitumen modification contributes to achieve some environmental EU objectives, since, according to the directive (2000/53/EC), at least 85% of end of life vehicles weight must be re-used or recycled by 2015, and the landfill of scrap tires and other waste plastics is prohibited since 2006 [9e11]. It is well-known that an extensive study on the use of ground tire rubber as bitumen modifier has been already performed, pointing out improved mechanical properties, as increased fatigue life or fatigue resistance, reduced reflective cracking and low temperature cracking, tenacity, and larger resistance to rutting [6,12,13]. On the other hand, different recycled polymers have also been successfully used for modification of bitumen for paving purposes. The results obtained pointed out that they can improve the mechanical properties of the resulting binder. Examples of the use of these modifiers are polyethylene [14], polypropylene [15] and EVA [5]. Consequently, although the literature regarding the use of single recycled polymers as bitumen modifiers is very extensive, very few studies deal with the combined use of two different modifiers [16]. In addition, depending on the end-use of the modified bitumen, polymer concentration may vary to a large extent. Thus, for road paving applications, economical reasons and workability requirements (easiness of producing, handling, pumping, placing, and compacting) limit the amount of polymer in the mixture to low concentrations (usually