[en] The argillaceous materials properties could be favourable to the radioelements confinement in high activity and thermogenic nuclear waste disposal. This study relates to the transformations induced on these materials under thermal stress and the impact on their properties. The samples were collected in the vicinity of a natural analogue: a basaltic intrusion in an argillaceous formation (argillites of Laumiere, Aveyron, France). This volcanic event has functioned for an unreachable time in a laboratory. The study of the mixed-layered illite-smectite minerals (I-S), major minerals of these argillites, shows an illitisation at the basaltic intrusion contact. The thin and disturbed variation of an index of crystallinity of the I-S corresponds to the influence of the geological context. Laumiere highlighted determining parameters (smectite formation during hydrothermal alteration) which has influenced the evolution of argillaceous materials in thermal context. (author)

[en] Natural or engineered clay-rich materials are ubiquitous when it comes to achieving sequestration of acid gas, confinement of pollutants or high level radioactive waste (HLRW), and trapping hydrocarbon oil and gas in geological settings. The sequestration, confinement, and trapping functions rely on properties such as low permeability, high sorption and ion exchange capacity, and, in some cases, on swelling abilities. Clay-rich materials contain specific clay minerals possessing these properties due to the small size and high tortuosity of the pores as well as the very high specific surface area and the surface charge of these minerals (especially smectites). For performance and safety purposes, the persistence of this initial sealing function has to be ensured over time, as the clay minerals of interest and the foreign anthropogenic materials (concrete, steel, and other clay materials in situ) will undergo physicochemical interactions and may lead to irreversible transformations. The clay minerals will also be subjected to perturbations due to the heat release of waste packages in the case of HLRW repository, and liquid water and vapour transfers. To tackle the complexity of these phenomena, we combine multi-scale and multi-technique characterisation (middle and far Fourier transform infrared, X-ray diffraction, scanning electron microscopy (SEM) and transmission electron microscopy (TEM)) on samples coming from laboratory experiments and natural analogues, and integrate the results through reactive transport modelling. As an example, the characterisation methodology is used to establish the illitisation of clay-stones due to a basaltic dyke intrusion. The approach is compared with classical ones and the application to diagenetic clay sequences for petroleum exploration is discussed. We also explore the high sensitivity of smectic (gel phase)/smectite properties as a function of water content/composition and temperature by investigating the interactions between metallic iron and smectitic clays. This comprehensive study reveals an iron/clay mass ratio threshold above which the smectites tend to be altered into 7 Angstroms Fe-rich clay minerals with much lower swelling and cation exchange capacity. With a comprehensive description and understanding, the prediction of the long-term evolution of such systems seems to be at hand. However, modelling the overall behaviour of clay-rich materials remains a difficult task because of the strong, multi-scale coupling between chemical, mechanical and transport phenomena, potentially mediated by a smectitic gel phase. (authors)

[en] Serviceability is an indicator that represents the level of service a pavement provides to the users. This subjective opinion is closely related to objective aspects, which can be measured on the pavement's surface. This research aims specifically at relating serviceability results obtained by a 9-member evaluation panel, representing general public as closely as possible to parameters (particularly of roughness) measured within instruments on 30, 25 and 11 road sections of asphalt concrete, Portland cement concrete and asphalt overlay respectively. Results show that prediction of serviceability is quite accurate based on roughness evaluation, while also revealing that, by comparison to studies in more developed countries, Chileans are seemingly more tolerant, in that they assign a somewhat high rating to ride quality. Furthermore, visible distress does not have a significant influence on serviceability values for Chilean users. A ratio between International Roughness Index (IRI) and Serviceability, as defined by AASHTO, was developed and may be used in this design method. Results for the final pavement condition of urban pavements were obtained (IRI-asphalt final=5.9, IRI-concrete final=8.1). (author)

[en] The survivability of two thermographic phosphors, YAG:Pr³⁺ and SMP:Sn²⁺ ((Sr,Mg)₃(PO₄)₂:Sn²⁺), in a combustion environment is studied in the post-flame regime of a premixed propane/air flame. While the laser-induced luminescence of YAG:Pr³⁺ can be exploited for in situ temperature measurements in the exhaust gas above the flame, there is no in situ detectable luminescence for SMP:Sn²⁺ for any reaction conditions within the stability limits of the flame. The phosphor particles are recaptured above the flame and ex situ analyzed for chemical or structural changes using microscopic analysis (SEM/EDX) and x-ray diffraction. The microscopic analysis of post-flame YAG:Pr³⁺ does not show any alteration, whereas morphology and chemical composition of SMP:Sn²⁺ have been modified upon passing through the reaction zone, which is responsible for the loss of its luminescence properties. (paper)