Personne :
Conciatori, David

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Conciatori
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David
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Université Laval. Département de génie civil et de génie des eaux
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ncf11921104
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  • Publication
    Restreint
    Influence of microclimate on the probability of initiation of chloride induced corrosion in reinforced concrete
    (2002-09-01) Conciatori, David
    Two main factors govern the ingress of chloride ions into concrete reinforced with ordinary steel reinforcement, from de-icing salts: (1) the cover concrete (permeability, thickness), and (2) the microclimatic conditions (humidity, temperature, concentration of de-icing salts) at the concrete surface. A numerical model of chloride transport, taking into consideration environmental conditions (temperature, humidity, snow, rain and salt spreading), was used to predict the chloride profiles in concrete representative of that found in bridge element, for two types of exposure to water (splash, mist). This model was applied for two different regions in Switzerland: on the plateau in Lausanne, where there is a relatively mild winter climate and in the Alps where there is severe winter climate.
  • Publication
    Accès libre
    Monitoring of northern climate exposure
    (American Society of Civil Engineers, 2019-08-08) Conciatori, David; Sanchez, Thomas; Kerserle, Gilberto Cidreira
    Currently, facility managers are faced with many advanced decisions regarding when and how to inspect, maintain, repair or renew existing facilities in a costeffective manner. The evolution of the deteriorations of road structures in reinforced concrete depends on the exposure of the elements to water in liquid form or vapour and to other aggressive agents such as chloride. Current models of ionic transport neglect the effect of real ionic concentration in contact with concrete structures, it means boundary conditions are considered with simple tendency as uniform concentration during the winter period and model parameters are derived from the fitting method. Therefore, it implies in ineffective prediction models of deterioration, i.e. steel rebar corrosion by chloride presence or carbonation, alkali-granular reaction, acid attacks, etc. Structure are sensitive to their environment and their interaction with it is directly related to the processes of deterioration. The degradation of structures exposed to salt-laden mist is faster in the wetter areas. On the contrary, the deterioration of the structures caused by salt spray in the drier zone is slower. The structures, exposed to splashing (precipitation, wind, splash, etc.), have a slower rate of degradation in the wetter regions. The amount of rain has an indirect effect in the process of deterioration of the structure exposed to salt-laden mist because it changes the contact time of chloride on the surface of the structures. For this purpose, a unique exposure monitoring was developed. This mobile station, named MExStUL, contains an atmospheric sensor and new possibilities of chloride detection contained in splashes, mist and static water near the road improving the real exposure of structure and the boundary conditions. First results highlight the real influence of environmental parameters on structures durability on highways. Salt concentration is not uniform during winter period and water thickness demonstrate important periods of drying.
  • Publication
    Accès libre
    Comprehensive modeling of chloride ion and water ingress into concrete considering thermal and carbonation state for real climate
    (Elsevier, 2010-01-01) Conciatori, David; Laferrière, Francine; Brühwiler, Eugen
    This article presents a comprehensive modeling of temperature, carbonation, water and chloride ions transport in cover concrete using the transport model “TransChlor”. The TransChlor transport model employs weather data and chloride ion concentrations present on the concrete surface to predict the temporal and spatial evolution of the presence of chloride ion concentrations in the cover concrete pores. The main features of the TransChlor model are presented and validated. The TransChlor model has been calibrated using experimental data on liquid water movement in concrete of different permeabilities under realistic microclimatic conditions. Chloride ion transport is validated by means of experimental results obtained from a newly developed chloride ion optical fiber based sensor.
  • Publication
    Restreint
    Dégradation des structures en condition hivernale et ses limitations
    (2018-05-08) Conciatori, David; Cidreira Keserle, Gilberto
    La dégradation des structures est une problématique constante où les coûts de réhabilitation annuels peuvent atteindre des milliards de dollars en Amérique du Nord. Les coûts indirects, comme les retards dus aux embouteillages et à la perte de productivité résultants de l'entretien des ponts et aux remplacements des structures, augmentent de plus de dix fois le coût direct lié aux détériorations des ouvrages. Des modèles performants permettent de déterminer la durée de vie restante d’un élément ou d’une structure en considérant la résistance des structures à la corrosion et les mécanismes de détérioration de manière quantitative. Ces mécanismes de détérioration dépendent du climat ambiant et de l’environnement qui sont essentiels afin d’établir la fiabilité des méthodes de conception liées à la performance structurale. L’Ontario et le Québec sont les provinces qui utilisent le plus de sel de déverglaçage pour la sécurité des usagers pendant la période hivernale. Ces types de sel contiennent des ions chlore et qui migrent dans la solution interstitielle du béton armé jusqu’au niveau des aciers d’armature et les corrodent lorsqu’ils se trouvent en quantité suffisante. La vitesse de diffusion des ions chlore dépend directement de l’exposition de la structure au climat et au sel de déverglaçage. Cette étude vise à montrer l’influence des conditions environnementales et climatiques dans la dégradation des structures en condition hivernale.
  • Publication
    Restreint
    Comportement à l'effort tranchant et à la flexion des ouvrages en béton utilisant des matériaux à hautes performances
    (2013-08-01) Conciatori, David; Willem, Xavier; Massicotte, Bruno
    Plusieurs poutres de géométrie et de matériaux différents sont amenées à la rupture pour observer leur comportement à la flexion et à l’effort tranchant. Cette observation est faite par l’intermédiaire d’essais en laboratoire et de simulations numériques 3D non linéaires, accompagnée de conseils judicieux pour l’utilisation des matériaux en polymère renforcés de fibres de carbone (PRFC) et des bétons renforcés de fibres (BRF). De plus, ces matériaux sont exploités à leur maximum en les combinant avec une précontrainte adhérente ou non adhérente soit par pré-tension ou par post-tension.
  • Publication
    Accès libre
    Markov chain-based stochastic modeling of chloride ion transport in concrete bridges
    (Frontiers Research Foundation, 2018-03-02) Chouinard, Luc; Conciatori, David; Zhang, Yan
    Over the last decade, there has been an increasing interest in models for the evaluation and prediction of the condition of bridges in Canada due to their large number in an advanced state of deterioration. The models are used to develop optimal maintenance and replacement strategies to extend service life and optimally allocate financial and technical resources. The main process of deterioration of concrete bridges in Canada is corrosion of the reinforcing steel due to the widespread use of de-icing salts. In this article, numerical models of the diffusion process and chemical reactions of chloride ions in concrete are used to estimate the time to initiation of corrosion and for the progression of corrosion. The analyses are performed for a range of typical concrete properties, exposure and climatic conditions. The results from these simulations are used to develop parametric surrogate Markov chain models of increasing states of deterioration. The surrogate models are more efficient than physical models for the portfolio analysis of a large number of structures. The procedure provides an alternative to Markov models derived from condition ratings when historical inspection data is limited.
  • Publication
    Restreint
    Modified chloride migration test on UHPFRC samples
    (BEFIB, 2016-09-19) Conciatori, David; Blais-Dufour, Guillaume; Sorelli, Luca; Corvez, Dominique
    The outstanding tensile resistance of UHPC can effectively reduce the crack openings and the diffusion in a structural element. In service life, this provides finest and more diffuse cracks, which ensure greater durability. Assessing the durability of UHPC with standard techniques (such as, e.g., air permeability test, capillary absorption test, migration test, etc.) is not straightforward as the results are often out of the measuring range. Measurement of chloride diffusion is commonly done for standard concrete with an accelerated migration test (ASTM C1202). When the standard protocol is adopted, the chloride diffusion is so rather negligible and cannot be accurately measured. Thus, such results are cannot give useful information on the possible chloride diffusion process in real field condition, especially when deterioration processes occur. There is today a critical need to set up a laboratory test which can quantify the chloride penetration in UHPC in order to correctly assess on the guaranteed lifetime of a structure. In a preliminary study, this article investigates the suitability of modifications of the standard migration test for UHPC. The effect of the fibre reinforcement on the chloride profiles was also assessed. Finally, the chloride profiles are found to be comparable with five years of UHPC-exposure in an immersed marine environment.
  • Publication
    Restreint
    Simulation of the corrosion behaviour of concrete elements reinforced with high performance steel
    (fib Proceedings, 2001-10-01) Brühwiler, Eugen; Conciatori, David; Denarié, Emmanuel
    The effect, on the chloride-induced corrosion initiation time, of using different grades of reinforcing steel in concrete elements is evaluated. The corrosion initiation times were determined numerically for three types of reinforcement for different combinations of concrete cover quality and thickness, and exposure zone. The results show that high performance steel rebars (i.e. steel with improved corrosion resistance, stainless steel) significantly improve the corrosion resistance of concrete elements.
  • Publication
    Accès libre
    Updating of chloride ingress models using core data measurements
    (Inderscience Enterprises Ltd, 2015-11-20) Wolofsky, Robert; Chouinard, Luc; Conciatori, David; Bastien, Josée
    A large proportion of concrete bridges in North America are reaching the end of their service life. An important factor that accelerates deterioration is the amount of salts used during winter months. The chloride ions from the salt enter the concrete and destroy the passive-oxide layer that protects the reinforcing steel from corrosion. The TransChlor® software is used to simulate the time history of chloride ion ingress into a typical concrete bridge. A climate model is used to simulate the exposure of the structure to winter conditions. A probabilistic method is used to propagate the uncertainty on material properties in the model and to obtain the distribution of chloride ion concentrations. A procedure for updating the distribution is proposed using data from core samples at two depths (25/50 mm) and for the two types of exposure (splash/direct). The procedure is shown to be very efficient in reducing bias and variance from model predictions.
  • Publication
    Accès libre
    Predicting the Shear Behaviour of Solid Slab Bridges using Nonlinear Finite Elements
    (2012-05-30) Conciatori, David; Massicotte, Bruno
    Catastrophic collapse of Concorde Bridge in 2006 near Montreal raised the issue shear stress concentration in straight and skewed concrete concrete slab bridges. These bridge have been traditionally designed without shear reinforcement. Questions were raised concerning the reliability of existing bridges and also on the design guidelines of new bridges. Straight and skewed solid concrete slab bridges are modeled using linear and nonlinear finite element models to highlight shear forces that develop in slab bridges, particularly at the corners. Various types of loads are applied in order to understand the elastic and plastic behavior of the corner force in service conditions and near ultimate. A parametric study is carried out on several configurations of simply supported slabs with geometries covering one to four lane bridges of 3 to 20 m spans and with skew angles ranging from 0° to 60°. The analyses show that comer forces develop locally and the actual design of straight and skew concrete slab bridges is not influenced by the comer forces. A redistribution of corner forces is observed near ultimate limit states with apparition of shear crack bringing ductility at this failure mode. The analyses indicate that these corner forces appear along the free edge with depth about a half-thickness of the concrete slab. This justifies reinforcing the free edge by stirrup, when the design propose a reinforcement. For existing bridges, the analyses show that strength obtained using a beam type behavior is too conservative for estimating the actual shear strength.