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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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Résultats de recherche

Voici les éléments 1 - 10 sur 10
  • PublicationRestreint
    Chloride penetration model considering the microclimate
    (American Society of Civil Engineers, 2012-04-26) Conciatori, David; Denarié, Emmanuel; Sadouki, Hamid; Brühwiler, Eugen
    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.
  • PublicationAccès libre
    Capillary suction and diffusion model for chloride ingress into concrete
    (Elsevier Science, 2008-08-08) Conciatori, David; Sadouki, Hamid; Brühwiler, Eugen
    A numerical approach, named TransChlor, is proposed to simulate transport phenomena of various substances in concrete. This approach is a theoretical model based on finite elements and finite differences methods. The model consists of coupled nonlinear partial differential equations based on Fick's diffusion law and on kinematics equations. Simulation results from a parametrical study highlight the influence of microclimatic conditions, exposure to deicing salts and concrete cover permeability and thickness on chloride ingress in concrete. The results show that the chloride ion concentration increases quickly in concrete cover when a structure is exposed to deicing salts at a mountainous location; whereas permeability of concrete cover is an insignificant parameter when the concrete is in direct or splash water contact.
  • PublicationAccès libre
    Numerical simulation of the probability of corrosion initiation of RC elements made of reinforcing steel with improved corrosion performance
    (Taylor & Francis, 2018-03-19) Conciatori, David; Brühwiler, Eugen; Linden, Christian
    Steel reinforcing bars in concrete are protected from corrosion by a thin oxide film that is created on the steel surface in the highly alkaline environment of the concrete. Corrosion process begins once this oxide film is destroyed, for example, by chloride ions penetrating from the element surface into the concrete and to the steel rebar. Critical chloride concentration is highly variable owing to numerous factors such as the type of reinforcing steel used. The TransChlor® software is used to simulate the time history of chloride ion ingress and corrosion initiation into a typical reinforced concrete structural element with four different types of reinforcing steel, namely, carbon steel, ferritic stainless steel (1.4003) with rolling skin, duplex stainless steel (1.4462) and ferritic stainless steel (1.4003) with pickled surface. A climate model is used to simulate two different exposure conditions of the structural element, namely direct and mist exposure, representatives for winter conditions in mountainous and lowland areas. A probabilistic method is applied to consider uncertainty of material properties in the model. The results show that reinforcing steel bars with enhanced corrosion performance significantly improve the durability of reinforced concrete.
  • PublicationAccès libre
    Brine absorption in concrete at low temperature – experimental investigation and modeling
    (American Society of Civil Engineers, 2011-06-01) Conciatori, David; Brühwiler, Eugen; Gysler, Roland
    An experimental campaign supports a model named TransChlor for bringing liquid water moved by capillary suction and chloride ions into concrete. The principal objective of the experimental campaign is to represent conventional concretes under real conditions of a local microclimate. Capillarity tests were performed on specimens of three different types of concrete dried at different levels of relative humidity at low temperatures (to −20°C ) to represent the effect of a real climate in winter. This article shows that low temperatures decrease water absorption by capillarity. The use of TransChlor to simulate liquid water and chloride ion penetration into concrete is presented with an emphasis on the faster transport mode of chloride ions by convection when water is in contact with concrete.
  • PublicationAccès libre
    Water absorption in concrete at low temperature
    (RILEM Publications, 2006-09-01) Conciatori, David; Brühwiler, Eugen
    The steel reinforcement corrosion in reinforced concrete elements is the primary cause of rehabilitation interventions on concrete structures. In the domain of highway structures, the majority of corrosion is initiated by the presence of chloride ions introduced by winter deicing salts. The deterioration evolution of highway structures therefore depends on the structure's exposure to liquid water or water vapour containing dissolved aggressive agents like chloride ions. It has been demonstrated, the deterioration evolution rate is quicker for zones in direct contact with liquid water containing aggressive agents than in other zones not in contact with water. This paper presents laboratory tests to quantify the liquid water movement in cover concrete as a function of low temperature to determine the extent of water and chloride ion transport. The principle objective of this experimental campaign is to assess the durability of conventional structural concrete and to analyze the influence of the local microclimate conditions. Low temperature capillary tests have been conducted on various concrete test samples with different permeabilities. The concrete mixtures tested can be separated into three distinct groups based on the water to cement ratio employed, respectively 0.42, 0.52 and 0.73. The permeability of the samples was measured by air permeability and electrical resistivity tests. Prior to conducting the capillarity tests, the samples were dried to three different humidity levels, specifically, 25%, 50% and 75% relative humidity. Following the drying process, the test elements were placed in a freezer until they reached the desired temperature. Finally the capillarity tests were conducted by submerging the specimen in a low-temperature high-concentration salt solution bath at four specific temperatures, -20°C, -10°C, 0°C and +10°C.
  • PublicationRestreint
    Air permeability measurements for the assessment of the in situ permeability of cover concrete
    (Taylor & Francis, 2005-11-01) Denarié, Emmanuel; Conciatori, David; Maître, M.; Brühwiler, Eugen
    The durability of reinforced concrete members depends mostly on the permeability of their cover concrete. The quality of cover concrete largely depends on the conditions of its application (type of formwork, placing, curing, etc.). Thus, the cover concrete properties relevant for a realistic assessment of the durability, and for the owner of the structure, can only be determined on structural members, after the construction process has taken place. With this aim in view, a research and application program has been conducted to provide the methodology for the implementation of the air permeability measurement (Torrent method) as a standard in-situ test. The effects of age, concrete quality, and formwork on air permeability were studied in the laboratory. The statistical variability of air permeability was characterized for 3 laboratory concretes and one site concrete. Probabilistic compliance criteria and a methodology for the assessment of in-situ characteristics of cover concrete were proposed.
  • PublicationAccès libre
    Calculation of reinforced concrete corrosion initiation probabilities using Rosenblueth method
    (Inderscience, 2009-10-01) Conciatori, David; Brühwiler, Eugen; Morgenthaler, Stephan
    The Rosenblueth method is used to analyse stochastic parameters in a numerical model to calculate the solution for independent variables. By replacing all or a part of the independent variables with random variables, the solution becomes itself random. The Rosenblueth method simplifies this passage, while being limited to dichotomous random variables. This avoids the complex and computer-intensive Monte Carlo simulation method. A specific example is developed in this article using a non-linear transport model to simulate chloride ion penetration into reinforced concrete and to predict the development of corrosion in the civil structure. The taking into consideration of complex physical chemical processes and a reconstituted climate increases considerably the simulation time, making impossible the usual use of the Monte Carlo method. The two numerical examples show that the exposure degree affects in a dominating way the appearance of structural damage.
  • PublicationRestreint
    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.
  • PublicationAccès libre
    Actions microclimatique et environnementale des ouvrages d’art routiers
    (Canadian Society for Civil Engineering, 2009-04-07) Conciatori, David; Brühwiler, Eugen; Dumont, André-Gilles
    Les différentes zones d’un ouvrage d’art routier sont étudiées en fonction de leur degré d’exposition au microclimat environnant. Les conditions climatiques provenant de stations météorologiques et la cinétique des véhicules permettent de définir des zones d’exposition aux produits salants et au climat. Une division judicieuse d’un ouvrage en éléments structuraux en fonction de son exposition permet de prendre en considération l’importante variabilité spatiale et de définir des zones de sensibilité équivalente face aux détériorations. Sur la base de stations météorologiques suisses, d’un monitoring d’un ouvrage d’art routier, d’enquêtes auprès des autorités publiques, de mesures ponctuelles in situ et de recherches bibliographiques, cet article met en exergue le microclimat des structures de manière précise. Cette approche permet de définir les différentes zones d’exposition des ouvrages, à savoir les zones de brouillard salin, d’éclaboussures et de stagnation d’eau et de définir l’importance du microclimat en vue de prédire l’évolution des détériorations des structures.
  • PublicationAccès 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.