Rheological characteristics of ground tire rubber-modiﬁed bitumens F.J. Navarro, P. Partal∗ , F. Mart´nez-Boza, C. Valencia, C. Gallegos ı Departamento de Ingenier´a Qu´mica, Universidad de Huelva, Escuela Politécnica Superior, Ctra. de Palos de la Frontera s/n, 21819 Huelva, Spain ı ı Accepted 4 February 2002
Abstract This work deals with the characterisation of the linear viscoelastic properties, closely related to its performance as road paving binder, of ambient ground tire rubber-modiﬁed bitumen. Speciﬁcally, the inﬂuence that rubber particle size exerts on the rheological properties of these binders has been studied. The resulting viscoelastic behaviour has been compared with that shown by unmodiﬁed and polymer-modiﬁed (SBS) bitumens. In total, an unmodiﬁed bitumen, ﬁve ground tire rubber-modiﬁed and three polymer-modiﬁed (SBS) bitumens have been studied. Rubber-modiﬁed bitumens show improved viscoelastic characteristics and, therefore, higher viscosity than unmodiﬁed binders. Consequently, enhanced resistance to permanent deformation or rutting and low-temperature cracking should be expected in ground tire rubber-modiﬁed bitumens. In addition, rubber-modiﬁed bitumen (9 wt.%) shows very similar linear viscoelastic properties to SBS-modiﬁed bitumen having 3 wt.% SBS at −10 ◦ C, and 7 wt.% SBS at 75 ◦ C. © 2002 Elsevier Science B.V. All rights reserved. Keywords: Bitumen; Viscoelastic behaviour; Crumb rubber
1. Introduction Bitumen has been widely used as an adhesive material in pavement mixtures, surface dressing, bridge deck waterprooﬁng, overlays and the protection of buildings, for example waterprooﬁng roof and joint and crack seals. This is because asphalt is strong, readily adhesive, highly waterproof and durable . In general, the components of bitumen can be broadly categorised as maltenes and asphaltenes. The viscoelastic properties of bitumen, and consequently its performance as a road paving binder, are dramatically inﬂuenced by the ratio between the asphaltene and maltene fractions [2–4]. There are several major distresses of road pavement related to bitumen properties. Since bitumen is a viscoelastic material, its rheological properties are very sensitive to temperature as well as to the rate of loading. With respect to temperature, the most frequent problems of road pavement are rutting, fatigue cracking and thermal cracking . Polymer modiﬁcation has beneﬁcial effects on bitumen binders and therefore on road pavements: decreased thermal susceptibility and permanent deformation (rutting) and increased resistance to low-temperature cracking, since the binder undergoes a decrease in its effective glass transition temperature [3–8]. ∗ Corresponding author. Tel.: +34-95901-7421; fax: +34-95901-7477. E-mail address: firstname.lastname@example.org (P. Partal).
A limited number of polymers have been used as modifying agents. However, the high cost of these polymers compared to bitumen means that the amount of polymer needed to improve pavement performance should be as small as possible . This major restriction could be avoided by using recycled polymers, such as granulated tire rubbers. From an environmental and economic standpoint, the use of ground tire rubber as a bitumen-modifying agent may contribute to solving a waste disposal problem and to improving the quality of road pavements. Two different ground tire rubbers may be obtained depending on the temperature of the process: (A) ambient ground rubber, which is obtained at room temperature and has a sponge-like surface that, consequently, has a large surface area, which increases the reaction rate with bitumen. (B) cryogenically ground rubber, which is obtained at or below the embrittlement temperature of the rubber, and produces clean ﬂat surfaces, which reduce the reaction rate . Different studies have noted the relationship between the rheological characteristics of asphalt binders and ﬁeld performance...