Personne :
Marchand, Jacques

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Marchand
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Jacques
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Université Laval. Département de génie civil
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ncf10274422
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2007 - 200922010 - 20142
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  • Publication
    Restreint
    Sensitivity analysis of the parameters used in a multiionic chloride ingress model
    (RILEM, 2008-10-01) Conciatori, David; Samson, Éric; Marchand, Jacques; Gaudry, Marc J. I.
    A sensitivity analysis of the parameters involved in a multiionic reactive transport model that can be used, among other applications, to predict chloride ingress in concrete structures is presented. The analysis is based on the calculation of the elasticity of each parameter using a rigorous mathematical method. It was performed for two different test cases. The first concerns the penetration of chloride ions in saturated concrete during a simple ponding experiment while the second one involves the influence of wetting and drying cycles on chloride ingress. The analysis indicates that porosity and tortuosity (i.e. ionic diffusion coefficients) are the material parameters which have the most important impact on the model predictions. Boundary conditions were also found to have a significant influence on the output of the model. On the other hand, simulations were found to be much less affected by parameters such as the initial pore solution chemistry and the initial solid phase content of the hydrated cement paste.
  • Publication
    Restreint
    Conception avec prise en compte de la corrosion
    (2007-05-01) Jolin, Marc; Bissonnette, Benoît; Conciatori, David; Marchand, Jacques
    La corrosion des barres d'armature est la première cause des interventions de remise en état sur les ouvrages en béton armé. Dans le domaine des ouvrages d'art routiers, cette corrosion est initiée dans la majorité des cas par la présence de chlorures provenant des produits salants utilisés pour déneiger les routes en hiver. Alors que le phénomène de corrosion en présence d'ions chlorures est relativement bien connu, l'effet du microclimat et l'importance de l'exposition d'un élément en béton armé sur le transport des ions chlorures à travers le béton d'enrobage ne sont pas encore bien compris et modélisés. Plusieurs modèles permettent aujourd’hui de décrire l’évolution physico-chimique d’agents agressifs dans le béton armé et leur interaction avec l’eau et la température, et donc de prédire l’évolution des détériorations. L’aspect non déterministe de la problématique de la corrosion peut également être pris en considération dans ces modèles complexes et donner une idée sur l’incertitude d’apparition de dégâts structuraux. Cette évaluation plus fine des risques de détérioration par corrosion permet de constituer une base objective de dimensionnement à la corrosion, de discussion et de concertation entre maîtres d'oeuvre et spécialistes de la maintenance des ouvrages.
  • Publication
    Accès libre
    Sensitivity of chloride ingress modelling in concrete to input parameter variability
    (SpringerLink, 2014-06-29) Grégoire, Étienne; Chouinard, Luc; Conciatori, David; Samson, Éric; Marchand, Jacques
    The Rosenblueth point estimator method is used to propagate uncertainty on stochastic parameters in a multi-ionic reactive transport model for concrete degradation. The degradation mechanism that was analysed is the ingress of chlorides into concrete. This point estimator method is used because it requires a minimum number of simulations to compute means, standard deviations and skewness for the solution of the transport model. Two exposure cases are considered in this article: the first is a saturated case, and the second is an unsaturated case with wetting (4 days) and drying (3 days at 50 % relative humidity) cycles. The sodium chloride exposure during the wetting cycle of both cases was 500 mmol/L. In both cases, predictions from the model were compared to experimental results. The Rosenblueth approach yielded results comparable to Monte Carlo simulations for both saturated and unsaturated cases. The relative sensitivity of model parameters on prediction results are investigated through a sensitivity analysis. The sensitivity results show the high importance of ionic diffusion parameters and of exposure conditions, while the calculated initial mineral phases in the hydrated paste have lower importance.
  • Publication
    Accès libre
    Statistical analysis of concrete transport properties
    (E. & F. N. Spon, 2013-03-26) Grégoire, Étienne; Chouinard, Luc; Conciatori, David; Samson, Éric; Marchand, Jacques
    Results of a statistical analysis of transport properties measurements carried out on a number of concrete mixtures are presented. Migration and drying experiments were performed to evaluate the ionic diffusion coefficients and permeability of concrete mixtures. Seven concrete mixtures were tested. The mixtures were either batched under laboratory conditions or sampled from construction sites. For each mixture, approximately eighty concrete samples from a single batch were tested. Ionic diffusion coefficients were calculated by analyzing the evolution of the electrical current passing through concrete samples during the migration tests. Calculations took into account the volume of permeable pores of the materials and the pore solution chemistry. Permeability was calculated from mass loss measured during drying tests. The study indicates that the coefficient of variation of ionic diffusion coefficients is 11.1 % on average, with a maximum of 23.5 %, and that the coefficient of variation of permeability is 20.6 % on average, with a maximum of 37.3 %.