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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 - 6 sur 6
  • 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.
  • PublicationRestreint
    Chloride diffusion in cement materials at different leaching states : an experimental and numerical study
    (American Society of Civil Engineers, 2019-08-08) Henocq, Pierre; Conciatori, David; Aït-Mokhtar, K.; Sanchez, Thomas; Millet, O.
    Due to common heavy snowfall in winter, concrete structures in cold countries are regularly in contact with water. Hence, concrete undergoes abnormal leaching of ionic species present inside the liquid pores of the material. The leaching slowly degrades the structures and may have an influence on the diffusive properties of the chloride ions, coming from the de-icing salts and responsible for the corrosion of the steel reinforcements present in the reinforced concrete. In this work, an experimental and numerical study is propounded to better understand the influence of the leaching state of cementitious material on the diffusive behaviour of chloride ions. Natural and accelerated diffusion tests were performed on samples of hydrated cement paste and concrete samples with lower chloride concentrations (50 mol/m3). The materials were conserved at different leaching state with care not to degrade the microstructure: safe (S), partially leached (PL), and leached (L). The simulation of those various tests was carried out on the reactive transport software PhreeqC to quantify the chloride diffusion. This numerical model allows distinguishing the influence of the geometry of the material (porosity, tortuosity, constrictivity…) to the chemical reactions occurring between chloride ions and the cementitious phases. It then appeared that chloride ions do not diffuse in the same way depending on the leaching state of the cementitious material. Same observations are made on hydrated cement paste and concrete samples. In a safe material, the chloride ions diffuse slowly than in a leached material. It seems not to be due to the material geometry nor chemical reactions. The numerical model developed confirms this hypothesis as it allows to distinguish and quantify their both influence on the chloride diffusion. This study, therefore, highlights the importance of considering the leaching effects in the prediction model for concrete structure durability in cold countries.
  • PublicationRestreint
    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.
  • PublicationRestreint
    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.
  • PublicationAccès libre
    A modified accelerated chloride migration tests for UHPC and UHPFRC with PVA and steel fibers
    (Elsevier, 2018-12-20) Provete Vincler, Juliano; Sanchez, Thomas; Conciatori, David; Turgeon, Vicky; Sorelli, Luca
    Accelerated migration tests which are commonly used to measure chloride diffusion in ordinary cement-based materials cannot be directly applied to composite with very low permeability, such as Ultra High-Performance Fiber Reinforced concretes (UHPFRC). In order to assess the UHPFRC enhancement on the structural durability, there is a critical need to accurately assess the permeability level of the material to chloride ions. The objective of this work is to adapt an existing set-up of accelerated chloride migration test in order to (i) better characterize the resistance of chloride ion penetration in UHPFRC; and (ii) to compare the resistance of chloride ion penetration between UHPC and UHPFRC. The material characterization, the set-up modifications of the existing accelerated migration test, the results are presented. In conclusion, the modification of the test-set-up allowed to accurately measure chloride transport of very low permeability UHPFRC and to shed light on the effect of the fiber reinforcement.
  • 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.