European refining, French in particular, is currently going through a phase of rationalization and search for maximum flexibility in crude supplies. For users of bitumen, this creates concerns about the quality and consistency of products delivered, especially as the European standard EN 12591 appears to them as insufficient to ensure satisfactory performance of the finished products, particularly in the case of specialty products such as high modulus asphalt, polymer modified bitumen, and bitumen emulsions. In this context, the search for correlations between bitumen properties and the performance of the finished product is more relevant than ever. The study presented here is focused on asphalt made with pure bitumen. It was based on a standard design, but with two different types of aggregates. After a preliminary selection, 8 bitumen (20/30, 35/50 and 50/70 pen. grades) were selected. The characterization of asphalt mixes covers all the usual characteristics (stiffness modulus, resistance to rutting and fatigue, resistance to thermal cracking, water sensitivity). The characterization of binders, besides conventional testing, includes the rheological properties (DSR, MSCR, and BBR tests) and the compositional analysis, particularly infra-red spectroscopy and SARA analysis. These tests were performed on the original binders, after RTFO, after RFFO + PAV as well as on the binders recovered from asphalt. This project was conducted as a collaboration between Eurovia and the Western Research Institute (WRI) which performed the compositional analysis of binders, including the SAR-AD™ (WRI improved SARA separation technique) and the chemometrics analysis using their software ExpliFit™.

Since the beginning of 2000's, the development of WMA, Warm Mix Asphalt, allowed the Road companies to meet expectations regarding sustainable development by lowering the fabrication and laying temperatures (reduction of 30 to 50°C). However, this development also highlighted, on the jobsite, an unidentified problem with HMA, Hot Mix Asphalt: a lesser workability during mechanized and especially manual laying, for several WMA processes. This experimentation, part of research thesis results, aims to study the development of a relevant and discriminating test for the evaluation in laboratory of the workability of bituminous asphalt. Two ways were explored; the one uses a classic equipment of road laboratories, the GSC, Gyratory Shear Compactor test, by varying the parameters (vertical strength, rotation speed); the other one is based on the use of the workability device called "Nynas", from now European standardized, with varied parameters. The work was conducted on the same classic asphalt formula with different bitumen grades, and variable temperatures of manufacturing. This parametric study allowed, first of all, to confirm the reduction in workability of asphalts with the reduction in the temperature of manufacturing. It showed the limits of the GSC, a very good test for compactibility but not for workability of asphalt. It also highlighted the interest of the Nynas workability device after a good choice of test parameters for a real relevance of the test result.

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To conserve natural resources and reduce greenhouse gas emissions, the use of Reclaimed Asphalt Pavement (RAP) becomes essential. In order to allow an increase of the RAP content in our bituminous mixtures without affecting either sustainability or the mechanical performance, a lot of research is conducted by the road building companies. A key point lies in a thorough knowledge of the bituminous mix (physico-chemical properties, homogeneity) obtained by blending new and aged bitumen (i.e. recovered bitumen coming from the RAP).These parameters will be affected by the mode of incorporation of RAP and therefore the type of mixing plant. At the same time, new techniques are being developed to reduce the temperature at which asphalt concretes are produced, from 30 to 50°C. This decrease in temperature directly affects the viscosity of the bitumen and therefore also the kinetic of remobilization (bitumen blending). The simultaneous goal of increasing the rate of RAP and reducing production temperature leads to technical limitations undefined to date. Through some examples, this paper presents a methodology to describe the remobilization of different bitumen, to predict the mechanical properties of recycled asphalt, to adjust the asphalt concrete parameters more precisely for future production and asphalt design. The first part presents a new procedure to describe the blending between the aged (RAP) and the new bitumen. It allows a progressive extraction of the bitumen from asphalt with a specific solvent followed by physico-chemical analysis of these samples (leachate). In the second part, a rheological model of modulus prediction of the asphalt concrete specifically developed from the rheological properties of the bitumen and volume distribution of the constituents of the asphalt concrete will be presented.