How can the road construction domain contribute to the CE concept

Over the last century, our society has been set up on a linear economic system that, based on the concept «make, take and dispose», has promoted an unsustainable development and use of natural resources. In recent years, this has led to a change of paradigm by targeting a more circular approach to meet the increasing environmental requirements dictated by the net-zero emissions goal of 2050. Thus, under the pressing needs for a transition to a more sustainable socio-technical system, the circular economy (CE) concept has gained in popularity

Évaluation des performances et des impacts des enrobés bitumineux tièdes

By decreasing the mixing and laying temperatures, warm mix asphalts (WMA) allow a reduction of the energy consumption as well as the emissions, thus contributing to the sustainable development. However researches are necessary for these asphalt mixtures to be considered as a credible option to hot mix asphalts (HMA). The experience regarding mixture behavior is limited and some critical or unverified parameters have to be assessed. Besides, a tool assisting in the choice of the most adapted technology is also necessary. The first research phase consists in a detailed analysis of the mechanical performances from a representative selection of warm mix asphalts. The mix viscosity has been first evaluated, in particular by focusing on the bitumen and mastic behavior. Then, the evaluation of the characteristics and performances have been devoted to the potential critical parameters, with a special emphasis on the performance increases process during the first three months after production and on the samples storage conditions. The results highlight the high performances of WMA containing Fischer-Tropsch wax in the rutting susceptibility temperature domain. The low temperature behavior of this WMA is however more brittle than the reference hot mix asphalt (HMA). WMA with chemical additive (surfactants) shows performances comparable to the reference HMA while the mixture with moisture control proves to have lower mechanical performances in particular due to the reduced ageing of its binder. The various tests performed do not highlight any significant performance increases of the tested mixtures. Moreover, confining the samples in plastics bags does not seem to affect the asphalt mixtures mechanical behavior. In a second phase, an indirect tensile test has been setup and assessed. This test offers a relevant and efficient alternative to traditional complex modulus test on trapezoidal samples, allowing determining the secant modulus of an asphalt sample. A detailed analysis as well as the realization of various tests on asphalt mixtures highlighted some research strands in order to improve the reliability and further develop the testing method. A multi-attribute evaluation methodology of asphalt mixtures has been proposed in the third phase of the research. Various greenhouse gas and energy consumption calculators allowing a comparison of different road projects exist. However, despite the important effect of the asphalt mixture type on the energy consumption and emissions, few of these tools are able to perform a comparison at the asphalt mixture scale. The performances and other qualitative aspects are also not considered. The proposed multi-criteria model takes into account emissions, energy consumption and economical aspects over the whole life cycle of the asphalt mixture. The mechanical performances are also taken into account in the decision process; the databases being provided by the first two phases of the present research. The developed and implemented methodology contains four distinct levels. In the first two levels, some graphical analyses allow identifying the dominant processes and the potential alternatives outranking. The preference and some qualitative criterions are introduced from the third analysis level where a partial aggregation method using pseudo-criterions is proposed. In the last analysis level, data uncertainty and unknown data are considered through an innovative method. To achieve this, a complete aggregation method based on an algorithm derived from the Evidential reasoning approach is selected. The final multicriteria evaluation method proposed offers a pertinent, flexible and robust tool that helps in improving the decision process and thus encouraging innovation

Creating a connection between asphalt wearing surface and timber bridge decks

Timber bridges are increasingly popular again in infrastructure networks nowadays. Protection of timber structural elements from direct exposure to rain and sun is essential to prevent biological degradation of the wood material when using softwoods. In case of a timber deck, the asphalt wearing surface must be water-tight. Creating connected layups has advantages over layups where the asphalt is not connected as traffic loads are transmitted directly to the bridge deck: asphalt surfaces can be loaded with heavier traffic, slopes of bridges can be higher, breaking and acceleration loads are directly transmitted to the bridge deck, and fatigue life of the asphalt is improved. The Swiss standard VSS 40 451 standardized an unconnected mastic asphalt surfacing on timber bridges. Research project VSS 2016/326 was performed to investigate road layups where asphalt wearing surfaces were connected to the bridge deck. This work presents only a part of the results, focused on the bonding issues. Results show that such a layup proves to deliver satisfactory performances, and that shear capacity is comparable to that of concrete and steel decks. Good surface qual-ity of the timber deck is important before application of the bonding agent to avoid short term blistering of the asphalt

Développement durable dans les infrastructures de transport

Depuis la crise climatique des années 1970 et le protocole de Kyoto en 1997, et avec la prise de conscience croissante du changement climatique, les spécialistes des infrastructures de transport ont cherché à innover afin d’économiser les ressources naturelles et de réduire la consommation d’énergie et les émissions pour la construction des chaussées

Decision aid model for asphalt mixture choice

Warm Mix Asphalt (WMA) represents widely used alternative to hot mix asphalt (HMA), this in order to decrease the energy consumption and environmental load. Numerous WMA products can be found and the choice of the most favourable mixture is not necessarily straightforward. In order to achieve this, an innovative methodology has been developed. This methodology permits to consider various qualitative and quantitative criteria such as mechanical performances, production complexity and sustainability, but also includes a life cycle analysis of the emissions (greenhouse gas), energy and costs.The process as developed and implemented comprises four independent levels, each bringing its own contribution to the decision making procedure. The model finally proposed permits to compare different types of asphalt mixtures and assists in a very flexible way in the decision making process