An importantmatter in the field of building physics is the questioning of how wellbuildings sustain ageing, and how their overall efficiency evolves over their lifetime.Many causes for degradation are carried by moisture transfer through these porousmaterials. Indeed, infiltratedwatermay transport chemicals, altermechanical properties,and cause freeze thaw damage or mould development. It may also affect thermalproperties and energetic efficiency, as well as the health and comfort of the occupants.The understanding of how moisture transfer properties evolve during the lifespan ofbuildingmaterials is however far fromcomplete. The pore structure of amaterial itselfmay change over time, or be altered by cracks and defects caused bymechanical loadingand aggravated bymoisture-induced degradation. All sizes of fracturesmay have astrong impact on heat and moisture flow in the building envelope, and their influenceis to be accounted for in any long-termperformance assessment, not only of buildingand building components,but of any built structure in general. A considerable amountof work has already been performed in order to allow predicting the hygrothermal behaviourof buildings over longer periods of time. However, an accurate prediction of allranges of damage in a building component, from microscopic to macroscopic cracks,supposes an extensive knowledge of all damage-inducing, time-varying boundary conditionsof the problem during the simulation time. This also implies high computationalcosts, as well as important needs formaterial characterisation.As a complement to these predictive methods, a new approach was undertaken,combining experimental characterisation of crack patterns and numerical simulationsof coupled heat and moisture transfer. First, a preliminary study was conducted, consistingof measurements of the water vapour permeability of diffusely damaged constructionmaterials.This allowed identifying the experimental and numerical requirementsof the remainder of the work, which aimed at providing measurements of fracturenetwork geometries for their explicitmodelling in heat andmoisture transfer simulations.Digital image correlation and acoustic emission monitoring were then performedduring the degradation of cementitiousmaterials, in order to obtain quantitativedata on crack pattern geometries, and to assess the possibilities for damagemonitoringat the building scale. The optical technique, along with an appropriate imageprocessing procedure, was found suitable for providing precisemeasurements of fracturenetworks. Amethodwas also proposed for the interpretation of acoustic emissionrecordings in terms of damage quantification, localisation and identification.Then, a newmodel for coupled heat andmoisturemodelling in cracked porousmediawas developed, that allows including such measurements of fracture patterns intoa finite element mesh, and simulating flow accordingly. This model was validated onthe basis of experimentalmeasurements: digital image correlationwas performed duringthe fracturing of concrete samples, in which moisture uptake was then monitoredusing X-ray radiography. A good accordance was found between experimental and numericalresults in terms of 2-dimensional moisture concentration distributions. The validated code was then used for the simulation of test cases, in order to assess the hygrothermalperformance of damagedmulti-layered building components subjected toreal climatic conditions. The consequences of fractures on themoisture accumulationin walls, on the amplitude of sorption/desorption cycles and on the thermal performance,were observed.

Les transferts d’humidité dans les matériaux de construction ont une influenceimportante sur leur durabilité et sur les performances hygriques et thermiques desbâtiments. De nombreux mécanismes d’endommagement chimiques et physiquesde ces matériaux sont en effet dus à l’infiltration d’eau. En conséquence, leur structureporeuse peut évoluer au cours du temps, et des fissures microscopiques commemacroscopiques peuvent s’y développer. La description des matériaux à l’échelle microscopiqueest cependant une source d’erreur importante dans les codes de simulationactuels des transferts d’humidité et de chaleur, notamment en raison du faitque lesmilieux sont considérés comme homogènes, et que les effets du vieillissementdes matériaux sont négligés. Il importe donc de trouver un moyen d’inclure les effetsde l’endommagement dans les simulations de transferts d’humidité et de chaleurà l’échelle du bâtiment. Des méthodes existent pour la prédiction du comportementde milieux soumis à des sollicitations hygriques et mécaniques, mais supposent quel’ensemble des facteurs extérieurs influant sur l’endommagement soient connus toutau long des simulations.Une nouvelleméthodologie est proposée ici pour compléter ces approches prédictives,en combinant des mesures expérimentales d’endommagement avec la simulationde transferts couplés d’humidité et de chaleur. Une étude préliminaire a d’abordété menée, consistant à mesurer la perméabilité vapeur équivalente d’éprouvettes demortier multi-fissurées. Cette démarche a permis d’identifier les besoins expérimentauxet numériques de la suite du travail, visant à modéliser les écoulements dans unréseau discret de fissures sur la base de leur caractérisation. Une méthodologie expérimentalecombinant corrélation d’images numériques et émissions acoustiques aensuite été développée, permettant de disposer de cartographies d’endommagementet de proposer une démarche pour lamesure de réseaux de fissures dans lesmatériauxde construction en place. La méthode optique, associée à une procédure de traitementd’images, a permis de disposer de données précises de la géométrie de réseauxde fissures. De plus, une méthode a été proposée pour permettre l’interprétation desmesures d’émissions acoustiques en termes de quantification, localisation et identificationdes phénomènes d’endommagement.Un code de simulation a ensuite été écrit, permettant d’intégrer ces mesures defissuration dans la modélisation des écoulements couplés d’humidité et de chaleuren milieu poreux. Ce modèle a été validé sur la base de mesures expérimentales : lacorrélation d’images numériques a été appliquée durant la fracturation d’éprouvettesde béton, dans lesquelles l’infiltration d’eau a ensuite été suivie par radiographie auxrayons X. Les résultats numériques obtenus sont en bonne conformité avec lesmesuresexpérimentales en termes de prédiction de la concentration d’eau en deux dimensions.Enfin, laméthodologie a été appliquée à une série de cas test, dans le but demodéliserles performances hygrothermiques de parois multi-couches, incluant des matériauxendommagés, soumises à des conditions climatiques réelles. On a ainsi pu estimer les conséquences potentielles de l’endommagement sur l’accumulation d’eau dans desparois, sur l’amplitude des cycles de sorption et de séchage, ainsi que sur les transfertsthermiques. / An importantmatter in the field of building physics is the questioning of how wellbuildings sustain ageing, and how their overall efficiency evolves over their lifetime.Many causes for degradation are carried by moisture transfer through these porousmaterials. Indeed, infiltratedwatermay transport chemicals, altermechanical properties,and cause freeze thaw damage or mould development. It may also affect thermalproperties and energetic efficiency, as well as the health and comfort of the occupants.The understanding of how moisture transfer properties evolve during the lifespan ofbuildingmaterials is however far fromcomplete. The pore structure of amaterial itselfmay change over time, or be altered by cracks and defects caused bymechanical loadingand aggravated bymoisture-induced degradation. All sizes of fracturesmay have astrong impact on heat and moisture flow in the building envelope, and their influenceis to be accounted for in any long-termperformance assessment, not only of buildingand building components,but of any built structure in general. A considerable amountof work has already been performed in order to allow predicting the hygrothermal behaviourof buildings over longer periods of time. However, an accurate prediction of allranges of damage in a building component, from microscopic to macroscopic cracks,supposes an extensive knowledge of all damage-inducing, time-varying boundary conditionsof the problem during the simulation time. This also implies high computationalcosts, as well as important needs formaterial characterisation.As a complement to these predictive methods, a new approach was undertaken,combining experimental characterisation of crack patterns and numerical simulationsof coupled heat and moisture transfer. First, a preliminary study was conducted, consistingof measurements of the water vapour permeability of diffusely damaged constructionmaterials.This allowed identifying the experimental and numerical requirementsof the remainder of the work, which aimed at providing measurements of fracturenetwork geometries for their explicitmodelling in heat andmoisture transfer simulations.Digital image correlation and acoustic emission monitoring were then performedduring the degradation of cementitiousmaterials, in order to obtain quantitativedata on crack pattern geometries, and to assess the possibilities for damagemonitoringat the building scale. The optical technique, along with an appropriate imageprocessing procedure, was found suitable for providing precisemeasurements of fracturenetworks. Amethodwas also proposed for the interpretation of acoustic emissionrecordings in terms of damage quantification, localisation and identification.Then, a newmodel for coupled heat andmoisturemodelling in cracked porousmediawas developed, that allows including such measurements of fracture patterns intoa finite element mesh, and simulating flow accordingly. This model was validated onthe basis of experimentalmeasurements: digital image correlationwas performed duringthe fracturing of concrete samples, in which moisture uptake was then monitoredusing X-ray radiography. A good accordance was found between experimental and numericalresults in terms of 2-dimensional moisture concentration distributions. The validated code was then used for the simulation of test cases, in order to assess the hygrothermalperformance of damagedmulti-layered building components subjected toreal climatic conditions. The consequences of fractures on themoisture accumulationin walls, on the amplitude of sorption/desorption cycles and on the thermal performance,were observed.