Rheology of rubber modified bitumen with mechanical behaviour prediction

SCOPE OF THE RESEARCH • Experimental determination of the composite rheology • Modelisation of the composite viscoelastic behaviour • Investigation on the interactions between components • Proposal of predictive models for the mechanical behaviou

Effect of base bitumen composition on asphalt rubber binder properties

The asphalt rubber blend properties are strongly related to its base components properties. The base bitumen composition is considered as a key factor influencing the final rheological properties of asphalt rubber binder. This paper describes results from a laboratory investigation of the interaction between crumb rubber and different composition bitumen according to the wet process. The bitumen composition is determined according to the SARA decomposition approach. The composition’s analyses are carried out on both base bitumen and residual bitumen extracted from the final asphalt rubber blend. The extraction process consists of a centrifuging procedure ensuring a reasonable aging and a minimum physical or chemical alteration of the phases. The evolution of the bitumen composition during the curing process indicates that aromatic fractions of bitumen are the major cause of rubber swelling through a migration phenomenon. Viscoelastic properties measurements demonstrate that base bitumen composition should be selected carefully to achieve a good compromise between a sufficient rubber swelling and a reasonable viscosity of the final binder

New Method for Pavement Rutting Prediction

In recent years, pavement rutting rate has increased significantly due to constant traffic intensity increment. These solicitations affect the bituminous layers that can quickly attain their permanent deformation limit resistance. This phenomenon can lead to a pavement depression, located in the tyre-road contact surface. The purpose of this paper is to present a methodology to estimate the rutting of bituminous pavements and to predict the rutting risk considering the bituminous mix rutting resistance characteristics obtained with the LPC traffic simulator, and taking into account the traffic and environmental characteristics. The traffic characteristics are represented by the total heavy traffic expressed in equivalent single axle loads (ESAL) passed on the pavement during the service period, and the heavy vehicles speed on the considered section. The environmental characteristic is represented by the pavement temperature at 2 cm depth. The developed model starts from the widely used empirical rutting formula and its experimentally determined coefficients. The general concept of the model is to start from this generalised rutting formula and to apply it to the real rutting behaviour occurring in pavements. For this purpose, observations and material analysis of eleven in place pavements were made. The model was calibrated using eleven bituminous mixes and verified introducing the characteristics of four in place bituminous mixes not considered in the initial calibration phase. The developed model gives rut depth values after having determined material and site characteristics and presents a good correlation coefficient with very satisfactory results in its verification phase with additional materials

Elaboration d'un plan des classes de trafic pondéral du réseau routier de la ville de Lausanne

La présente étude vise à fournir une analyse du trafic lourd présent sur le réseau routier de la ville de Lausanne et établir la classe de trafic pondéral de chacune des routes du réseau principal. Le rapport établi donne les explications nécessaires à la compréhension de la démarche et à l’utilisation du fichier Excel « Détails de la détermination des CT » qui constitue l’élément principal de l’étude. Ce fichier contient toutes les étapes depuis le recensement des différents bus par tronçon de route jusqu’à la détermination de la classe de trafic, il reprend l’ensemble des données et donne les résultats obtenus

High modulus pavement design using accelerated loading testing (ALT)

In anticipation of the introduction of high modulus materials in the Swiss standards, a research project has been carried out for the evaluation of these bituminous mixtures. Three full-size test sections were built in a test hall for ALT named Halle-fosse: Two sections with two different high modulus bituminous mixtures (named EME, abbreviation of the French designation of the mixture: Enrobé à Module Elevé) as base layer, whereas the third section, used as reference, had a standard bituminous material base layer. The three structures were designed to have an equivalent fatigue resistance and were submitted to loading with a traffic simulator. This device, a truck axle, permits to simulate heavy traffic on roads. Strains were measured for different types of loading at different temperatures, in order to assess the response of the structure. Equivalency factors for both types of EME mixtures were established using, as a basis, the French design method

Ecoulement des eaux de surface dans l'enrobé drainant sur le pont de l'Arnon - autoroutier

Vérification in situ de certains aspects qualitatifs de l'écoulement de l'eau de pluie dans la masse de l'enrobé drainant; évaluation de la perméabilité et du comportement hydrique en général

Liants au bitume caoutchouc. Une technologie innovante vieille de 40 ans !

Il n'est pas nécessaire de présenter la problématique déjà très médiatisée des pneus usagés qui s'entassent dans les décharges. Les directives européennes devant entrer en vigueur d'ici 2008 vont progressivement interdire la mise en décharge des pneus sous toutes les formes et rendre plus sévères les normes sur les émissions de gaz des cimenteries utilisant le caoutchouc comme combustible alternatif. L'utilisation du caoutchouc de pneu dans les matériaux routiers est une alternative séduisante au recyclage de ces "déchets". Elle ne peut toutefois pas prétendre à pouvoir résorber tout le stock de pneus usagés. Néanmoins chaque quantité "valorisée" par ce type d'utilisation est une contribution non négligeable à l'amélioration du bilan énergétique sur le cycle de vie total de ce matériau exceptionnel qu'est le caoutchouc. Le bitume caoutchouc est un mélange à haute température de bitume avec de la poudre de caoutchouc recyclé moyennant parfois quelques ajouts. Il est souvent présenté par les fabricants comme le produit miracle. Pour les agences, c'est plutôt le produit casse- tête. De part la nature complexe de ce liant modifié, on se heurte souvent au problème de proposer des exigences de qualité. Il est donc intéressant de tirer profit des expériences internationales pour maîtriser à moindre coût cette technologie. Comme pour les Bmp, l'ingénieur routier doit se familiariser avec ce produit et savoir quels sont les critères qui doivent être contrôlés et évalués pour comparer ce qui est comparable. Dans l'état actuel des choses, le bitume caoutchouc est un liant modifié avec des performances légèrement en deçà de celles des Bmp. Il constitue néanmoins une alternative prometteuse essentiellement dans des projets de réfection. Le produit doit dans les années à venir s'imposer par ses performances et non pas par ses arguments politiques ou environnementaux. Le potentiel est là, il ne reste plus qu'à l'exploiter

Unterhalt 2000 - FP7, Planches d'essais in situ sur l'autoroute A2/BL

Afin d'évaluer in situ le comportement mécanique des planches 12 et 15 de l'autoroute A2 (BL), le Laboratoire des voies de circulation (LAVOC) a mis en place des capteurs de déformation au sein des couches bitumineuses lors de la pose de mai 2003

Long term effect of modified binder on cracking resistance of pavements

Combined loading and climatic effects associated with the choice of high modulus bituminous mixtures, in order to prevent the pavements from rutting, have increased the risk of cracking failure in the bituminous layers. It was decided, in 1989, to start a long-term assessment of a wide range of new products. Cracking, rutting and ravelling monitoring have been carried out regularly during 14 years of pavement service. 16 test sections of 300 meters were constructed. The structures of all those test sections were identical, except the choice of the wearing course binder for which 12 modified binders, and 4 pure bitumens as reference, were selected. A new assessment method of in situ cracking is proposed which consider the gravity and the extent separately in order to get a cracking amplitude parameter. Distinction has been made between the initiation and the propagation of cracking. In general, PmBs show some improvement of the performance of the wearing course compared to conventional binders. However, one section with direct refining pure bitumen performs as well as some PmBs. Cracking resistance for one section with SBS modified bitumen was tremendous. A large amount of tests have been carried out on the wearing course binders and mixes during the whole monitoring period. It was noted that classical laboratory tests couldn't be used as tools for the long term behaviour prediction. Thorough studies were carried out on the TSRST, the BBR tests

Assessment of the rheological properties of asphalt rubber binder and its residual phases

The asphalt rubber blends design is an empirical procedure and is quite sensitive to the variability of the components properties. A better understanding of the physical phenomenon involved during the curing process is a prerequisite step to propose a rational design procedure. This paper describes results from a laboratory investigation of the interaction between crumb rubber and different composition bitumen. The physical blending of the two components is achieved according to the Wet Process method with different proportions and size distributions of the rubber powder. Rubber particles' swelling in bitumen is assessed thanks to a centrifuging process, allowing a satisfactory separation of the residual bitumen and the rubber particles phases. Rheological measurements are carried out on base components, as well as on the final composite, and its residual constituting phases. The rubber swelling ratio, ranging from 200 to 400%, demonstrates that the final rubber phase is mainly constituted with absorbed bitumen. This phase shows a higher temperature sensitive behaviour slightly different from the one exhibited by the base rubber. The thermal sensitivity is clearly illustrated by the rheological measurements. On the other hand, the residual bitumen shows a significant hardening which is more marked for base bitumen with low aromatic oils content. The proposed experimental protocol improves the knowledge on the interactions in the asphalt rubber blends and could be a basis for a rational design approach