As argamassas de revestimento são amplamente utilizadas na construção civil e, suas propriedades no estado endurecido são fortemente influenciadas pelas propriedades no estado fresco, as quais dependem de fatores como: materiais empregados; forma de aplicação; e interação entre substrato e argamassa. Os ensaios utilizados para caracterização reológica das argamassas não contemplam as alterações que ocorrem devido o contato com o substrato, gerando discordâncias nas teorias sobre os fenômenos pelo qual ocorre a resistência de aderência. Sendo assim, o presente trabalho visa identificar as alterações do comportamento reológico de suspensões cimentícias aplicadas em substratos porosos por meio do ajuste do método do squeeze-flow. Para tanto, foram utilizadas duas configurações do squeeze-flow, com e sem confinamento do fluxo radial; três tipos de base, sendo uma metálica e duas porosas; e, pastas com diferentes materiais, a saber: cimento; cal e filler calcário. A escolha da pasta ao invés da argamassa foi basicamente por duas razões: primeiro, porque a pasta é a parcela da argamassa mais suscetível aos efeitos de sucção capilar do substrato; e segundo, para simplificar o cenário de análise, eliminando a variável areia. Ambas as configurações apresentaram-se viáveis na identificação da alteração do comportamento reológico da pasta, devido aos fatores como: tipo de substrato; o tempo de contato entre pasta e substrato; perda de água da pasta; e energia de mistura. Além disso, observou-se que os procedimentos adotados, assim como o auxílio de outros ensaios, podem colaborar em estudos da influência de fatores como: temperatura; rugosidade; ângulo de contato; distribuição granulométrica de pastas e argamassas; e, principalmente, compreender os fenômenos que ocorre no período denominado como tempo de puxamento, ao passo que este influencia diretamente na resistência de aderência. / Mortar renderings are used in most of the constructions and their properties in the hardened state are strongly influenced by the properties in the fresh state, which depend on factors such as materials used; application form; and interaction between substrate and mortar. The determination of rheological parameters of fresh mortars doesn\'t include the changes that occur due to contact with the substrate. It generates disagreements in the theories about the phenomena of formation of the bond strength. Therefore, this study aims to identify changes in the rheological behavior of cementitious paste applied to porous substrates by adjusting the squeeze flow method. For this, two configurations of squeeze flow were used, with and without confinement of the radial flow; three substrate types; and pastes with different materials, namely cement, lime and sand. The choice of paste instead of mortar was basically for two reasons: first, because the paste is the portion of mortar more susceptible to the effects of capillary suction of substrate; and second, to simplify scenario analysis, eliminating the variable sand. Both configurations were viable in the identification of the alteration of rheological behavior of paste, due to factors such as substrate type; the contact time between paste and substrate; loss of water from paste; and mixing energy. In addition, it was observed that the procedures adopted as well as the aid of the other tests can collaborate on studies of the influence of factors such as temperature, roughness, contact angle, particle size distribution of pastes and mortars; and above all to understand the phenomena that occurs in the initial periods of contact paste/substrate and consequently in the bond strength.

Pour ajuster la rhéologie des matériaux cimentaires et modifier leurs principales propriétés d'écoulement, l'utilisation des polymères organiques est nécessaire. L'objectif de cette thèse est de définir un cadre général physique permettant de caractériser qualitativement les conséquences de l'introduction d'un ou plusieurs polymères dans une pâte de ciment. De façon à s'affranchir des spécificités chimiques de chaque molécule, nous prenons le parti d'adopter une approche physique générale dans laquelle un polymère est défini par sa localisation (en solution ou à la surface d'un grain) et par sa taille caractéristique (en solution ou à la surface d'un grain). Nous sélectionnons des polymères couvrant la gamme de molécules disponibles lors de la formulation d'un matériau cimentaire : super-plastifiants, agents de viscosité, retardateurs de prise, floculants. Dans un premier temps, nous étudions le comportement des polymères dans le fluide interstitiel d'une pâte de ciment. Nous mesurons leurs rayons hydrodynamiques en solution et leur influence sur la viscosité du fluide interstitiel d'une pâte de ciment. Nous montrons qu'au premier ordre, la conformation, en régime dilué, de la majorité des polymères étudiés ici et tirés de la littérature, peut être décrite par la même courbe maitresse en fonction de la masse molaire. Nous identifions la fraction volumique des polymères en solution comme le paramètre principal qui est à même de capturer la physique dominante et commune à la majorité des polymères étudiés ici et régissant leur comportement macroscopique en solution. Nous étudions ensuite le comportement des polymères dans une pâte de ciment. Nous mesurons leur adsorption à la surface des particules de ciment et nous analysons les résultats obtenus dans deux régimes asymptotiques de la littérature: le régime d'adsorption à faible taux de couverture de surface et le régime d'adsorption à la saturation qui nous donnent respectivement des informations sur l'affinité intrinsèque du trio polymère/surface/solvant et sur la conformation des polymères adsorbés à la saturation. Nous discutons alors les valeurs d'affinité et d'adsorption à la saturation mesurées à la lueur des paramètres et des structures moléculaires de nos polymères. Dans une troisième partie, nous rappelons les origines physiques microscopiques du comportement rhéologique d'une pâte de ciment. Nous identifions, dans le cas où les polymères n'introduisent pas de nouvelles forces dans le système deux paramètres principaux, la distance inter-particulaire et la viscosité du fluide interstitiel, qui peuvent être ajustés par l'ajout de polymères et entrainer des changements majeurs dans la rhéologie d'une pâte de ciment standard. Dans une dernière partie, nous étudions la compétition d'adsorption entre polymères à la surface des particules de ciment. Nous proposons tout d'abord un protocole expérimental basé sur des mesures de diffraction dynamique de la lumière nous permettant de distinguer les adsorptions respectives de deux polymères sur une même surface. Nous illustrons ensuite la compétition d'adsorption et l'utilisation potentielle qui peut être faite de cette technique en étudiant successivement les compétitions d'adsorption entre un super-plastifiant et trois autres espèces adsorbantes : des ions sulfates, un retardateur de prise et un agent de viscosité. Nous montrons que, selon le taux de couverture de surface, cette compétition peut être plus au moins marquée et ses conséquences rhéologiques plus au moins drastiques. L'approche physique proposée ici consistant à ignorer autant que possible les spécificités chimiques des macromolécules étudiées atteint, à plusieurs occasions, ses limites. Lorsque c'est le cas, nous regroupons à la fin des parties concernées les discussions et analyses des situations où l'introduction d'un polymère dévie de la réponse générique au premier ordre obtenue pour l‘ensemble des autres macromolécules étudiées / To fulfil the rheological requirements of cementitious materials, mix designer engineers use various polymers. Theses admixtures either stay in the suspending fluid modifying its viscosity or adsorb at the surface of cement particles modifying their surface properties and their interactions. In this work, we propose a general physical frame allowing for the description of the consequences of the addition of one or various polymers on the rheology of cement paste. We identify two main parameters affecting the rheology of cement paste, which can be modified by chemical admixtures. These parameters are the inter-particle distance and the viscosity of the suspending fluid. Our solution viscosity and hydrodynamic radii measurements in synthetic cement pore solution suggest that the volume fraction of polymers is the main parameter enhancing the viscosity of the suspending fluid. By means of rheological and adsorption measurements, we study the effects of polymers on the inter-particle distance and the rheological behavior of the suspension. Finally, we study the competitive adsorption between polymers at the surface of cement particles. We propose a technique based on dynamic light scattering measurements allowing for the measurement of the respective adsorption of two polymers at the surface of cement particles. We then study the competitive adsorption between a super-plasticizer and sulfate ions, retarder or viscosity enhancing admixtures

Dès les premières utilisations des matériaux cimentaires, l'ajout de fibres a permis de renforcer ces matrices fragiles. Ces fibres, comme pour tout autre type d'inclusions, modifient les propriétés rhéologiques du matériau à l'état frais. Dans un premier temps, nous étudions spécifiquement l'influence de l'ajout des fibres sur le seuil d'écoulement de matériaux cimentaires. Nous considérons des écoulements suffisamment brefs pour que l'orientation des fibres soit négligeable. Nous montrons que, comme dans le cas d'inclusions sphériques, il existe une fraction volumique critique de fibres pour laquelle un réseau percolé de contacts directs entre inclusions se forme. Nous déduisons de ce constat une méthode permettant de prédire la quantité de fibres pour laquelle une augmentation de plusieurs ordres de grandeurs du seuil du matériau a lieu. Nous dérivons de cette étude des critères de formulation utilisables dans la pratique industrielle. Nous étendons dans un deuxième temps notre étude aux systèmes anisotropes de façon à prédire l'évolution de l'orientation des fibres lors de coulages industriels standards. Pour cela nous construisons et comparons des outils expérimentaux, analytiques ou numériques permettant respectivement de mesurer et de prédire l'orientation des fibres en fonction des caractéristiques des fibres, du comportement rhéologique du mélange et du procédé de mise en œuvre. Nous montrons que la majorité des écoulements industriels peut se réduire à des écoulements simples pour lesquels le processus d'orientation est décrit en première approximation par les travaux de Jeffery. Des zones mortes dans lesquelles la contrainte est inférieure au seuil du matériau conservent leur isotropie initiale. Nous montrons qu'à l'échelle d'un coulage industriel, l'orientation des fibres peut être considérée comme instantanée. Les méthodes étudiées s'avèrent capables de prédire l'orientation induite par les écoule ments expérimentaux / Fibers have always been added to cementitious materials in order to reinforce the brittle nature of the matrix. As for any other type of inclusions, fiber addition modifies the rheological behavior of the material in the fresh state. In a first part, we focus on the influence of fiber addition on the yield stress of cementitious materials. We only consider flows which are too short or with no steady streamlines for orientation to affect the behavior of the material. We show that, as for spherical inclusions, a critical fiber volume fraction leads to the formation of a percolation network between all the inclusions. Predictions of this critical volume fraction can be derived from experimental measurements, leading to a sudden increase of several orders of magnitude in yield stress. Industrial mix design criteria are finally proposed. This work is extended in a second part to anisotropic systems. We then focus on the prediction of fiber orientation during standard industrial castings. Tools are built and compared from experimental, analytical and numerical approaches in order to measure and predict fiber orientation as a function of fiber characteristics, suspension rheological behavior and casting process. It is shown that most industrial flows can be considered as simple flows during which fiber orientation process is, as a first approximation, described by the Jeffery theory. In plug flow zones, where stress is lower than the material yield stress, the initial isotropy is conserved. We show that, at the time scale of the casting process, fiber orientation can be considered as instantaneous. It is finally concluded that analytical and numerical methods used in this work enable to predict orientation induced by the flows experimentally validated

Le phénomène de carbonatation des matériaux cimentaires est l'une des causes majeures de la corrosion des armatures de structures en béton armé. Ce phénomène est étudié depuis de nombreuses années sur les ciments Portland ordinaires CEM I, et les mécanismes sont relativement bien identifiés. Néanmoins, on remarque que si l'on substitue une partie du ciment par des ajouts tels que des cendres volantes, la réaction pouzzolanique ou les réactions d'hydratation qui s'en suivront amèneront à un contenu molaire plus faible en CHet aboutiront à la création d'une plus grande quantité d'hydrates de type C-S-H. Le pouvoir tampon qu'exerce la portlandite sur le pH de la solution interstitielle sera affaibli et le matériau cimentaire sera potentiellement plus sensible à la présence de CO2 au travers d'une carbonatation des C-S-H qui sera plus marquée. D'un point de vue physique, les évolutions microstructurales induites par un niveau élevé de carbonatation des C-S-H deviennent complexes et peuvent accélérer la diffusion du CO2. Cette thèse a ainsi pour but de caractériser le comportement vis-à-vis de la carbonatation des ciments contenant de forts dosages en cendres volantes et de développer une modélisation des systèmes cimentaires correspondants. Des pâtes de ciment et mortiers ont été formulés avec des rapports E/C variables et différents taux volumiques de substitution en cendre volante. Après une longue cure endogène, des essais de carbonatation accélérée ont été réalisés (10% de CO2, 25°C et 63% HR). À diverses échéances, des essais destructifs (analyse thermique, porosimétrie au mercure et projection de phénolphtaléine) et non-destructifs (gammadensimétrie) ont permis de quantifier le dioxyde de carbone fixé dans chaque type d'hydrate (CH et C-S-H), les changements de microstructure induits (porosité, distribution poreuse), ainsi que l'eau de structure libérée par carbonatation. On a ainsi pu relier les changements de microstructure et la libération d'eau avec les niveaux de carbonatation de la portlandite et des C-S-H.Dans un second temps, la plateforme de modélisation, Bil (sous licence GPL), développée à l'Ifsttar a été utilisée comme support pour le développement d'un modèle aux volumes finis. Il permet de décrire simultanément des réactions chimiques couplées à un transport de matière. Les lois de comportement chimiques - microstructurales (évolution du volume molaire des C-S-H en fonction de leur état de décalcification) et hydriques (eau relarguée par la carbonatation) mises en évidence par la campagne expérimentale ont pu être ainsi introduites dans le modèle. La cinétique de dissolution de la portlandite est paramétrée par une réduction d'accessibilité des amas de cristaux de CH qui, au cours du temps, se recouvrent d'une gangue de calcite de moins en moins perméable. La contribution des C-S-H est prise en compte. Une approche thermodynamique originale permet de décrire leur état de décalcification à l'équilibre au cours de la carbonatation. Au final, de nombreuses espèces chimiques, ainsi que leur spéciation, sont introduites dans le modèle, notamment les alcalins qui ont un effet marqué sur le pH / Reaction of gaseous atmospheric CO2 with calcium-bearing phases in concrete infrastructure components is known to cause a lowering of alkalinity, leading to depassivation and corrosion of rebars. Carbonation mechanism is quite well understood from a physico-chemical point of view, especially in the case of materials made of OPC. Nonetheless the impact of supplementary cementitious materials (SCM), such as fly-ash, on carbonation is still an active research field. The pozzolanic reaction between CH and fly ash implies a lower portlandite content and a higher C-S-H content. Whilst CH is buffering the pH, its lower content in these materials may lead to a lower resistance to carbonation and to a higher contribution of C-S-H in terms of microstructural changes. Thus, this PhD thesis aims at understanding the effect of cement substitution by high contents of fly ash and develop a numerical model describing the carbonation of these cementitious materials. Accelerated carbonation tests (10% CO2, 25°C and 63% RH) were performed on various cement pastes containing fly ash (0%, 30% and 60% of volumic substitution and water-to-cement ratio before substitution of 0.45 and 0.6). Carbonation profiles were assessed by destructive and non-destructive methods such as thermogravimetric analysis and mercury intrusion porosimetry (destructive), as well as gamma-ray attenuation (non-destructive). Carbonation penetration was studied at different ages of CO2 exposure. By correlating microstructure changes with the degree of carbonation of each hydration product related to the formation of calcium carbonate, we are able to propose analytical relationships linking the decrease in porosity and the amount of released water to the carbonation level of CH and C-S-H.The modeling platform Bil (GPL) developed at Ifsttar was used to develop a reactive transport modeling of atmospheric carbonation, using a finite volume method. We introduced in the model the constitutive equations we highlighted using the experimental data. Microstructure evolution was quantified, taking into account the effect of the progressive decalcification of C-S-H linked to their molar volume, as well as the quantity of water released by carbonation. Combined with a kinetic formulation of CH dissolution, C-S-H decalcification was described by an original thermodynamic approach. In the end, many chemical species were introduced in the model, such as alkalis which strongly affect pH

Ce travail s'inscrit dans le contexte des recherches menées pour la modélisation des composites aléatoires, permettant de déterminer leurs propriétés mécaniques effectives (élasticité et résistance). Parmi les modèles micromécaniques, numériques ou analytiques, développés dans ce but, on retrouve certains qui prennent en compte les effets d'interfaces se produisant aux frontières des inclusions des composites. Ces interfaces ont, selon plusieurs auteurs, une grande influence sur les propriétés élastiques et de rupture. Les modèles les considérant à ce jour sont néanmoins limités aux cas d'inclusions sphériques ou cylindriques. Dans cette thèse, nous proposons plusieurs approches et modèles micromécaniques (ou multi-échelles) qui permettent de déterminer les propriétés élastiques et poroélastiques ainsi que les modes de ruptures de matériaux composites granulaires présentant divers effets d'interfaces. Les morphologies inclusionnaires étudiées ne se limitent pas à la forme sphérique mais s'étendent également aux inclusions ellipsoïdales ce qui nous a amené à examiner une rupture inter-granulaire anisotrope. Les modèles de rupture développés dans ce travail ont été appliqués aux gels de C-S-H (hydrates de la pâte de ciment) ce qui a permis d'améliorer les modèles de rupture consacrés aux pâtes durcies. Les prédictions de ces modèles ont pu être confrontées à des données expérimentales de résistance à la compression simple des pâtes / Modelling composite media in view of determining its effective mechanical behaviour has been the topic of a large number of research papers. Some analytical and numerical models that can be found in the scientific literature on this topic take into account the interface effects that can arise at inclusions' boundaries. These interfaces have a major influence on the mechanical properties of composites according to some researchers. However, the models considering them are limited to spherical and cylindrical inclusions. In this work, several multi-scale approaches and models are developed to consider interface effects in the determination of the effective elastic and poroelastic properties and the failure mechanisms of granular composites. These models are performed on both spherical and ellipsoidal shapes of inclusions. The latter has led us to investigate an anisotropic inter-granular failure in granular media. The failure models developed in this work are applied to the microstructure of C-S-H gels (a cement paste hydrate) in order to improve the existing models on cement paste failure. The predictions of these improved models are compared to experimental data on the compressive strength of cement pastes

Advances in multiscale material modeling of structural concrete have created an upsurge of interest in the accurate evaluation of mechanical properties and volume fractions of its nano constituents. The task is accomplished by analyzing the response of a material to indentation, obtained as an outcome of a nanoindentation experiment, using a procedure called the Oliver and Pharr (OP) method. Despite its widespread use, the accuracy of this method is often questioned when it is applied to the data from heterogeneous materials or from the materials that show pile-up and sink-in during indentation, which necessitates the development of an alternative method. In this study, a model is developed within the framework defined by contact mechanics to compute the nanomechanical properties of a material from its indentation response. Unlike the OP method, indentation energies are employed in the form of dimensionless constants to evaluate model parameters. Analysis of the load-displacement data pertaining to a wide range of materials revealed that the energy constants may be used to determine the indenter tip bluntness, hardness and initial unloading stiffness of the material. The proposed model has two main advantages: (1) it does not require the computation of the contact area, a source of error in the existing method; and (2) it incorporates the effect of peak indentation load, dwelling period and indenter tip bluntness on the measured mechanical properties explicitly. Indentation tests are also carried out on samples from cement paste to validate the energy based model developed herein by determining the elastic modulus and hardness of different phases of the paste. As a consequence, it has been found that the model computes the mechanical properties in close agreement with that obtained by the OP method; a discrepancy, though insignificant, is observed more in the case of C-S-H than in the anhydrous phase. Nevertheless, the proposed method is computationally efficient, and thus it is highly suitable when the grid indentation technique is required to be performed. In addition, several empirical relations are developed that are found to be crucial in understanding the nanomechanical behavior of cementitious materials.

<div><div><div><p>The exceptional long-term performance of concrete is a primary reason that this material represents a significant portion of the construction industry. However, a portion of this construction material is prone to premature deterioration for multi-physical durability issues such as internal frost damage, restrained shrinkage damage, and aggregate susceptibility to fracture. Since each durability issue is associated with a unique damage mechanism, this study aims at investigating the underlying physical mechanisms individually by characterizing the mechanical and thermal properties development and indicating how each unique damage mechanism may compromise the properties development over the design life of the material.</p><p>The first contribution of this work is on the characterization of thermal behavior of porous media (e.g., cement-based material) with a complex solid-fluid coupling subject to thermal cycling. By combining Young-Kelvin-Laplace equation with a computational heat transfer approach, we can calculate the contributions of (i) pore pressure development associated with solidification and melting of pore fluid, (ii) pore size distribution, and (iii) equilibrium phase diagram of multiple phase change materials, to the thermal response of porous mortar and concrete during freezing/thawing cycles. Our first finding indicates that the impact of pore size (and curvature) on freezing is relatively insignificant, while the effect of pore size is much more significant during melting. The fluid inside pores smaller than 5 nm (i.e., gel pores) has a relatively small contribution in the macroscopic freeze-thaw behavior of mortar specimens within the temperature range used in this study (i.e., +24 °C to -35 °C). Our second finding shows that porous cementitious composites containing lightweight aggregates (LWAs) impregnated with an organic phase change material (PCM) as thermal energy storage (TES) agents have the significant capability of improving the freeze-thaw performance. We also find that the phase transitions associated with the freezing/melting of PCM occur gradually over a narrow temperature range (rather than an instantaneous event). The pore size effect of LWA on freezing and melting behavior of PCM is found to be relatively small. Through validation of simulation results with lab-scale experimental data, we then employ the model to investigate the effectiveness of PCMs with various transition temperatures on reducing the impact of freeze-thaw cycling within concrete pavements located in different regions of United States.</p><div><div><div><p>The second contribution of this work is on quantification of mechanical properties development of cementitious composites across multiple length scales, and two damage mechanisms associated with aggregate fracture and restrained shrinkage cracking that lead to compromising the long-term durability of the material. The former issue is addressed by combining finite element method-based numerical tools, computational homogenization techniques, and analytical methods, where we observe a competing fracture mechanism for early- age cracking at two length scales of mortar (meso-level) and concrete (macro-level). When the tensile strength of the cement paste is lower than the tensile strength of the aggregate phase, the crack propagates across the paste. When the tensile strength of the cement paste exceeds that of the aggregate, the cracks begin to deflect and propagate through the aggregates. As such, a critical degree of hydration (associated with a particular time) exists below which the cement paste phase is weaker than the aggregate phase at the onset of hydration. This has implications on the inference of kinetic based parameters from mechanical testing (e.g., activation energy). Next, we focus on digital fabrication of a cement paste structure with controlled architecture to allow for mitigating the intrinsic damage induced by inherent shrinkage behavior followed by extrinsic damage exerted by external loading. Our findings show that the interfaces between the printed filaments tend to behave as the first layer of protection by enabling the structure to accommodate the damage by deflecting the microcrack propagation into the stable configuration of interfaces fabricated between the filaments of first and second layers. This fracture behavior promotes the damage localization within the first layer (i.e., sacrificial layer), without sacrificing the overall strength of specimen by inhibiting the microcrack advancement into the neighboring layers, promoting a novel damage localization mechanism. This study is undertaken to characterize the shrinkage-induced internal damage in 7-day 3D-printed and cast specimens qualitatively using X-ray microtomography (μCT) technique in conjunction with multiple mechanical testing, and finite element numerical modeling. As the final step, the second layer of protection is introduced by offering an enhanced damage resistance property through employing bioinspired Bouligand architectures, promoting a damage delocalization mechanism throughout the specimen. This novel integration of damage localization-delocalization mechanisms allows the material to enhance its flaw tolerant properties and long-term durability characteristics, where the reduction in the modulus of rupture (MOR) of hardened cement paste (hcp) elements with restrained shrinkage racking has been significantly improved by ~ 25% when compared to their conventionally cast hcp counterparts.</p></div></div></div></div></div></div>

Unreinforced masonry (URM) walls are often used as load-bearing or infill walls in buildings in many countries. Such walls are also commonly found in existing and heritage buildings in Canada. URM walls are strong structural elements when subjected to axial loading, but are very vulnerable under out-of-plane loads. This type of loading may come from different sources , including seismic or blast events. When subjected to blast, wall elements experience large pressures on one of their faces due to the high pressure produced in the air when an explosion takes place. This wave of compressed air travels in a very short time and hits the wall causing immense stresses, which result in large shear and bending demands that may lead to wall failure, and the projection of debris at high velocities that can injure building occupants. This failure process is highly brittle due to the very low out-of-plane strength that characterize such walls. In the past years, many investigations have been carried out to enhance the structural behaviour of unreinforced masonry walls under out-of-plane loading. Different strengthening methods have been studied, which include the use of polyurea coatings, the application of advanced fiber-reinforced polymer (FRP) composites or the use of concrete overlays in combination with high performance reinforcement. Fabric-reinforced cementitious matrix (FRCM) is a new composite material that overcomes some of the drawbacks of FRP. This composite material consists of applying coatings which consist of one or more layers of cement-based mortar reinforced with a corresponding open mesh of dry fibers (fabric). This material has been studied as a strengthening technique to improve in-plane and out-of-plane capacity of existing URM walls as well as other structural elements, mostly under seismic actions. This thesis presents an experimental and analytical study which investigates the effectiveness of using FRCM composites to improve the out-of-plane resistance of URM walls when subjected to blast loading. As part of the experimental program, three large-scale URM masonry walls were constructed and strengthened with 1,2 and 3 layers of FRCM using unidirectional carbon fabrics. In all cases the specimens were built as load-bearing concrete masonry (CMU) walls. To increase shear resistance, two of the walls were also grouted with a flowable self-compacting concrete (SCC) mortar. Blast tests were conducted using the University of Ottawa Shock Tube and the results are compared with control walls tested in previous research at the University of Ottawa. The experimental results show that the FRCM retrofit significantly improved the blast performance of the URM load-bearing walls, allowing for increased blast capacity and improved control of displacements. The performance of the retrofit was found to be dependent on the number of retrofit layers. As part of the analytical research, Single Degree of Freedom (SDOF) analysis was carried out to predict the blast behaviour of the strengthened walls. This was done by computing wall flexural strength using plane sectional analysis and developing idealized resistance curves for use in the SDOF analysis. In general, the analysis procedure is found to produce reasonably accurate results for both the resistance functions and wall mid-height displacements under blast loading.

Maintenance and rehabilitation of existing masonry and reinforced concrete structures are of great importance in the field of civil engineering. Due to deterioration and severe environment, numerous structures fail to meet functional or safety requirements, and as a result, they should be strengthened. Several methods have been utilized to repair the structures, including steel plate bonding, cable post-tensioning, and section enlargement. However, these methods bring disadvantages, such as significant added dead load and high labour cost. Therefore, externally bonding with composite materials has attracted considerable attention recently. Externally bonded fibre-reinforced polymer (FRP) sheets have been widely used to strengthen reinforced concrete and masonry structures. FRP has been a common method to provide a higher service life for structures for several decades. However, strengthening structural members with FRP introduces certain drawbacks, such as their poor performance in fire scenarios caused by the rapid softening of the polymer-based resin. An alternative strengthening system known as a fabric-reinforced cementitious matrix (FRCM) has been developed to address this issue by replacing resin-based material with an inorganic cementitious-based matrix. Nonetheless, the performance of FRCM at high temperatures has not been investigated sufficiently so far. Hence, this research focused on the mechanical behaviour of FRCM at high temperatures. This experimental research investigates the tensile performance of carbon FRCM at high temperatures. First, the temperature distribution within the specimens during heating was studied using nine specimens with one, two, or three layers to reveal the required time for the inner fabric to reach a steady temperature. Then, the tension and stiffness degradation of FRCM coupons were studied at different temperatures. A total of 84 FRCM coupons were fabricated and tested in tension; 60 of the tests were conducted at steady-state conditions in which temperature was held constant and load increased, and 24 specimens were carried out in transient-state tests, in which load was constant, and temperature grew. In order to provide a more comprehensive knowledge concerning the FRCM composite, some key variables were included in this research. These parameters are the number of layers (1, 2, 3) leading to different thicknesses (20, 30, 40 mm), the orientation of the fabric layer (unidirectional and bidirectional), target temperature (ambient, 100, 200, 300, 400°C), and heating condition (steady-state, transient state). These tests aimed to reveal the primary mechanical characteristics such as ultimate strength and cracked elastic modulus at different temperatures and compare them with control specimens tested at room temperature. With the increase in the number of fabric grids from one to two and three, the stress at failure decreased by about 11 and 18%, respectively. With regards to cracked elastic modulus two and three-layered specimens showed 18 and 20% reduction in value. It is also noteworthy to mention that overall load capacity of specimens rose with the increase in number of layers; however, due to the more significant increase in area, the stress was reduced. The same decreases in the cracked elastic modulus and ultimate strength were observed as the target temperature increased. Increasing the temperature to 400°C led to a decrease in ultimate strength and cracked elastic modulus of approximately 60 to 70%. Furthermore, the bidirectional specimens showed a better behaviour than unidirectional specimens in terms of ultimate strength; however, their cracked elastic moduli were almost the same. With regards to the transient-state tests, as the material became thicker, the failure temperature increased considerably. For instance, a 20-mm specimen failed at 467°C with a 20% sustained load, while a 30-mm specimen failed at 558°C. Another vital parameter studied in transient-state tests was the decrease in temperature with the increase in sustained load. An example of this is the 20-mm specimens which failed at 352 and 258°C, while they were preloaded to 40 and 60% of their capacities. The conclusions of this study suggest that FRCM materials do retain a non-negligible strength capacity at high temperatures. However, further investigations to reveal FRCM bond behaviour and retrofitted structural members at high temperatures are still required to provide comprehensive knowledge.

This research project has been undertaken to produce and characterize the behavior of High Strength Cementitious Mix (HSCM), which has considerably higher compressive strength compared to conventional concrete. Components of HSCM are cement, silica fume, sand, water, and high range water reducer. The material is tested for compressive strength and impact energy absorption capacity while the amount of above mentioned components are varied parametrically. The effect of these parameters are extensively studied and trends are reported. Finally, this research projects attempts to find correlations among compressive strength, compressive toughness, and impact toughness. Limitations of the experimental program are discussed and future direction for improvement and expansion of the research program is suggested.