Bitume | EPFL Graph Search

Le bitume est un matériau présent naturellement dans l'environnement ou pouvant être fabriqué industriellement après distillation de certains pétroles bruts. Il est composé d'un mélange d'hydrocarbures, peut se trouver à l'état liquide ou solide, et a une couleur brunâtre à noirâtre. Le bitume est liquéfiable à chaud et adhère aux supports sur lesquels on l'applique. Il possède un certain nombre de qualités physico-chimiques dont l'être humain a su faire usage depuis la Préhistoire. Dans le langage courant, on le confond souvent avec la poix, le goudron d'origine houillère, ou l'asphalte routier dont il n'est qu'un composant. Les premiers témoignages de son utilisation remontent à la Préhistoire où il était employé en tant qu'adhésif dans l'industrie lithique (Umm el-Tlel, site localisé en Syrie centrale et daté du Paléolithique moyen). À partir du Néolithique, ses utilisations se sont diversifiées, notamment au Proche et Moyen-Orient, et ses techniques se sont enrichies. Il fut util

Modélisation et prédiction du comportement rhéologique des mélanges bitume caoutchouc

Mehdi Ould Henia

Asphalt rubber is a modified binder widely used in pavement construction. Composition design methods of asphalt rubber blends are exclusively empiric and rely on the selection of the optimal combination of parameters after a long experimental program. The understanding of the phenomena affecting the asphalt rubber behaviour starts with the proposal of a rational theory and its validation with experimental data. To do so, a set of experiments were carried out including three main factors considered as significant for the rheological behaviour of the final binder. These factors are the bitumen chemical composition, the rubber content and its maximum mesh size. The binder complex shear moduli were measured within the viscoelastic linear domain. The measurements allowed a full characterisation of the rheological behaviour of asphalt rubber for the service temperatures and rates of loading. Base bitumen composition leads to final binders with rheological behaviours that are radically different despite the fact that the base bitumen belong to the same commercial grade. The rubber content increase showed significant changes on the properties of the binder, especially an increase of its elasticity and a decrease of its temperature sensitivity. The rubber powder maximum mesh size has no significant effect on the rheological properties of the blends within the service conditions. An analysis of physical and chemical changes was carried out on the phases formed after the curing process. A method for the isolation of the phases without affecting their physical and chemical properties was proposed. A centrifuging process was applied to asphalt rubber thanks to the design of an appropriate equipment adapted to the binder features. An experimental protocol was established to obtain a good separation of the phases with a limited aging. The SARA bitumen group analyses were carried out before and after the curing process. They allowed the determination the bitumen fractions kinetics during the blending. Light fractions of bitumen are the main chemical groups that migrate toward the cross-linked rubber network causing its swelling. The rheological behaviour of the separated bitumen phase has proven that the residual bitumen exhibits a lowered thermal sensitivity which is confirmed by the increase of the colloidal instability index. The rubbery phase has showed an extent of swelling varying between 200 and 400% which modifies considerably the rheological behaviour of the rubber by transferring to it a part of the thermal sensitivity of the bitumen. The influence of the factors was evaluated and their relative importance determined through a statistical model. Micromechanical modelling of the asphalt rubber composite has allowed the validation of observed phenomena that are mainly physical ones. To do this, two main homogenisation procedures were implemented and carried out on the heterogeneous medium: The classical self-consistent approach widely referenced as the equivalent medium approach (EMA) and the generalised self-consistent approach frequently referenced as the equivalent field approach (EFA). A satisfactory modelling of the composite is achieved by taking into account two changes occurring in the phases: their volumetric fractions influenced by the swelling, and their rheological properties due to the diffusion of bitumen into the rubber. An acceptable estimation of the rheological behaviour of the rubbery phase is obtained from the base materials properties with a three-phase self-consistent modelling according to EFA approach. The consideration of an adsorbed fraction of the bitumen on the surface of the rubber particle has allowed a qualitative and a quantitative description of the properties of the rubbery phase. The difficulty of predicting the rheological behaviour of a bitumen from its chemical composition is discussed. Future investigation ways are proposed.

EPFL2005

A framework for characterizing RAP clustering in asphalt concrete mixtures

Sara Bressi, André-Gilles Dumont, Manfred Partl, Michel Pittet

Recycled Asphalt Pavement (RAP) is commonly used in asphalt for road rehabilitation or new constructions. Nevertheless, some physical and chemical phenomena that occur during production, laying and compaction of mixtures containing RAP are not yet completely explored. One of the main aspects is represented by the interaction between the aged bitumen from RAP and the virgin bitumen added to the mixture as well as the creation of clusters among small-size RAP particles. In this paper several combinations of mixtures are studied, varying the amount of RAP, the type of new binder and the testing temperature in order to obtain a suitable data set for the development of a framework for characterizing clustering of RAP during mixing hot recycled asphalt concrete based on the parameters mentioned above. For analyzing the experiments, the Response Surface Methodology (RSM) was applied. The set of points (combinations tested) for calibration of the models was selected using the Dohelert network, which is a design optimization strategy that allows the effective estimation of the models coefficients. The agglomeration of RAP particles is investigated for all virgin binders used and for all the percentages of RAP. It was shown that the quantity and the quality of virgin aggregates play a significant role in the clusters formation. Moreover, this experimental work suggested that revised formula for the calculation of the bitumen film thickness is needed, in order to include the combined effect of bitumen penetration and fabrication temperature. (C) 2015 Elsevier Ltd. All rights reserved.

Elsevier Sci Ltd2016

High stiffness underlayers with high percentage of re- use as developed in the NR2C-project

Nicolas Bueche

New Road Construction Concepts (NR2C) is a FEHRL- project supported by the European Commission under the Sixth Framework Programme. NR2C aims at developing perspectives and specific innovations in different areas. One of the ideas concerns the development of high performance underlayers with high percentage of reclaimed asphalt. Three different mixes were designed, optimized and compared, namely with 0 %, 25 % and 40 % reclaimed asphalt. After an extensive laboratory study, the selected solutions have been further studied in a full- scale ALT facility. The structure tested has been instrumented with strain gauges, deflection and temperature sensors in order to analyse the performances. In a first step, fatigue behaviour was evaluated by applying 100'000 12-tons axle loads at 15 ° C. Then, low temperature behaviour was investigated by load applications during a number of temperature cycles where the air temperature varied between +2 °C and -7 ° C. In addition to the ALT, tests on large slabs with extreme temperature and other laboratory tests on mixes and binders have been performed. Finally, no negative effect using a high percentage of reclaimed asphalt has been found within this study. However key parameters as for instance the mix design and RA properties require special attention.

EMPA2008

Modélisation et prédiction du comportement rhéologique des mélanges bitume caoutchouc

Mehdi Ould Henia

EPFL2005