Nicolas Bueche

Impact of different ageing levels on binder rheology

This paper evaluates the variability of binder rheology for different ageing levels and the influence of ageing at different testing temperatures. Three different ageing levels were applied on a single type of bitumen with a penetration grade of 70/100.The artificial ageing of the binder was performed using the rolling thin-film oven test and the pressure ageing vessel. The rheological behaviour was investigated at low temperatures with the bending beam rheometer (BBR) and at medium and high temperatures with the dynamic shear rheometer (DSR). Several experiments were conducted to determine the range of stiffness and complex modulus results, the type of distribution comparing real and theoretical models, and the effects of ageing on the variability of the rheological behaviour. It was shown that not only the mean results from BBR and DSR tests change with ageing, but also the variability of the results changes with ageing. This would have an impact on mechanistic-empirical pavement design because it would influence the calculated stresses and strains as well as the calculated reliability.

Asphalt Mixture with RAP: Mix Design Optimization

The addition of reclaimed asphalt pavement (RAP) in hot mix asphalt is now common practice in Switzerland. With the increases of RAP content in asphalt mixture, the problematic of the mix design optimization becomes an important issue to be considered. The described project deals with the mix design optimization of hot mix asphalt containing 40 % RAP. In a first phase, an analytical mix design has been conducted. The use of such a numerical method presents in particular the advantages of optimizing laboratory testing and allowing the realization of sensitivity analysis. An extensive laboratory study has been conducted in a second phase. This study permitted to clearly identify and quantify the impacts of the aggregates quality and binder content on the final mixture performances. The various tests achieved highlighted that rutting susceptibility is one of the suitable indicators for the assessment of a mix design performances. The research carried out finally permitted to highlight the benefits of an analytical mix design in a mixture optimization process. The major factors influencing the mix design have been identified and quantified through laboratory testing and some recommendations concerning the tests to carry out are also provided.

Instrumentation and in-situ evaluation of warm mix asphalt test sections

Warm Mix Asphalt (WMA) is widely considered as a potential alternative to conventional Hot Mix Asphalt (HMA) that enables reducing the environmental impacts of the road construction phase. Thus, an ambitious project dedicated to WMA has been launched in 2011 by the Federal Roads Office (FEDRO). The PLANET (PotentieL et ANalyse des Enrobés Tièdes) project contains a specific work package dedicated to the construction, monitoring and evaluation of four different WMA test sections in addition to a reference HMA. The tested techniques involved chemical additives, the uses of zeolite as well as bitumen foaming. RAP addition has also been considered. Several in-situ testing have been conducted in order to compare the WMA techniques. To do this, the test sections have been instrumented using strain gauges and temperature sensors and two measurements campaigns performed with a control truck load. The pavement bearing capacity has also been analyzed through falling weight deflectometer (FWD) measurements. Besides, an extensive laboratory testing campaign has been conducted on the asphalt mixtures and cores taken after different periods of time in order to assess a potential evolution of some mechanical properties or characteristics. The obtained results permitted to highlight the differences between WMA techniques as well as providing good practice guideline for future applications.

Mechanical properties and quality-control of warm asphalt

The aim of the research project PLANET is to provide road experts with technical know-how for the production of bituminous mixtures and paving with low energy and environmental impacts. In this paper the objectives are to assess the methods of control that are usually applied to hot mixes and to make an in-depth study of the mechanical behaviour of the different warm-asphalt technologies in comparison with a similar hot mixed asphalt. Five test fields with 4 different warm-asphalt technologies and one with hot mix-asphalt have been realised. The mixing and laying procedures has been fully documented and the methods of quality control that are usually used were applied. For this purpose a protocol of preparing the sample in the laboratory has been established. A huge amount of samples and cores were tested by different test methods, such as interlayer bonding, rutting test, uniand triaxial cyclic compression test, water sensitivity, fatigue, modulus of elasticity, and indirect tensile test at different temperatures. To assess the time-depended increase of the interlayer bonding a laboratory test-program has been run. The results will be presented and discussed.

Double coating of full depth reclamation materials

Full Depth Reclamation (FDR) and Cold In-Place Recycling (CIR) are popular rehabilitation techniques for flexible pavement. Both techniques can be done with the addition of asphalt emulsion or foamed bitumen as a stabilizer. In most cases, those two techniques to add bitumen are considered equivalent, even if the way they give cohesion to the mix is different. A research project was undertaken to verify the possibility of using both asphalt emulsion and foamed bitumen on FDR materials to have better mechanical characteristics since it’s believed that asphalt emulsion gives a good coating, and foamed asphalt does not coat as well but serves as a binding agent. FDR mixes were prepared in the laboratory with and without asphalt emulsion and foamed bitumen. Different addition processes were tested in order to find the optimum mix design procedure. Moisture susceptibility tests (Marshall tests and indirect tension tests) and complex modulus tests were performed on the different mixes, and it was shown that the use of both binders can give you a mix with better performance. This paper presents the mix design, the test program and the results of this study.

Facilitating the adoption of sustainable technologies in the asphalt sector

A need exists to bridge the gap between innovation in the bituminous materials sector and adoption of the new technologies by national road administrations (NRAs). The Evaluation and Decision process for Greener Asphalt Roads (EDGAR) enables NRAs to do this by providing an assessment methodology which makes sustainability information on new technologies readily accessible to the decision-making process, and therefore facilitates quick adoption of the technologies that offer the greatest sustainability benefits for the highways sector and society as a whole. EDGAR commenced with a wide-ranging review of the range of ‘green’ technologies in the bituminous materials sector and the sustainability benefits that they offer. Two methodologies to assist NRAs were then devised. The first acknowledged that the ability to recycle asphalt is its foremost environmental attribute, and devised a quick, qualitative method for the assessment of recyclability. The second devised a methodology for a more detailed assessment of the sustainability of any bituminous technology, considering all three facets of sustainability: environmental, social and economic, with particular attention given to how the information might be used in the decision process by NRAs, and the common challenges they might encounter when assessing a ‘novel’ technology.