Probabilistic and predictive performance-based approach for assessing reinforced concrete structures lifetime: The applet project

International audienceConcrete deterioration results in different damage extents, from cracking to concrete spalling, from losses of reinforcement cross-sections to bond losses. A relevant prediction of this performance is the basis for a successful management of the concrete structures. Conversely, the large amount of uncertainties related to parameters and models require a specific analysis in order to provide relevant results. The APPLET project intends to develop a probabilistic and predictive performance-based approach by quantifying the various sources of variability (material and structure), studying the interaction between environmental aggressive agents and the concrete material, ensuring a transfer of the physical-chemical models at the material scale towards models at the structure level, including and understanding in a better manner the corrosion process, integrating interface models between reinforcement and concrete, proposing relevant numerical models, integrating know-how from monitoring or inspection. To provide answers, a consortium of 19 partners has been established and has promoted a research project funded by the French Research Science Agency (ANR). Started in May 2007, the project has ended in November 2010. This paper will resume the most significant advances targeted by this research project

Electroactive biofilms: new means for electrochemistry

This work demonstrates that electrochemical reactions can be catalysed by the natural biofilms that form on electrode surfaces dipping into drinking water or compost. In drinking water, oxygen reduction was monitored with stainless steel ultra-microelectrodes under constant potential electrolysis at )0.30 V/SCE for 13 days. 16 independent experiments were conducted in drinking water, either pure or with the addition of acetate or dextrose. In most cases, the current increased and reached 1.5–9.5 times the initial current. The current increase was attributed to biofilm forming on the electrode in a similar way to that has been observed in seawater. Epifluorescence microscopy showed that the bacteria size and the biofilm morphology depended on the nutrients added, but no quantitative correlation between biofilm morphology and current was established. In compost, the oxidation process was investigated using a titanium based electrode under constant polarisation in the range 0.10–0.70 V/SCE. It was demonstrated that the indigenous micro-organisms were responsible for the current increase observed after a few days, up to 60 mA m)2. Adding 10 mM acetate to the compost amplified the current density to 145 mA m)2 at 0.50 V/SCE. The study suggests that many natural environments, other than marine sediments, waste waters and seawaters that have been predominantly investigated until now, may be able to produce electrochemically active biofilm

Using contact potential measurements to analyse future intercity links made possible by the Tours–Bordeaux High-Speed Rail line

New high-speed rail transport infrastructures produce profound time-space changes that make new activities possible. Our aim is to measure the impact of such changes on potential business or leisure travel between cities.We develop a contact potential indicator (Törnqvist, 1970) that measures the possibility of making a trip to a distant location within the desirable time-space prism. The indicator is developed in the context of the high-speed rail line between Tours and Bordeaux.The results demonstrate the possibility of contact from a series of key cities affected by new high-speed rail infrastructure, both before and after project completion. Our analysis shows that Bordeaux benefits greatly from the extension of the rail line: the preferred method of contact to Paris will switch to rail from the current air preference, and several cities that cannot be reached in the current pre-project conditions will become “contactable”. Other cities that benefit are Angoulême, Tours and Poitiers.Les nouvelles infrastructures de transport ferroviaire provoquent de profondes transformations de l’espace-temps qui rendent de nouvelles activités possibles. Notre but est de mesurer les impacts de telles transformations sur le potentiel de déplacement pour motif affaires ou tourisme entre villes.Nous développons l’indicateur du potentiel de contact (Törnqvist, 1970) qui mesure la possibilité d’effectuer un déplacement vers un lieu distant dans les contraintes du prisme d’espace-temps de la time geography. L’indicateur est mis en œuvre dans le contexte de l’ouverture de la ligne ferroviaire à grande vitesse entre Tours et Bordeaux.Les résultats démontrent la possibilité de contact entre un ensemble de villes clés affectées par la nouvelle infrastructure de transport rapide, avant et après son ouverture. Notre analyse montre que Bordeaux bénéficie grandement de l’extension de la ligne : le mode le plus favorable pour réaliser le potentiel de contact avec Paris bascule de l’aérien au ferroviaire, et plusieurs villes qui ne pouvaient pas être rejointes dans les conditions précédant la réalisation du projet ferroviaire, deviennent « contactables ». Les autres villes bénéficiaires sont Angoulême, Tours et Poitiers

Micro-Mechanical Analysis of Corrosion Products Formed During Long-Term Carbonation Induced Corrosion of Steel

During corrosion distinct types of corrosion products form, composed of different ratios of ferrous ions and oxide, hydroxides. Corrosion products have different physical and mechanical properties, mainly density, resistivity, volume and modulus of elasticity compared to iron. Knowing properties of corrosion products is indispensable for service life modelling of structures and can give valuable insight into the long-term corrosion propagation process. In this study micro-indentation method was used to evaluate mechanical properties of different layers formed during long-term carbonation induced corrosion of steel in concrete. Investigation was performed on three sets of reinforced concrete samples, that underwent corrosion during 50, 60 and 70 years. Raman microspectroscopy was performed locally to determine and locate the constitutive phases of the corrosion system and to correlate them to the results of micro-indentation. Using grid technique, spatial distribution of phases with different mechanical properties was obtained for samples of different age. Comparison of values of mechanical properties for the same phases obtained on different samples, allowed hypothesis on their long-term behaviour

Nosemosis of honeybees: chronicle of a disappearance in France

La nosémose à Nosema apis est une maladie de l’Abeille mellifère classée danger sanitaire de catégorie 1. Les données épidémiocliniques récentes indiquent une baisse marquée de son incidence au point que d’endémique la maladie pourrait aujourd’hui être requalifiée de sporadique. Parallèlement, de nouvelles techniques analytiques ont permis de montrer que l’agent causal cohabitait depuis peu avec une nouvelle espèce d’origine asiatique, Nosema ceranae . Ces deux espèces aux caractéristiques morphologiques et biologiques proches occupent une même niche écologique : les entérocytes du ventricule des abeilles adultes. L’espèce émergente Nosema ceranae , dont l’infection est plutôt asymptomatique, est aujourd’hui prédominante. La mondialisation des échanges d’abeilles, les bou- leversements environnementaux peuvent être des facteurs essentiels à l’implantation de nouveaux parasites. La disparition progressive de la nosémose en France est un exemple de la complexité des relations hôtes-parasites ainsi que de notre incapacité à prévoir l’émergence d’organismes exotiques.Type-A nosemosis, caused by Nosema apis, is a disease of the Honeybee classified as a notifiable disease in France. Recent epidemioclinic data indicate a marked decrease in its incidence to the point that this endemic disease could now be requalified as sporadic. At the same time, new analytical tech- niques have shown that the causal agent has recently cohabited with a new species of Asian origin, Nosema ceranae. These two species, with close morphological and biological characteristics, cohabit the same ecological niche: the enterocytes of the ventricle of adult bees. The emerging Nosema cer- anae, whose infection is rather asymptomatic, is now becoming predominant. Globalization of bee trade, environmental changes, can be critical factors to the introduction of new pests. The progressive disappearance of nosemosis in France is an example of the complexity of host-parasite relationships as well as our inability to predict the emergence of exotic organisms

MISTeR : Maîtriser l’Information Scientifique et Technique en Recherche : une offre de formation originale pour les doctorants de l’Institut National de la Recherche Agronomique (Inra)

Depuis quelques années, les professionnels de l’information scientifique et technique (IST) font deux constats majeurs : d’une part, les chercheurs accèdent désormais à l’IST directement via le Web et de façon totalement autonome, d’autre part, la recherche, la gestion et la communication de l’IST restent le « parent pauvre » de la formation universitaire française des futurs chercheurs, y compris au sein des écoles doctorales. À l’Inra, comme dans tous les autres organismes de recherche en F..

Detour and break optimising distance, a new perspective on transport and urbanism

International audienceFrom a discussion about the mathematical properties of metrics, we identify three fundamental characteristics of distance, which are optimality, detour and break. We then explore the implications of these properties for transport planning, urbanism and spatial planning. We state that distances contain the idea of optimum and that any distance is associated to a search for optimisation. Pedestrian movements obey this principle and sometimes depart from designed routes. Local sub-optimality conveyed by public transport maps has to be corrected by interventions on public space to relieve the load on central parts of networks. The second principle we state is that detour in distances is most often a means to optimise movement. Fast transport systems generates most of the detour observed in geographical spaces at regional scale. This is why detour has to be taken into account in regional transport policies. The third statement is that breaks in movement contribute to optimising distances. Benches, cafés, pieces of art, railway stations are examples of the urban break. These facilities of break represent an urban paradox: they organise the possibility of a break, of a waste of time in a trip, and they also contribute to optimising distances in a wider network. In that sense break should be considered as a relevant principle for the design of urban space in order to support a pedestrian oriented urban form

Dysplasie de la hanche et moniales cisterciennes : l’exemple de l’Abbaye de Saint Pierre de l’Almanarre (XIIIe-XIVe, Hyères, Var, France)

Les ruines de l’ancienne Abbaye de Saint Pierre de l’Almanarre font partie du site archéologique d’Olbia, forteresse grecque située sur la commune d’Hyères. Si ce secteur fait l’objet d’intenses investigations archéologiques depuis les années 1950, le cimetière attenant à l’abbaye a été fouillé principalement durant les années 1990. Il a livré 495 tombes à la fois de laïcs et de religieuses, regroupées dans un secteur décrit alors comme spécifiquement dédié aux moniales cisterciennes de cette..

Impact of the Erika oil spill on sea birds: review of post-Erika studies

Le Drean-Quenec’Hdu Sophie, L'Hostis Monique. Impact de la marée noire de l’Erika sur les oiseaux marins : bilan des différentes études post-Erika. In: Bulletin de l'Académie Vétérinaire de France tome 158 n°3, 2005. pp. 313-317

Influence of slag composition on the stability of steel in alkali-activated cementitious materials

Among the minor elements found in metallurgical slags, sulfur and manganese can potentially influence the corrosion process of steel embedded in alkali-activated slag cements, as both are redox-sensitive. Particularly, it is possible that these could significantly influence the corrosion process of the steel. Two types of alkali-activated slag mortars were prepared in this study: 100% blast furnace slag and a modified slag blend (90% blast furnace slag? 10% silicomanganese slag), both activated with sodium silicate. These mortars were designed with the aim of determining the influence of varying the redox potential on the stability of steel passivation under exposure to alkaline and alkaline chloride-rich solutions. Both types of mortars presented highly negative corrosion potentials and high current density values in the presence of chloride. The steel bars extracted from mortar samples after exposure do not show evident pits or corrosion product layers, indicating that the presence of sulfides reduces the redox potential of the pore solution of slag mortars, but enables the steel to remain in an apparently passive state. The presence of a high amount of MnO in the slag does not significantly affect the corrosion process of steel under the conditions tested. Mass transport through the mortar to the metal is impeded with increasing exposure time; this is associated with refinement of the pore network as the slag continued to react while the samples were immersed