François Olard

Bio: François Olard is an academic researcher from École Normale Supérieure. The author has contributed to research in topics: Asphalt & Wearing course. The author has an hindex of 21, co-authored 62 publications receiving 1651 citations.

General “2S2P1D” Model and Relation Between the Linear Viscoelastic Behaviours of Bituminous Binders and Mixes

Abstract: A research including a large experimental campaign on the characterization of the viscoelastic behavior of different bituminous materials was developed. The aim is to establish the links between the viscoelastic properties (which are observed in the small strain domain) of binders and those of bituminous mixes. The viscoelastic behavior of bituminous binders and mixes has been studied by performing complex modulus tests at different temperatures and frequencies. A unique rheological model has been developed for the modeling of linear viscoelastic properties of both bituminous binders and mixes. This model consists of a generalization of the Huet-Sayegh analogical model. Analyses on test data for nine different binders and four mixes, with one mix design, show that the introduced model fits quite well the measurements. Finally, from our first results, a transformation that is independent of the introduced model allows to predict easily and efficiently the mix complex modulus from the binder one.

Linear viscoelastic behaviour of bituminous materials: From binders to mixes

Abstract: A large experimental campaign on the characterization of the linear viscoelastic behaviour of different bituminous materials was carried out. The goal was to establish the links between the linear viscoelastic properties (which are observed in the small strain domain) of binders and those of bituminous mixes. The linear viscoelastic behaviour of bituminous binders and mixes was studied by performing complex modulus tests at different temperatures and frequencies. A unique rheological model (called “2S2P1D model”) was developed for the modelling of linear viscoelastic properties of both bituminous binders and mixes. This model consists of a generalization of the Huet-Sayegh analogical model. Analyses on test data for five binders and different mastic and mix composition, show that the introduced model fits quite well the measurements. Finally, from our first results, a transformation that is independent of the introduced model allows the mix complex modulus to be predicted easily and efficiently f...

Three-Dimensional Thermo-Viscoplastic Behaviour of Bituminous Materials: The DBN Model

Abstract: The DBN model, so called from its authors Di Benedetto and Neifar, has been developed, based on simple rheological elements and experimental results on bituminous materials. This model was developed thanks to the large amount of data obtained during the last two decades in the DGCB laboratory. In previous works, the development of the model has been limited to a unidirectional formulation. Nevertheless, the ability of this model to take into account the complex thermo-viscoplastic behaviour of bituminous material in different domains of loading is shown in this paper. In order to simulate the real behaviour in the pavements, the DBN model has been extended to a 3D formulation, which is described in the paper. The calibration of DBN model is also explained. Numerical simulations are compared with some few available data, considering the 3D behaviour of these materials.

Influence of reclaimed asphalt pavement content on complex modulus of asphalt binder blends and corresponding mixes: experimental results and modelling

Abstract: The objective of the presented study is to determine linear viscoelastic (LVE) properties of corresponding binders and mixes and to check how they change with reclaimed asphalt pavement (RAP) content. The investigation is part of a wider on-going research project, in the framework of a PhD thesis, in collaboration between Universite de Lyon/Ecole Nationale Travaux Publics de l'Etat (ENTPE), EIFFAGE Travaux Publics and Beyond Petroleum. Dynamic shear rheometer and tension/compression (using a Metravib device) complex modulus tests were performed on nine different bitumens, produced as blends of two different base bitumens and RAP-extracted bitumen in various proportions. LVE properties of six asphalt mixes, produced with the same materials and proportions of certain bitumen blends among the nine tested ones, were measured in tension/compression mode. 2 Springs, 2 Parabolic Elements, 1 Dashpot model was used to fit experimental data both for binders and mixes. Shift-Homothety-Shift in time-Shift transformation (developed at ENTPE) was applied to verify the correspondence of LVE behaviours of related binders and mixes.

From the Behavior of Constituent Materials to the Calculation and Design of Orthotropic Bridge Structures

Abstract: A new approach is proposed to determine the global response of an orthotropic bridge structure from the behavior of the constituent materials that are binders, aggregates and steel. Experimental results and modeling using constitutive models (2S2P1D and DBN) developed by ENTPE team are presented for the bituminous materials in the linear domain. From these results, a transformation that is independent of the introduced models allows the bituminous mix complex modulus to be predicted from the bitumen complex modulus. Then, the response of a 3D orthotropic steel deck bridge subjected to moving wheel loads is presented using numerical Finite Element Method (FEM). The influence of temperature and viscous behavior of surfacing layers on the structure response such as deflection and longitudinal stress are emphasized.

General “2S2P1D” Model and Relation Between the Linear Viscoelastic Behaviours of Bituminous Binders and Mixes

Abstract: A research including a large experimental campaign on the characterization of the viscoelastic behavior of different bituminous materials was developed. The aim is to establish the links between the viscoelastic properties (which are observed in the small strain domain) of binders and those of bituminous mixes. The viscoelastic behavior of bituminous binders and mixes has been studied by performing complex modulus tests at different temperatures and frequencies. A unique rheological model has been developed for the modeling of linear viscoelastic properties of both bituminous binders and mixes. This model consists of a generalization of the Huet-Sayegh analogical model. Analyses on test data for nine different binders and four mixes, with one mix design, show that the introduced model fits quite well the measurements. Finally, from our first results, a transformation that is independent of the introduced model allows to predict easily and efficiently the mix complex modulus from the binder one.

Warm-Mix Asphalt: European Practice

Abstract: Warm-mix asphalt (WMA) is a group of technologies that allow a reduction in the temperatures at which asphalt mixes are produced and placed. These technologies tend to reduce the viscosity of the asphalt and provide for the complete coating of aggregates at lower temperatures. WMA is produced at temperatures 20 to 55 °C (35 to 100 °F) lower than typical hot-mix asphalt (HMA). In 2007, a team of U.S. materials experts visited Belgium, France, Germany, and Norway to evaluate various WMA technologies through the Federal Highway Administration’s International Technology Scanning Program. The scan team learned that the benefits of WMA technologies include reduced fuel usage and emissions in support of sustainable development, improved field compaction, which can facilitate longer haul distances and cool weather pavement, and better working conditions. A range of technologies is available to produce WMA. European agencies expect WMA performance to be the same as or better than the performance of HMA. Although several areas need to be addressed as these technologies are adapted to U.S. materials and production practices, the scan team believes that the United States has no long-term barriers to WMA use. With additional research and trials, the team expects that highway agencies will allow WMA as an alternative to HMA.