The French national project MURE, a collaborative research and development programme, started in March 2014. Two main issues are addressed: coupling of recycling and warm-mix asphalt technique and multi-recycling of bituminous mixtures. It gathers the national road federation, academic laboratories, road contractors and project contracting officials. The objective of the first working group (WG1) of MURE is to validate an accelerated ageing process for bituminous mixtures as well as on site than in laboratory. To achieve this goal, it is first necessary to characterize the ageing using a reliable and reproducible method valid for laboratory and plant-made mixtures. Many studies from the literature showed the efficiency of FTIR spectroscopy for ageing identification. In particular, carbonyl and sulfoxide groups found in binders are appropriate ageing markers. Meanwhile, no common FTIR protocol does exist at present. The first step of the experimental work performed by the WG1 was to compare seven FTIR methods, differing from sample preparation and approaches for calculating spectroscopic indexes. One given bitumen was aged eight times successively by RTFOT method (75 min-163 °C). Two IR spectrum acquisition modes were tested: attenuated total reflectance (ATR) and transmission (spreading of bitumen on an IR transparent plate and bitumen dissolution in a solvent). The second step of the study was to verify the repeatability of FTIR tests on neat and aged bitumen according to sample preparation and calculation methods. The results allow confirming the relevance of FTIR spectroscopy for qualifying bitumen ageing. A single methodology and a common tool for harmonizing the calculation of indexes are proposed. The whole procedure can be used to follow the ageing properties on site at short and long times.
This paper presents results of laboratory tests on hot and warm bituminous mixtures produced with Reclaimed Asphalt Pavement (RAP). Additives were used to produce warm bituminous mixtures. Fatigue behaviour and thermomechanical behaviour at low temperature were investigated. Fatigue was studied by analysing the tension/compression fatigue test results. Four different failure criteria were used in order to evaluate fatigue life. The low temperature behaviour of the materials was characterized using the Thermal Stress Restrained Specimen Test (TSRST). For each material, three replicates were performed. The experimental device was improved so that radial strains in two directions could be measured during the tests. Tri-dimensional behaviour could thus be investigated. The results of both tests were analysed and the influence of the void content, RAP content, type of additives and manufacturing process was evaluated. The results show that RAP addition and warm bituminous mixtures could be combined to obtain mixtures with performances comparable to classical hot mixtures.
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