Examinando por Materia "Bitumen"

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    Estudio de mezclas binarias Asfalto-Polímero
    (IMPRENTA UNIV ANTIOQUIA, 2014-01-01) Múnera, J.C.; Alexander Ossa, E.; Múnera, J.C.; Alexander Ossa, E.; Universidad EAFIT. Departamento de Ingeniería de Producción; Materiales de Ingeniería
    Bitumen is a black material composed of a mixture of various natural hydrocarbons. Bitumen has been commonly used in road paving and roofing applications thanks to its hydrophobic and adhesives properties. The production of Polymer Modified Bitumens (PMB) has allowed the development of materials with better performance in comparison to pure bitumen. This work presents the effect of addition of polymer to a Colombian bitumen from its morphological, rheological and thermal properties, in order to identify different modification levels. The polymers used as modifiers were polyethylene wax (CPE), styrene butadiene styrene (SBS) and crumb rubber (CR). They were added to bitumen in proportions between 3 to 15% w/w. Both neat bitumen and PMB were characterized by penetration and softening point. Thermal and rheological characteristics were analyzed by differential scanning calorimetry (DSC) and rotational rheometry, respectively. Changes in the morphology were measured by atomic force microscopy (AFM). The experimental results showed that the CPE mixtures had the most pronounced effect on the conventional properties, achieving a 75% reduction in penetration and a 250% increase in the softening point compared to neat bitumen. The results obtained by DSC allowed identifying three glass transition temperatures (Tg) in neat bitumen. Mixtures with SBS altered Tg, showing changes on the thermal characteristics of neat bitumen. Mixtures with CPE and SBS showed the highest values of G*. The results obtained by AFM help identifying three different phases in neat bitumen and its variation with the addition of different polymer modifiers, showing considerable structural changes that led to changes in the material properties at the macroscopic level.
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    Thermo-oxidative aging of bitumen
    (Taylor and Francis Ltd., 2018-07-03) Gamarra, A.; Ossa, E.A.; Gamarra, A.; Ossa, E.A.; Universidad EAFIT. Departamento de Ingeniería de Producción; Materiales de Ingeniería
    Thermo-oxidative bitumen ageing has been commonly recognised as the main cause of asphalt cracking. The effect of thermo-oxidative ageing level on bitumen has been studied in this work by means of a simple and effective mechanical stirring process. Physical characteristics of the material as Softening Point, Penetration and Viscosity were measured to samples with different ageing conditions. Chemical changes in the material were evaluated by means of SARA fractioning to measure the effect of ageing on the fundamental components of bitumen, and Infrared Spectroscopy in order to study the changes found on the oxidation-related compounds of the material. Microstructural changes on the material were evaluated using atomic force microscopy (AFM) finding that the ageing process on bitumen increases the number and size of the phases related to asphaltenes and resins, and decreases the amount of phases related to aromatics. The changes in chemical and physical characteristics of bitumen were found to be strongly dependent on the carbonyl formation. An extension to a previously proposed oxidation kinetics model was used to predict the fast rate (transient) and constant rate (steady-state) oxidation behaviour of bitumen and its relation to physical properties. The thermo-oxidative changes suffered by bitumen are associated with increasing hardening of the material, making it susceptible to cracking when in contact with aggregate as thin films in flexible pavements. © 2016 Informa UK Limited, trading as Taylor & Francis Group.