Bitumen modifiers for reduced temperature asphalts: a comparative analysis between three polymeric and non-polymeric additives

This study presents three bitumen modifiers which may find successful application in the fabrication of binders for warm mix asphalt in the paving industry. In that sense, two non-polymeric additives, thiourea and thiourea dioxide, along with a reactive isocyanate-terminated prepolymer have been evaluated. Viscous flow and linear viscoelasticity tests, at 60 ºC, reveal bituminous modified binders which evolve towards highly viscous materials when subjected to ambient curing. However, at 135 ºC, they show lower viscosity than a typical 3 wt.% SBS binder used as reference. These results suggest modified binders with low viscosity which may contribute to reduce the mix asphalt temperature. On the contrary, they are expected to undergo an important increase in viscosity when the asphalt is in service, which would contribute to improve further their performance. Low temperature performance and effects of short-term and long-term aging were not considered in this study.This work is part of a research project sponsored by a MEC-FEDER Programme of references BES-2008-003572 and AP2008-01419, supported by European Social Fund. The authors gratefully acknowledge its financial support

Influence of the prepolymer molecular weight and free isocyanate content on the rheology of polyurethane modified bitumens

Isocyanate-based modification is lately gaining acceptance as a successful way to give added value to bitumen, a crude oil refining by-product. In order to study the influence of prepolymer type on the rheological properties of the resulting binders, six prepolymers synthesized from polypropylene-glycols (PPG) with varying molecular weight (between 440 and 2425) and different molar excess of a polymeric MDI (4,4’-diphenylmethane diisocyanate) were used. Two modification procedures, either involving or not water addition were followed. The modification achieved depends on both the selected polyol molecular weight and the excess in MDI (i.e., free isocyanate content), although not in a similar extent. Viscous flow and dynamic oscillatory shear tests, at 60 ºC, demonstrated a much higher level of bitumen modification by using the prepolymer prepared with the polyol having a molecular weight of 940 and with a free isocyanate content of 17.4 wt.%, mainly after addition of water. On the other hand, bitumen nature greatly affects the final rheological properties of these bituminous products. In that sense, modification results much more effective when conducted on bitumen with a well-developed colloidal microstructure.This work is part of two research projects sponsored by a MEC-FEDER Programme (Research Project MAT2007-61460) and by a Junta de Andalucia Programme (TEP6689). The authors gratefully acknowledge their financial support. A.A. Cuadri also thanks “Ministerio de Educación” for the concession of a F.P.U. research grant (AP2008-01419)

CIBERER : Spanish national network for research on rare diseases: A highly productive collaborative initiative

Altres ajuts: Instituto de Salud Carlos III (ISCIII); Ministerio de Ciencia e Innovación.CIBER (Center for Biomedical Network Research; Centro de Investigación Biomédica En Red) is a public national consortium created in 2006 under the umbrella of the Spanish National Institute of Health Carlos III (ISCIII). This innovative research structure comprises 11 different specific areas dedicated to the main public health priorities in the National Health System. CIBERER, the thematic area of CIBER focused on rare diseases (RDs) currently consists of 75 research groups belonging to universities, research centers, and hospitals of the entire country. CIBERER's mission is to be a center prioritizing and favoring collaboration and cooperation between biomedical and clinical research groups, with special emphasis on the aspects of genetic, molecular, biochemical, and cellular research of RDs. This research is the basis for providing new tools for the diagnosis and therapy of low-prevalence diseases, in line with the International Rare Diseases Research Consortium (IRDiRC) objectives, thus favoring translational research between the scientific environment of the laboratory and the clinical setting of health centers. In this article, we intend to review CIBERER's 15-year journey and summarize the main results obtained in terms of internationalization, scientific production, contributions toward the discovery of new therapies and novel genes associated to diseases, cooperation with patients' associations and many other topics related to RD research

The development of polyurethane modified bitumen emulsions for cold mix applications

Bitumen emulsions stand for an alternative paving practice to the traditional hot-mix asphalts. In addition, modified bitumen emulsions show a better performance than unmodified ones. This work studies the feasibility of obtaining polyurethane modified bitumen emulsions, in which an isocyanate-functionalized polyol constitutes the bitumen modifier (in varying concentration from 1 to 4 wt.%). Storage stability and high in-service performance are evaluated by means of evolution of droplet size distribution (DSD) and rheology tests, respectively. Regarding the emulsion stability, the key factor seems to be the bitumen modifier concentration used to prepare the modified emulsions. Thus, for a selected 50 wt.% bitumen fraction, there is a limit concentration (between 1 and 2 wt.%) above which the emulsion becomes unstable under storage. Hence, this result limits the modifier content that can be used in the emulsion and the final level of modification achieved if compared to the original non-modified emulsion. On the other hand, the rheological characterization conducted on the emulsion residues at 60ºC has shown an improved resistance to deformation. In terms of applicability, polyurethane modified bitumens allows for the obtaining of modified emulsions which can be prepared at much lower temperatures than those derived from other polymers.This work is part of two research projects sponsored by a MEC-FEDER Programme (Research Project MAT2007-61460) and by a Junta de Andalucia Programme (TEP6689). The authors gratefully acknowledge their financial support. A.A. Cuadri also thanks “Ministerio de Educación” for the concession of a F.P.U. research grant (AP2008-01419).This work is part of two research projects sponsored by a MEC-FEDER Programme (Research Project MAT2007-61460) and by a Junta de Andalucia Programme (TEP6689). The authors gratefully acknowledge their financial support. A.A. Cuadri also thanks "Ministerio de Educacion" for the concession of a F.P.U. research grant (AP2008-01419)

Hybrid Rubberised Bitumen from Reactive and Non-Reactive Ethylene Copolymers

Hybrid modification is a relatively new concept of incorporating two or more polymeric modifiers of different nature to a bitumen, in order to take advantage of their complementary features. Aiming to this, in this paper, the so-called Hybrid Systems (HSs) were prepared by the addition of an ethylene-based copolymer (reactive or non-reactive) to a model rubberised binder (Crumb Tyre Rubber Modified Bitumen). The resulting binders (referred to as reactive and non-reactivate HSs, depending on copolymer used) were evaluated by means of thermorheological analysis, technological characterisation, fluorescence microscopy and modulated differential scanning calorimetry. From the experimental results, it may be deduced a positive synergistic effect of non-dissolved Crumb Tyre Rubber (CTR) particles and a second polymeric phase that not only improves the in-service performance but also the high-temperature storage stability. This enhancement is attributed to the development of a multiphasic system composed of non-dissolved CTR particles, a polymer-rich phase and an asphaltene-rich phase. In the case of non-reactive HSs, droplets of swollen ethylene copolymer form a well-defined dispersed phase. By contrast, reactive HSs display a different morphology, almost invisible by optical microscopy, related to the development of a chemical network that yields, by far, the highest degree of modification