SCC flow curves from vane geometry rheometer

International audienceThe objective of the present study is to show how recording the changes in the rotation torque according to the rotation speed can lead to identifying a characteristic flow curve for the tested concrete. The concrete rheometer used for the study is composed of a vane tool. The rotation speed of the tool is imposed and the resulting torques are measured. The experimental rotation protocol used in this study corresponds to a rapid speed increase followed by a steady speed then the rotation speed slows down. The evolution of the torque measured as the rotation speed decrease (restructuring phase) is considered as being a succession of stationary states. By considering the fluid equivalent to a Bingham fluid for which the yield stress has already been identified and by using an analogy with a coaxial-cylinders rheometer, relevant relationships between the rotation speed of the vane and the rate of shearing along the tool are identified. Shear stress and shear rate calculations for each value of torque and rotation speed lead to the complete flow curve of the tested fluid. The data treatment method is adjusted to accurately evaluate the parameter linked to the flow stop in the case of a non-nil shear rate when the yield stress is reached. The comparison of the characteristic rheological parameters of SCC obtained from the rheometer and both spreading and V-Funnel tests indicate very satisfactory correlations

Hygrothermal effects and moisture kinetics in a bio-based multi-layered wall:Experimental and numerical studies

International audienceA bio-based multi-layered reference wall has been developed within the framework of the European ISOBIO project. One of the key points of this project was to be able to perform proper simulations of the hygrothermal transfers occurring inside such walls. Previous published investigations, also performed in the framework of this project, have demonstrated that the classic assumption of instantaneous equilibrium between local relative humidity and water content according to the sorption isotherm is not relevant for bio-based porous materials, where, in practice, a rather slow kinetics of sorption occurs. The theoretical background developed in this previous study is used here to determine the kinetic constants of the bio-based construction materials and to perform 1D hygrothermal simulations. The kinetics constants are determined thanks to a 1D cylindrical tool based on the local kinetics approach, validated against several experiments of sorption. Then, heat and hygric transfers recorded on a demonstrator building (The HIVE, Wroughton, UK) are analyzed and are simulated using two modeling tools: TMC based on the Künzel approach and TMCKIN based on the local kinetic approach. From the simulations, the local kinetics improves the small timescale RH dynamics. The comparison with measurements performed in the demonstrator confirms the relevance of the local kinetics approach

A catalogue of Spanish archaeomagnetic data

International audienceA total of 58 new archaeomagnetic directions has been determined from archaeological structures in Spain. Together with five previous results they allow the compilation of the first archaeomagnetic catalogue for Spain, which includes 63 directions with ages ranging between the 2nd century BC and the 20th century AD. Characteristic remanence directions have been obtained from stepwise thermal and alternating field demagnetization. The hierarchical structure has been respected in the calculation of the mean site directions. Rock magnetic experiments reveal that the main magnetic carrier is magnetite or titanomagnetite with different titanium contents. The age estimate of the studied structures is generally well justified by archaeological constraints. For six structures the proposed date is also supported by physical methods. The data are in close agreement with the French secular variation (SV) curve. This catalogue represents the first step in the construction of a SV curve for the Iberian Peninsula, which will be of much use in archaeomagnetic dating and in modelling of the Earth's magnetic field in Western Europe

Updated Iberian archeomagnetic catalogue: new full vector paleosecular variation curve for the last three millennia

In this work, we present 16 directional and 27 intensity high‐quality values from Iberia. Moreover, we have updated the Iberian archeomagnetic catalogue published more than 10 years ago with a considerable increase in the database. This has led to a notable improvement of both temporal and spatial data distribution. A full vector paleosecular variation curve from 1000 BC to 1900 AD has been developed using high‐quality data within a radius of 900 km from Madrid. A hierarchical bootstrap method has been followed for the computation of the curves. The most remarkable feature of the new curves is a notable intensity maximum of about 80 μT around 600 BC, which has not been previously reported for the Iberian Peninsula. We have also analyzed the evolution of the paleofield in Europe for the last three thousand years and conclude that the high maximum intensity values observed around 600 BC in the Iberian Peninsula could respond to the same feature as the Levantine Iron Age Anomaly, after travelling westward through Europe

Fire protection of concretes: Formulation, performances and pathology

International audienceThe efficiency of thin mineral passive fire protection layer applied on concrete is analyzed. The more suitable fireproofing material formulations are selected from results of laboratory scale fire test. Such tests consist in the direct exposure of protected concrete samples to the flame of a burner, at constant temperature (850°C). Various formulations of mineral fireproofing materials have been tested to identify the effects of binder type and the density. Formulation compromises are highlighted regarding requested fire performances. Selected formulations are used to protect real scale concrete slab exposed to standard fire (ISO 834). During the test, the concrete/fire protection layer interface temperature and the steel reinforcement temperature have been recorded. For small size slabs, fire proofing layer is completely efficient. The temperature increases are strongly delayed. For large size slabs, delamination of fire proofing layer appears, leading to rapid concrete degradation. To understand the mechanics of cracking and delamination of fire protection layer, laboratory scale tests are performed with two selected formulations varying the implementation methods (surface treatment of concrete, intervention on interface roughness, precracking). It appears that the occurrence of fire protection layer delamination can be avoided choosing the optimal implementation method without adjustment of the optimized formulations. From the 8th International Conference on Concrete under Severe Conditions - Environment and Loading, CONSEC 201

Remontée d’un anneau de voussoir : modélisation et analyse paramétrique

Les mortiers de bourrage injectés entre le sol et l’anneau de voussoirs en béton armé d’un tunnel s’apparentent à des fluides à seuils. L’anneau de voussoir peut, en fonction des sollicitations mécaniques qu’il subit, se déplacer au sein de ce fluide. La modélisation d’un tel problème d’écoulement de fluide plastique permet d’estimer les efforts nécessaires à la mise en mouvement du tunnel dans une direction quelconque ou d’évaluer le risque de remontée d’un anneau de voussoir soumis à un effort de type « poussée d’Archimède ». A cette fin, un outil de calcul analytique est développé. L’incidence des paramètres géométriques, rhéologiques et tribologiques sur les risques de mouvement de l’anneau est alors étudiée. Les résultats obtenus sont comparés à ceux provenant d’un calcul par éléments finis

Navigating pre-hospital end of life care: A paramedic perspective

End of life care (EoLC) issues in the Canadian healthcare system are now commonplace. Palliative care and medical assistance in dying (MAID) programs are giving patients more options than ever before. Consequently, pre-hospital and community paramedicine programs now interact with more patients who require EoLC. This creates ample opportunity for combined growth in the areas of paramedic practice and patient autonomy. This opportunity for growth is not without caveats however. Paramedics now have a responsibility to both further educate themselves and their patients as they increasingly engage with EoLC issues

De l’intérêt d’une caractérisation rhéologique empirique et relative

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