Dissertations / Theses on the topic 'Mechanical and durability properties'

The focus of this research was to investigate the effect of thermal degradation upon the mechanical properties of natural rubber compounds and apply those effects to the life prediction of off axis 2-ply cord rubber laminates. The work examined both the quasi-static and dynamic mechanical properties of two natural rubber vulcanizates, which had been subjected to isothermal anaerobic aging. Thermal aging was performed on two different natural rubber vulcanizates. The thermal aging was conducted between the temperatures of 80 and 120°C for times ranging from 3 to 24 days. The effect of thermal degradation was measured from the changes in the chemical composition of the vulcanizates as functions of time at temperature. A master curve relationship between the changes in the chemical composition of the vulcanizates due to thermal degradation and their static and dynamic mechanical properties has been developed. This relationship allowed for the prediction of the vulcanizate mechanical properties after thermal aging. It was found that the mechanical properties correlated with the percentage of poly and monosulfidic crosslinks, where in general higher levels of polysulfidic crosslink gave rise to the highest mechanical properties. Crack propagation in an aged and unaged natural rubber vulcanizate was measured using a double cantilever beam, DCB. This type of testing arrangement exhibits a plane strain condition and resulted in crack growth rates two orders of magnitude faster than traditional plane stress testing geometries. To validate the DCB specimens, an investigation into the potential cavitation inside the rubber of the DCB specimens was performed. It was found that no cavitation occurred due to the high speed of the fracture. DCB samples were thermally aged to determine the effect of thermal aging upon the crack growth rate. It was found that crack growth rates increase with thermal aging. Life prediction of the aged 2-ply laminates was performed using a finite element analysis. In order to verify the finite element models used in the life prediction, the fatigue failure and crack growth characteristics of off axis 2-ply cord-rubber laminates were examined with a delamination analysis. This analysis allowed for the determination of the modulus of off axis 2-ply laminates in the presence of damage as well as the calculation of the crack growth rates of the laminate. The failure of unaged and thermally aged 2-ply laminates was evaluated and compared to the crack growth rates of thermally aged DCB specimens. The trend due to thermal aging between the two types of testing specimens was consistent. The finite element analysis was sectioned into two approaches: crack initiation and crack propagation. The former utilized a residual strength approach, while the latter applied a fracture mechanics approach. The predicted stress versus cycles, S-N, curves were not in complete agreement with the experimental data. The error between the predicted and the experimental is discussed and future work to correct that error is suggested. While there was not complete agreement between the predicted and the experimental data, this dissertation outlines a comprehensive approach to track the effects of thermal degradation and apply those effects to a real world application.
Ph. D.

The mechanical properties of unaged and aged constituent materials for solid oxide fuel cells were evaluated using microindentation, plate tensile, four-point bend, ball on ring and pressure on ring tests. The Vickers hardness of the anode, interconnect and electrolyte was determined before and after 1000 hours aging at 1000 oC in air. The fracture toughness KIC was found for the electrolyte materials. Finite element analysis (FEA) was validated and used to calculate the stress distribution and peak stress for the biaxial strength test. A Weibull analysis was carried out on the test/FEA-predicted peak stresses, and Weibull strength, modulus and material scale parameters were found for each test methodology. The methodologies were evaluated based on the results of the Weibull analysis and the pressure on ring test is preferred one for brittle thin film fracture strength testing. Half cell SOFCs with composite cathode (Pr0.7Sr0.3)MnO3±δ /8YSZ on the 8YSZ electrolyte were aged 1000 hours at 1000 oC in air with/without polarization and investigated using Electrochemical Impedance Spectroscopy (EIS), Scanning Electron Microscopy (SEM), Brunauer-Emmett-Teller (B.E.T.) method and X-ray Diffraction (XRD). The performance of the half cell SOFCs degraded after aging with/without polarization compared to the initial state, which was ascribed to the decrease of the electrolyte conductivity. The current load was shown to have impact on the performance by slowing down the decreasing rate of the polarization resistance of the SOFCs. After aging, the microstructural properties - pore size and pore volume changed, and growth of grains was found on the (Pr0.7Sr0.3)MnO3 phases, which may have contributed to the decrease of the activation polarization by decreasing the capacitance and increasing the number of active sites. After aging the high frequency EIS arcs/peaks shifted to a lower frequency range, and the low frequency arcs/peaks became unapparent compared to before aging. A 3-D multiphysics finite element model was used to simulate the performance of the half cell SOFC. The effective exchange current density and the effective ionic conductivity of the cathodes showed much influence on the performance of the SOFC. Predicted and observed performance was compared. Suggestions were given for the further experiments on the composite cathode.
Ph. D.

Wood pulp fibers are a unique reinforcing material as they are non-hazardous, renewable, and readily available at relatively low cost compared to other commercially available fibers. Today, pulp fiber-cement composites can be found in products such as extruded non-pressure pipes and non-structural building materials, mainly thin-sheet products. Although natural fibers have been used historically to reinforce various building materials, little scientific effort has been devoted to the examination of natural fibers to reinforce engineering materials until recently. The need for this type of fundamental research has been emphasized by widespread awareness of moisture-related failures of some engineered materials; these failures have led to the filing of national- and state-level class action lawsuits against several manufacturers. Thus, if pulp fiber-cement composites are to be used for exterior structural applications, the effects of cyclical wet/dry (rain/heat) exposure on performance must be known. Pulp fiber-cement composites have been tested in flexure to examine the progression of strength and toughness degradation. Based on scanning electron microscopy (SEM), environmental scanning electron microscopy (ESEM), energy dispersive spectroscopy (EDS), a three-part model describing the mechanisms of progressive degradation has been proposed: (1) initial fiber-cement/fiber interlayer debonding, (2) reprecipitation of crystalline and amorphous ettringite within the void space at the former fiber-cement interface, and (3) fiber embrittlement due to reprecipitation of calcium hydroxide filling the spaces within the fiber cell wall structure. Finally, as a means to mitigate kraft pulp fiber-cement composite degradation, the effects of partial portland cement replacement with various supplementary cementitious materials (SCMs) has been investigated for their effect on mitigating kraft pulp fiber-cement composite mechanical property degradation (i.e., strength and toughness losses) during wet/dry cycling. SCMs have been found to be effective in mitigating composite degradation through several processes, including a reduction in the calcium hydroxide content, stabilization of monosulfate by maintaining pore solution pH, and a decrease in ettringite reprecipitation accomplished by increased binding of aluminum in calcium aluminate phases and calcium in the calcium silicate hydrate (C-S-H) phase.

In 1995, the Swedish government recommended the discontinuation of amalgam as restorative in paediatric dentistry. Because the mercury content in amalgam constitutes an environmental hazard, its use has declined. The use of resin composites is increasing, but the polymerisation shrinkage of the material is still undesirably high, and the handling of uncured resin can cause contact dermatitis. A new restorative material has recently been developed in Sweden as an alternative to amalgam and resin composite: a calcium aluminate cement (CAC). CAC has been marketed as a ceramic direct restorative for posterior restorations (class I, II) and for class V restorations. This thesis evaluates mechanical properties and clinical durability of the calcium aluminate cement when used for class II restorations. Hardness, in vitro wear, flexural strength, flexural modulus, and surface roughness were evaluated. A scanning electron replica method was used for evaluation of the interfacial adaptation to tooth structures in vivo. The durability was studied in a 2-year intra-individually clinical follow-up of class II restorations. Major results and conclusions from the studies are as follows: • The CAC was a relatively hard material, harder than resin-modified glass ionomer cement but within the range of resin composites. The CAC wore less than resin-modified glass ionomer cement but more than resin composite. • Flexural strength of CAC was in the same range as that of zinc phosphate cement and far below that of both resin composite and resin-modified glass ionomer cement. Flexural modulus of CAC was higher than both resin composite and resin-modified glass ionomer cement. The low flexural strength of CAC precludes its use in stress-bearing areas. • Surface roughness of CAC could be decreased by several polishing techniques. • For CAC restorations, interfacial adaptation was higher to dentin but lower to enamel compared with resin composite restorations. Fractures were found perpendicular to the boarders of all CAC restorations and may indicate expansion of the material. • After 2 years of clinical service, the class II CAC restorations showed an unacceptably high failure rate. Material fractures and tooth fractures were the main reasons for failure.

Disposal and treatment of construction and demolition (C&D) wastes are often costly and hazardous to the environment. Their recycling could lead to a greener solution to the environmental conservation and pave the way towards sustainability. This study utilizes demolished concrete as coarse aggregate often termed as recycled coarse aggregate (RCA) for producing industry quality concrete. Large scale recycling can substantially reduce the consumption of natural aggregate and help preserve the environment. However, in near future, it can raise new challenges. The use of “repeated recycled coarse aggregate” in concrete production can be a viable solution to the growing problem regarding the C&D waste disposal. During the development of new generation product like recycled and repeated recycled coarse aggregate concrete, it is essential to investigate the fresh, hardened, and durability properties of concrete to promote and escalate its application in the construction industry. This research investigates the fresh, mechanical, and durability properties of 25 MPa recycled aggregate concrete (RAC) made with different RCA replacement levels. Durability performance of 25 MPa RAC was evaluated in terms of sulphate attack and cyclic wetting and drying along with chloride exposure. Chloride propagation was evaluated after 1, 4, 9, 16, 28, 90, and 120 cycles. This study reveals that the performance of RAC is decreasing with increasing RCA replacement levels but their overall performance is comparable to natural aggregate concrete (NAC). Three different generations of repeated recycled coarse aggregate concrete were produced using 100% RCA as a replacement of natural coarse aggregate. Similar mix design was used for producing 32 MPa concrete. Along with this, their durability performance was examined under three different exposure conditions namely, freeze-thaw, sulphate, and chloride exposure. It was found that the compressive strength of different generations of repeated recycled concrete was lower than the control concrete. However, all of the mixes exceeded the target strength at 120 days. The durability performance of the different generations of repeated recycled coarse aggregate concrete was negatively affected by using different generations of such aggregates but still these findings will add a new achievement towards sustainable world.

The review of municipal solid waste (MSW) management scheme has indicated that the amount of MSW sent to incineration plants will increase in the UK in coming years. Therefore, the amount of municipal solid waste incineration (MSWI) residues generated will increase significantly. MSWI residues are divided into MSWI fly ash (MSWI-FA) and MSWI bottom ash (MSWI-BA). MSWI-FA is classified as hazardous residue thereby requires special treatment before disposal. MSWI-BA is mostly disposed in landfill sites. MSWI-BA fraction with particle size diameter below approximately 2mm has low engineering properties and may have an adverse effect on the environment due to its high porosity, solubility and leachability of possible toxic compounds. This research programme has investigated new potential uses and leaching behaviour of mortar containing MSWI-BA with particle size diameters below 2.36mm. Fraction of MSWI-BA with particle size diameters (&phis;) below 2.36 mm (&phis; <2.36) was divided into different sub-fractions to evaluate their influence on compressive strength of concrete when used as partial replacement of cement or sand. MSWI-BA fraction with &phis; <212mum (fine fraction) and 212mum < &phis;2.36mm (coarse fraction) used as partial replacement of cement and sand respectively, showed higher compressive strength compared with the other fractions examined. In addition, replacing sand with the coarse fraction of MSWI-BA exhibited similar or higher strength than the reference mix. Examination of physical and chemical properties of the fine and coarse fractions of MSWI-BA unbound indicated that both fractions had potential to be used as replacement of cement or sand. However, the evaluation of their leaching behaviour suggested that they should be bound in cement-based systems to avoid leaching of potential toxic elements. Evaluation of physical, mechanical and sulfate resistance properties of mortars containing 15% of the fine fraction of MSWI-BA as a partial replacement of cement and 50% of the coarse fraction as partial replacement of sand indicated potential uses in concrete production. In addition, the leachability of mortar specimens containing 15% and 50% of MSWI-BA as partial replacement of cement and sand respectively was significantly reduced when compared to unbound MSWI-BA fractions.

Porous ceramics and porous ceramic composites are emerging functional materials that have found numerous industrial applications, especially in energy conversion processes. They are characterized by random microstructure and high porosity. Examples are ceramic candle filters used in coal-fired power plants, gas-fired infrared burners, anode and cathode materials of solid oxide fuel cells, etc. In this research, both experimental and theoretical work have been conducted to characterize and to model the mechanical behavior and durability of this novel class of functional material. Extensive experiments were performed on a hot gas candle filter material provided by the McDermott Technologies Inc (MTI). Models at micro-/meso-/macro- geometric scales were established to model the porous ceramic material and fiber reinforced porous ceramic material. The effective mechanical properties are of great technical interest in many applications. Based on the average field formalism, a computational micromechanics approach was developed to estimate the effective elastic properties of a highly porous material with random microstructure. A meso-level analytical model based on the energy principles was developed to estimate the global elastic properties of the MTI filament-wound ceramic composite tube. To deal with complex geometry, a finite element scheme was developed for porous material with strong fiber reinforcements. Some of the model-predicted elastic properties were compared with experimental values. The long-term performance of ceramic composite hot gas candle filter materials was discussed. Built upon the stress analysis models, a coupled damage mechanics and finite element approach was presented to assess the durability and to predict the service life of the porous ceramic composite candle filter material.
Ph. D.

Materials derived from chicken feathers could be used advantageously in composite building material applications. Such applications could potentially consume the five billion pounds of feathers produced annually as a by-product of the U.S. poultry industry. To aid the development of successful applications for chicken feather materials (CFM), the physical and mechanical properties of processed CFM have been characterized in this research. Results describing the moisture content, aspect ratio, apparent specific gravity, chemical durability, Youngs modulus, and tensile strength for processed CFM and specifically their fiber and quill components are presented herein. Processed chicken feather fiber and quill samples were found to have similar moisture contents in the range of 16 - 20%. The aspect ratio (i.e., length/diameter) of samples were found to be in the range of 30 - 50, and the fiber material was found to have a larger aspect ratio than the quill material. A comparison with values in the literature suggests that different processing regimes produce CFM with higher aspect ratios. Samples were found to have apparent specific gravities in the range of 0.7 - 1.2, with the fiber material having a higher apparent specific gravity than the quill material. A comparison with values in the literature suggests that apparent specific gravity results vary with fiber length and approach the value for keratin as fiber length decreases and internal voids become increasingly accessible. Chemical durability results showed that CFM rapidly degrade in highly alkaline (pH=12.4) environments and are, thus, likely incompatible with cement-based materials without special treatment. The Youngs modulus of processed chicken feather materials was found to be in the range of 3 - greater than 50 GPa and, thus, comparable to the Youngs moduli of other natural fibers. The tensile strength of oven-dried samples was found to be in the range of 10 - greater than 70 MPa. In agreement with results in the literature, the fiber material was found to have a greater tensile strength than the quill material. Finally, a simplified approach for comparing the effective Youngs moduli and effective tensile strengths of various processed CFM samples was introduced.

La prédiction de la durée de vie des polymères en milieu marin est devenue, ces dernières années, indispensable afin de limiter les coûts de maintenance des structures utilisées en mer. Le polychloroprène est un élastomère très employé en milieu marin en raison de ses propriétés intrinsèques proches de celles du caoutchouc naturel, avec une durabilité supérieure. Ce travail de thèse a pour objectif de caractériser, comprendre et prédire l'évolution des propriétés mécaniques (module et rupture) au cours du vieillissement et plus particulièrement de l'oxydation, l'un des mécanismes de dégradation majeurs pour ce type de matériaux. Cette prédiction est basée sur l'utilisation d'une description mécanistique de l'oxydation couplée à l'utilisation de relations structure/propriétés issues de la théorie caoutchoutique. Dans un premier temps, un modèle cinétique d'oxydation a été mis en place sur le polychloroprène cru et les constantes associées déterminées par méthode inverse. L'effet de la vulcanisation est, par la suite, intégré au modèle cinétique permettant ainsi une prédiction du module au cours de l'oxydation, ce type de dégradation conduisant à une forte augmentation du module dans le CR en raison de la présence de doubles liaisons dans le matériau. Afin de proposer une prédiction basée sur les propriétés à rupture, l'influence de l'oxydation sur l'énergie de propagation de fissure en mode I (GIC) a été étudiée en détail avec notamment une comparaison entre différents types d'élastomère. Cette étude a permis de mettre en évidence une chute importante de GIC en raison d'une inhibition de la cristallisation induite au cours de l'oxydation. La dernière partie de ce travail est dédiée à la diffusion de l'eau dans le polychloroprène et plus particulièrement les mécanismes de formation d'agrégat d'eau dans le matériau qui se traduit par une forte absorption et donc une perte de propriétés mécaniques à la rupture
The prediction of the lifetime of polymers in a marine environment is becoming increasingly important in order to limit maintenance costs for structures at sea. Polychloroprene is an elastomer which is widely used in marine structures due to its properties which are similar to natural rubber but with improved durability. The aim of the work described in this thesis is to characterize, understand and predict the evolution of mechanical properties (modulus and rupture) during aging, and in particular during oxidation, one of the main degradation mechanisms in this type of material. The prediction is based on the use of a mechanistic description of oxidation coupled with the use of theoretical structure/property relationships. First a kinetic model of oxidation has been set up for raw polychloroprene, and the associated rate constants have been found by an inverse method. The effect of vulcanization was then included in the model, enabling modulus to be predicted during oxidation. As a result of the presence of double bonds oxidation causes a significant increase in modulus of CR. Then, in order to predict fracture properties, the influence of oxidation on the mode I crack propagation energy (GIc) has been studied in detail, with a comparison between different types of elastomer. This study has revealed a strong drop in GIc due to inhibition of induced crystallization during oxidation. In the last part of the document the diffusion of water in polychloroprene has been examined, and the mechanisms of cluster formation have been described: These lead to large water absorption and a loss of mechanical properties

El texto completo de este trabajo no está disponible en el Repositorio Académico UPC por restricciones de la casa editorial donde ha sido publicado.
This study aimed to investigate the mechanical and durability properties of recycled aggre-gate concrete with a ternary binder system and optimized mix proportion. Two concretebatches were developed using a densified mix design approach (DMDA) to evaluate therequired mix proportions. Batch I have GGBS content varied at 0%, 10%, 20%, 30%, 40% and50% at constant w/b ratio of 0.45, while batch II concrete mix have varied water/binder ratios:0.3, 0.35, 0.4, 0.45 and 0.5 at constant GGBS replacement level of 30%. The fine aggregate(river sand) of the two batches was blended with fly ash at optimum loose packing density(FA + Sand) and superplasticizer (SP) was incorporated in the mix at a constant level of 1.4%.A control mix comprising of natural aggregate was also developed. The results obtainedshowcased the feasibility of producing structural concrete with recycled aggregates usingGGBS and fly ash. The mechanical and durability properties were best at 30% GGBS contentand 0.35 water/binder ratio. The DMDA for mix proportion adopted for RAC contributed sig-nificantly to improving its properties when compared to NAC, especially at the optimumobserved RAC mix with compressive strength of 52 MPa. Also, the mix demonstrated goodpermeability resistance in terms of chloride-ion ingress and capillary water absorption.

Radiata pine is a major plantation grown wood in the Southern hemisphere, but has inferior dimensional stability and low durability compared to other commercial species and the improvement of these features is the focus of this thesis. Specifically this thesis examines the dimensional stability, durability and mechanical properties of radiata pine after heat-treatment (160-210°C) in linseed oil. Changes in colour, micro-structure and chemistry with heat-treatment were studied. To optimise the treatment results, oil heat-treatment of wood was also carried out after thermo-mechanical compression of wood and the effect of the prior thermo-mechanical compression on stability, durability and mechanical properties were examined. The oil heat-treated wood turned uniformly darker in colour. The hydrophobicity (Water Repellence Efficiency-WRE up to 30%), dimensional stability (Ant-Swelling Efficiency-ASE up to 60%) and fungal resistance (up to 36%) were improved with the extent of the changes mainly depending on treatment temperature. However, the mechanical properties of oil heat-treated wood were reduced compared to the untreated control group. Accelerated UV weathering tests have shown that the oil heat-treated wood retained its colour and dimensional stability better than the untreated wood (the control group). The cell wall of treated wood was intact and no distinct structural changes were observed even at the most severe treatment (210°C for 6 hrs).The treatment resulted in changes to the wood chemical constituents, mainly the degradation of hemicelluloses which is believed to be principal reason for alterations in wood properties. A study of the effect of prolong heating on the linseed oil showed an increase in viscosity with heating time which in turn reduced the oil uptake and water repellency of treated wood. However, no significant difference in the colour and dimensional stability of the treated wood was noticed with oil of different heating ages. Oil absorbed by the wood during heat treatment was removed by organic solvent extraction and its contribution to the weight percentage change and moisture related properties were evaluated. The oil uptake percentage, determined by organic solvent extraction, was greater than the weight percentage loss that was deduced to occur during the heat treatment phase, which was attributed to mass losses or thermal degradation of wood constituents. Moisture excluding efficiency decreased after removal of the oil from treated wood, which suggested that the hydrophobicity of treated wood is affected by oil absorbtion. The influence of the post-treatment cooling period on properties of treated wood was studied separately. Oil uptake increased substantially with the post-treatment cooling time which in turn affected the hydrophobicity of treated wood although this effect was less important to dimensional stability. The loss of mechanical properties due to heat-treatment was successfully countered by thermo-mechanical compression of wood prior to the oil heat-treatment. The wood was compressed to 39% of its original thickness without any visible surface checks and cracks. Spring back and compression set recovery in densified wood decreased after oil heat-treatment. This combination treatment also resulted in improved fungal resistance compared to untreated wood. From this research, it is concluded that oil heat-treatment of radiata pine wood can improve its dimensional stability and durability obviating the need to introduce any persistent toxic chemicals. Thermo-mechanical densification of wood prior to oil heat-treatment can countered the loss of mechanical properties due to heat-treatment. The heating oil can be re-used in subsequent treatments and oil uptake can be minimised by limiting the post-treatment cooling time without any significant effect on the dimensional stability of treated wood.

In this dissertation, novel approaches to PEMFC durability research are summarized. These efforts are significantly different from most other studies on durability in that rather than focusing on chemical degradation, more attention is given to the mechanical aspects of the PEMFC system. The tensile stress-strain behavior of Nafion® 117 (N117) and sulfonated poly(arylene ether sulfone) random copolymer (BPSH35) membranes is explored under ambient conditions, with respect to the effects of initial strain rate, counterion type, molecular weight and the presence of inorganic fillers. A three-dimensional "bundle-cluster" model is proposed to interpret the tensile observations, combining the concepts of elongated polymer aggregates, proton conduction channels as well as states of water. The rationale focuses on the polymer bundle rotation/interphase chain readjustment before yielding and polymer aggregates disentanglement/ reorientation after yielding. In addition, the influence of uniaxial loading on proton conductivity of N117 and BPSH35 membranes is investigated. When the membranes are stretched, their proton conductivities in the straining direction increase compared to the unstretched films, and then relax exponentially with time. The behavior is explained on the basis of the morphological variations of hydrophilic channels, accompanied by the rotation, orientation and disentanglement of the copolymer chains in the hydrophobic domains, as illustrated with the help of our bundle-cluster model. Finally, the long-term aging of hydrogen-air PEMFCs is examined with a cyclic current profile and under constant current conditions. The end-of-period diagnosis is performed for both MEAs at 100h aging intervals, including a series of cell polarization, impedance and electrochemical experiments. The results demonstrate that hydrogen crossover is the most significant result of degradation for the MEA under cyclic aging mode due to the formation of pinholes at approximately 500-600h, and mass transport limitations are the major degradation sources for constant current mode. A phenomenological mathematical model is set up to describe the PEMFC aging process under both cyclic and constant conditions.
Ph. D.

The objective of this study was to evaluate and gain a better understanding of the short-term impact performance and the long-term durability of electrically conductive adhesives for electronic interconnection applications. Three model conductive adhesives, designated as ECA1, ECA2 and ECA3, supplied by Emerson & Cuming, were investigated, in conjunction with printed circuit board (PCB) substrates with metallizations of Au/Ni/Cu and Cu, manufactured by Triad Circuit Inc. Effects of environmental aging on the durability of conductive adhesives and their joints were evaluated. All the samples for both mechanical tests and thermal tests were aged at 85%, 100%RH for periods of up to 50 days. Studies of bulk conductive adhesives suggested that both plasticization, which is reversible and further crosslinking and thermal degradation, which are irreversible, might have occurred upon exposure of ECAs to the hot/wet environment. The durability of electrically conductive adhesive joints was then investigated utilizing the double cantilever beam (DCB) test. It was observed that the conductive adhesive joint was significantly weakened following hydrothermal aging, and there was a transition from cohesive failure to interfacial failure as aging continued. A comparative study of the durability of different conductive adhesive and substrate metallization combinations suggested that the resistance of the adhesive joints to moisture attack is related to the adhesive properties, as well as the substrate metallizations. It was noted that the gold/adhesive interface had better resistance to moisture attack than the copper/adhesive interface. A reasonable explanation of this phenomenon was given based upon the concept of surface free energy and interfacial free energy. XPS analysis was performed on the fractured surfaces of DCB samples. For adhesive joints with copper metallization, copper oxide was detected on the failed surfaces upon exposure of the conductive adhesive joints following aging. XPS analysis on the fractured surfaces of adhesive joints with Au metallization suggested that diffusion of Cu to the Au surface might have happened on the Au/Ni/Cu plated PCB substrates during aging. The impact performance of conductive adhesives was quantitatively determined using a falling wedge test. This unique impact resistance testing method could serve as a useful tool to screen conductive adhesives at the materials level for bonding purpose. Moreover, this test could also provide some useful information for conductive adhesive development. This study revealed that the viscoelastic energy, which is a result of the internal friction created by chain motions within the adhesive material, played an important role in the impact fracture behavior of the conductive adhesives. This study also demonstrated that the loss factor, evaluated at the impact environment conditions, is a good indicator of a conductive adhesive's ability to withstand impact loading.
Ph. D.

Typical rubber compounds used to manufacture industrial products such as tyres, hoses, conveyor belts, acoustics, shock pads, and engine mountings contain up to eight classes of chemical additives· including curing agents, accelerators, activators, processing aids, and antidegradants. The cure systems in these articles often consists of primary and secondary accelerators, primary and secondary activators, and elemental sulphur. Recent legislation impacting upon the working environment, safety and health has imposed a considerable burden on the manufacturers of rubber compounds to meet various obligations. The selection of raw materials and manufacturing processes that do not harm the environment is of great importance. A novel technique for preparing rubber formulations using crosslinking nanofillers such as silanised precipitated silica has been developed in this research. The silica surfaces were pre-treated with bis[3-triethoxysilylpropyl-] tetrasulphane coupling agent (TESPT).· TESPT is a sulphur containing bifunctional organosilane which chemically adheres silica to rubber and also prevents silica from interfering with the reaction mechanism of sulphur-cure systems. The tetrasulphane groups of the TESPT are rubber reactive and react in the presence of accelerator at elevated temperatures, i.e.140 -260°C, with or without elemental sulphur being present, to form crossIinks in rubbers containing chemically active double bonds for example styrene-butadiene rubber (SBR) and polybutadiene rubber (BR) .. SBR and BR rubber compounds containing 60 phr of TESPT pre-treated silica nanofiller were prepared. The silica particles were fully dispersed in the rubber, which was cured primarily by using sulphur in TESPT. The reaction between the tetrasulphane groups of TESPT and the rubbers was optimised by incorporating different accelerators and activators in the rubber. The mechanical properties of the rubber vulcanisates such as hardness, tear strength, tensile strength, elongation at break, stored' energy density at break, abrasion resistance, modulus and cyclic fatigue life were increased significantly when the treated silica filler was added. The need for the accelerator and activator was dependent on the composition of the rubber. Interestingly, the rubbers were fully cured without the use of elemental sulphur, secondary accelerator and secondary activator. As a result, a substantial reduction in the use of the curing chemicals was achieved without compromising the important properties of rubber compounds which are essential for maintaining long life and good performance of industrial rubber products in service. This approach has also helped to improve health and safety within the workplace and minimise harm to the enviromnent.Furthermore, a significant cost saving was achieved after reducing the number of curing chemicals in the rubber.

Une étude expérimentale a été menée afin de protéger des attaques biologiques des contreplaqués faits d'essences non durables (hêtre et peuplier), et ce, avec un faible impact environnemental. Des produits de protection à base de tannins et de bore, nouvellement développés afin de réduire le lessivage du bore, ont été sélectionnés pour ce but. Ce système a été utilisé pour protéger les contreplaqués selon deux approches : (1) au niveau de la colle pour remplacer les adhésives à base de formaldéhyde et coller les plis, (2) en traitement des plis avec des formulations plus diluées, les plis étant collés avec des adhésifs mélamine-urée-formaldéhyde. Les données expérimentales de cette thèse peuvent être classées en trois grands groupes : essais chimiques et thermomécaniques des colles tannin-bore, mesure des propriétés physiques et mécaniques, de la résistance biologique avant et après vieillissement des différents panneaux. Les essais chimiques sur les colles tannin/hexamine ont montré que l'addition de bore sous forme d'acide borique peut contribuer à plus de liaisons inter-flavonoids et à ouvrir les cycles pyranes ce qui accélère les réactions de polymérisation. Des analyses thermomécaniques sur les colles contenant des tannins de mimosa et de quebracho ont confirmé que l'addition d'acide borique (1) abaissait le temps et la température de prise, et (2) augmentait les valeurs du module d'élasticité de la colle. L'addition d'une quantité optimale d'acide borique dans la colle à base de tannin augmente les propriétés physiques et la résistance au cisaillement. Une charge excessive d'acide borique (10%) dans la colle est la cause de pertes de propriétés mécaniques et physiques. Bien qu'en faible quantité, l'introduction de l'acide borique dans la colle de tannin amène une protection efficace contre l'attaque fongique, même après un lessivage selon l'EN 1250-2. Les résultats des essais termites montrent que l'acide borique contenu dans la colle cause le plus faible taux de survie des insectes et de perte de masse, mais présentent un fort degré d'attaque selon une cotation visuelle. Aucune amélioration n'a été obtenue lors d'un essai de choix après lessivage. Les contreplaqués faits de plis traités par des solutions tannin-bore ont montré des résistances au cisaillement plus faibles, mais toujours dans les gammes requises pour des applications en atmosphère humide. Des résultats satisfaisants ont été obtenus par les réseaux polymères de tannins, même après une lessivage sévère, vis-à-vis de l'attaque fongique. Les contreplaqués faits de plis traités à l'acide borique seul ont présenté une sensibilité importante à l'attaque biologique après un lessivage. Les résultats des essais termites ont montré un faible taux de survie des insectes et de perte de masse, même après un lessivage sévère, pour les contreplaqués avec des plis traités par des systèmes tannin-bore. Les résultats d'un essai de choix a montré que les termites préféraient se nourrir des témoins quand l'alternative proposée était des échantillons traités avec des systèmes tannin-bore
An experimental investigation was conducted to protect plywood panels made of perishable wood species (beech and poplar) against biological attacks with low environmental impact. The newly developed tannin-boron preservative which was proposed to reduce the leaching of borates was selected for this purpose. This system was used to protect plywood with two approaches: (1) in the glue line to replace formaldehyde based adhesives and gluing wood veneers, (2) pretreatment of wood veneers with the diluted formulations and bonded with melamine-urea-formaldehyde resin The research data in this thesis were obtained from three main groups of experiments: chemicals and thermomechanical testing on the tannin-boron resin, measuring physical and mechanical properties, and different biological tests before and after leaching processes. The chemicals testing on the tannin/hexamine adhesive showed that the addition ofboron, in the form of boric acid, can contribute more inter-flavonoid linkages and the opening of pyran rings which leads to the acceleration of polymerization reactions. Thermomechanical analysis on the adhesives of mimosa and quebracheo tannins confirmed that the addition of boric acid (1) lowered time and temperature of hardening, (2) and increased modulus of elasticity values of the adhesive. The addition of optimal boric acid into the tannin adhesive upgraded physical properties and tensile shear strength. An excess loading of boric acid (10%) in the glue line caused imperfect physical and mechanical features. Despite the low uptake of boric acid but its addition into the tannin glue provided effective resistance against fungal attack even after mild leaching test according to the EN 1250-2. The results of termites test showed that increase in the boric acid content of the adhesive caused the lower survival rate and the weight loss but samples underwent the high level of attack. No improvement against termite attack was obtained after leaching by a choice feeding test. The plywoods made of pretreated veneers by tannin-boron solutions showed partially lower tensile shear strength but still in the range of standards requirements for the humid applications. The satisfactory results were obtained even after severe leaching test against fungal attack with a strong polymeric network of tannin. The control plywoods made of pretreated veneers with boric acid alone solutions presented significant sensitivity against biological attack after leaching test. The results of termite tests showed the lower survival rate and the weight loss even after severe leaching test for the plywoods made of pretreated veneers with tannin-boron systems. The results of choice feeding test showed that termites preferred feeding from the controls when alternative samples were treated with the tannin-boron system. In general the evidence from this study suggests that tannin-boron system can significantly slow down the leaching of boron and it rendered high potential to preserve plywood

L'amélioration des sols est à l'origine une solution économique pour rendre un sol constructible, notamment par rapport aux méthodes de fondations profondes utilisant des pieux. L'amélioration de la compréhension du comportement du matériau provenant de soil-mixing ou jet-grouting connait un intérêt grandissant. Ces deux procédés consistent à mélanger le sol en place avec un liant hydraulique afin de former des colonnes ou des panneaux en "béton de sol". Les fondations spéciales ont connu ces dernières décennies un franc succès aux États-Unis, au Japon et dans les pays Scandinaves. En Europe les nouvelles priorités, pour la plupart liées à l'environnement, au coût de la construction et à la valorisation des matériaux encouragent les industriels à contribuer au développement technologique de la discipline. Certains procédés de mélange paraissent désormais suffisamment sophistiqués pour assurer la réalisation d'éléments structuraux tels que les fondations et les soutènements.Contrairement aux matériaux préfabriqués, à cause des incertitudes liées à l'hétérogénéité des sols, aux conditions environnementales et à la qualité du malaxage sur chantier, il reste toutefois difficile de prédire les propriétés du matériau obtenu. Un manque de règles et de recommandations semble également assez flagrant. Pour répondre au besoin de prédiction et de fiabilisation performantielle des bétons de sol l'objectif des travaux de thèse était donc d'étudier l'influence des paramètres de formulation sur les propriétés physiques et mécaniques du matériau. Les fortes quantités d'eau de gâchage nécessaires à l'obtention d'une consistance de BAP et la faible granulométrie des sols limitent les caractéristiques mécaniques de ces bétons. De par leur composition, les bétons de sol sont donc particulièrement sensibles au retrait de dessiccation et l'importante porosité de ces matériaux les aussi rend plus vulnérables aux agressions chimiques. L’objectif ultime des travaux de recherche était donc de déterminer des paramètres pour une meilleure visibilité de la durée de vie des ouvrages en béton de sol.L'approche béton suivie au laboratoire a consisté à étudier différents bétons de sol composés de sols "artificiels", d'un ciment CEM III/C, et avec un rapport E/C efficace constant. L'étude paramétrique met en évidence un pourcentage volumique d’argile dans le sol au-delà duquel la résistance diminue et la rigidité du matériau peut poser problème pour certaines utilisations structurelles. Les gains de résistance et de rigidité associés à l'augmentation du dosage en ciment sont également quantifiés. Les résultats montrent que l'endommagement par chargement mécanique dépend surtout du dosage en ciment. À partir des résultats expérimentaux, des relations mathématiques sont proposées pour la phase de dimensionnement. Divers essais de vieillissement accéléré permettent de définir des seuils pour les indicateurs de durabilité (porosité et la perméabilité à l'eau). L'analyse de la microstructure du matériau montre aussi l'importance de l'interface pâte-granulat et a permis d'identifier certains mécanismes de dégradation en lien avec les conditions d'exposition. Enfin, ce travail est complété par une étude du comportement à haute température
Soil improvement initially has been used as an economical solution to make soil constructible, particularly in the context of deep foundation methods using piles. There has been growing interest to improve understanding of the behavior of soil-mixing and jet-grouting material, which consist of mixing the soil in place with a hydraulic binder in order to form columns or panels of "soilcrete". In recent decades, these special foundations have had a great success in the United States, Japan and the Scandinavian countries. In Europe, the environmental consciousness and the ongoing trend to reuse existing material to reduce cost of construction are driving companies to contribute to the technological development of this discipline. Some mixing processes now seem to be sophisticated enough to provide structural elements such as foundations and supports.Unlike prefabricated materials, it is difficult to predict the properties of the material obtained through deep soil mixing due to uncertainties related to soil heterogeneity, environmental conditions and the quality of mixing on site. The objective of the thesis work is to address this need for prediction and performantial reliability of soilcrete by studying the influence of the formulation parameters on the physical and mechanical properties of the material. The high quantities of mixing water necessary to obtain a BAP consistency and the small particle size of the soil limit the mechanical properties of the soilscretes and as a consequence, are particularly sensitive to desiccation shrinkage. Besides, the high porosity of these materials also makes them more vulnerable to chemical aggressions. The ultimate objective of the research is to determine parameters for a better visibility of the lifetime of concrete structures in the soil.The approach tested in the laboratory consists of studying different soilcretes composed of "artificial" soils, CEM III / C cement and with a constant W/C ratio. The parametric study reveals a proportion by volume of clay in the soil beyond which the resistance decreases and thus the stiffness of the material can be problematic for some structural uses. The increase in resistance and the associated stiffness of the soilcrete by increasing the cement dosage is also quantified. The results show that the damage by mechanical load depends mostly on the cement dosage. From the experimental results, mathematical relations are proposed for the dimensioning phase. Various tests of accelerated aging help define thresholds for the indicators of durability (porosity and water permeability). The analysis of the microstructure of the material also shows the importance of the paste-aggregate interface and made it possible to identify some mechanisms of degradation in relation to the exposure conditions. To conclude, this work is finalised by a study of the behavior at high temperature

Waste rubber materials are increasing over time with the increase in rubber tire production. These huge piles of waste are contributing to environmental degradation. As such, environment friendly substitutes are required in minimizing the adverse impact. Reuse of these materials in various alternatives are in research for the last few decades; however, major outputs in structural construction material industries are still discouraging. This research primarily focuses on the reuse of crumb rubber in both cement mortar and concrete by replacing 10%, 20%, 30%, 40% and 50% volume of sand aggregates. The experiments and analyses are done in terms of fresh properties, i.e. workability, setting time, and air content as well as hardened characteristics, i.e. compressive strength, splitting tensile strength, flexural strength, stress-strain behavior, unit weight, and water absorption. Moreover, durability aspects, in particular freeze-thaw resistance and rapid chloride permeability test, are examined. The experimental results confirmed low compressive strength of rubber-based mortar; however, crumb rubber up to 10% replacement performed the best with a cement to sand ratio of 1: 2.5. On the other hand, crumb rubber up to 20% replacement in concrete surpassed 35 MPa designated compressive strength, showing comparable results with the control (without any crumb rubber) specimens. Moreover, rubber-based concrete outperformed natural aggregate based concrete in terms of long-term durability performance, creating potentials of using this construction material in harsh environment.
Applied Science, Faculty of
Engineering, School of (Okanagan)
Graduate

Ce travail a pour objectif d'analyser l'utilisation des fibres de lin en substitution aux fibres de verre dans les composites destinés au secteur du nautisme. Cette substitution nécessite une meilleure compréhension du cycle de vie des composites depuis la sélection des matériaux, incluant le procédé de mise en œuvre et jusqu'à leur vieillissement hydrique, principalement sous conditions réelles en service (exposition à l'eau, à la température et aux sollicitations mécaniques). Une étude préliminaire a été consacrée à la sélection des matériaux (tissus de fibre de lin et résine polyester) et à la comparaison entre deux procédés de fabrication des composites (infusion sous vide et thermocompression) sur la base de leurs propriétés morphologiques et mécaniques. Le comportement au vieillissement de composites renforcés de fibres de lin (CRFL) et de composites renforcés de fibres de verre (CRFV) est ensuite étudié. Un ensemble de moyens originaux ont été développés afin de suivre les évolutions de la morphologie (prise en eau, gonflement) et des propriétés mécaniques (statiques et dynamiques). Tout d'abord, le vieillissement hydrothermique des composites à base de fibre de lin et de verre est caractérisé jusqu'à leur saturation en eau. Cette étape est suivie de l'étude de la dessiccation afin de contrôler la réversibilité des propriétés physiques et mécaniques. Parallèlement, une étude particulière de ce travail a été consacrée au traitement des fibres afin de réduire leur hydrophilicité dans le composite. Le couplage hydro-thermo-mécanique est alors analysé en imposant une sollicitation de fluage au biocomposite en immersion. L'application de cette méthodologie révèle l'influence significative des sollicitations couplées. Contrairement à toute attente, la superposition d'une charge au vieillissement hydrothermique ralentit la baisse des propriétés élastiques en comparaison de la somme des effets dus aux vieillissements non-couplés. Enfin un modèle de calcul par éléments finis a été mis au point afin de prédire la diffusion hydrique au sein d'un matériau. Le modèle 2D développé intègre la morphologie réelle du composite et particulièrement l'organisation des fibres de lin dans le composite à plusieurs échelles. Cette modélisation représente la première étape dans la prédiction du comportement évolutif des biocomposites pour des conditions de vieillissement en service
This work aims to address a complete analysis of the use of flax fibres to substitute glass fibres in composite materials designed for nautical applications. This substitution requires a better understanding of the composites life cycle: from materials selection and processing to its hydric ageing, especially under real conditions (exposition to water, temperature and mechanical loadings).A preliminary study is devoted to the selection of materials (flax fibre fabrics and polyester resin) and to the comparison between two methods for manufacturing composites (vacuum infusion and compression moulding) through their mechanical and the morphological properties.The ageing behaviour of flax fibre reinforced composites (FFRC) and glass fibre reinforced composites (GFRC) is then studied. A set of original methods have been implemented to monitor the evolving morphology (water uptake, swelling) and mechanical properties (statics and dynamics). First of all, hydrothermal ageing of glass and flax fibre composites is characterized until water saturation. This step is followed by the study of a drying phase in order to verify the reversibility of physical and mechanical properties. In parallel, a particular issue of this work was devoted to reducing the hydrophilicity of flax fibres into composites.The hydrothermo-mechanical coupling behaviour of biocomposites is then studied by imposing a creep solicitation to biocomposites immersed in water. The application of this methodology highlighted the significant influence of the coupled solicitations. Contrary to all expectations, superimposing a load during a hydrothermal ageing slows the loss of the elastic properties in comparison with the sum of the uncoupled ageing effects.Finally, a finite element model was stablished in order to predict the hydric diffusion within the composite material. The 2D model integrates the real morphology of composites, and particularly the organisation of the flax fibres in the matrix at different scales. This modelling represents the first step in predicting the evolving behaviour of biocomposites exposed to ageing conditions

Coiled springs are one of the important parts providing comfort during driving vehicles. These components highly demand on their fatigue life. This thesis examines the possibility of the influence of surface quality of a spring wire during production process of coiled springs on their mechanical properties and durability.

The phase composition and evolution of the twin structure of PSZ crystals, depending of the concentration stabilizing impurities have been investigated by X-ray diffraction and transmission electron microscopy. The measurements of hardness and fracture toughness by microindentation have been carried out. In work is shown that the high mechanical characteristics of PSZ crystals are related to features of their phase composition and structure, namely the degree of tetragonality the phase and the presence of domains ranging in size from tens to hundreds of nanometers. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/35071

This dissertation is focus on the study of solid-electrolyte interphases (SEIs) on advanced lithium ion battery (LIB) anodes. The purposes of this dissertation are to a) develop a methodology to study the properties of SEIs; and b) provide guidelines for designing engineered SEIs. The general knowledge gained through this research will be beneficial for the entire battery research community.

The phase composition and twin structure of PSZ crystals after heat treatment at 1600 ˚C have been studied in relation to the content of the stabilizing impurity (Y2O3) by X-ray diffraction and transmission electron microscopy. The measurement of both hardness and fracture toughness by microindentation has been carried out. Studies have shown that crystals of PSZ obtained by directional solidification of the melt consist of two tetragonal phases (t and t’), with varying degrees of tetragonality. The yttrium-enriched phase t’ is ‘‘untransformable’’ in contrast to the t phase, with a lower content of yttrium, which, under the influence of mechanical stress, undergoes a martensitic transition to the monoclinic form. Increasing the stabilizing impurity concentration leads to an increase in the volume fraction of the ‘‘untransformable’’ phase. Increasing the concentration of Y2O3 also affects the form and dispersion of the twin domains. In this work it is shown that the quantity of hardening (fracture toughness) is proportional to the content of the transformable t phase. This work was supported by grants from the company "OPTEC" When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/35406

Yes
Cementitious composites are generally brittle and develop considerable tension cracks, resulting in corrosion of steel reinforcement and compromising structural durability. With careful selection and treatment, some kinds of bacteria are able to precipitate calcium carbonate and ‘heal’ cracks in cementitious composites through their metabolism, namely bacterial activity. It is envisioned that the bacterial technology-enabled cementitious composites could have great potential for engineering applications such as surface treatment, crack repair and self-healing construction material. This paper presents the state-of-the-art development of bacterial technology-enabled cementitious composites from the following aspects: mechanisms of bacterial induced calcium carbonate precipitation; methods of applying bacteria into cementitious composites; mechanical properties, durability and their influencing factors; various applications; cost effective analysis and prospect. The paper concludes with an outline of some future opportunities and challenges in the application of bacterial technology-enabled cementitious composites in construction.
National Science Foundation of China (51578110) and the Fundamental Research Funds for the Central Universities in China (DUT18GJ203).

Depuis quelques années, l'industrie automobile s'intéresse au développement d'adhésifs crashs. Ces produits donnent aux assemblages collés des performances exceptionnelles en tenue mécanique statique, en fatigue et en tenue au crash. Ces adhésifs sont formulés pour s'adapter de façon optimale aux procédés de mise en œuvre de l'industrie automobile. L'objectif de l'étude est de déterminer les mécanismes d'adhésion, au cours d'un vieillissement humide, pour différentes chimies de surface et la cinétique des phénomènes engendrant des variations des niveaux d'adhérence et des modes de rupture. Dans cette thèse, des systèmes industriels, le test de traction-cisaillement et le cataplasme humide ont été retenus. Une approche combinant chimie et physique de l'adhésif, de l'acier galvanisé et du joint de colle a été menée. Cette approche multi-technique a permis de mettre en évidence les phénomènes responsables de la perte d'adhérence d'un assemblage acier galvanisé/adhésif crash au cours d'un vieillissement hygrothermique. L'interphase apparaît comme la zone la plus sensible aux contraintes mécaniques avant et après quelques jours de vieillissement. En revanche, pour des temps de vieillissement plus importants, la couche de corrosion devient la zone de faible cohésion. L'étude de l'influence de la chimie de surface des substrats d'acier galvanisé sur les propriétés d'adhérence des assemblages collés montre une meilleure réactivité et donc une meilleure tenue mécanique des substrats contenant davantage de zinc et d'hydroxydes que d'aluminium et d'oxydes. Une attention plus particulière a été portée sur la caractérisation fine de la chimie de surface des aciers galvanisés
Since few years, automotive industry tends to develop crash adhesives. By bonding metal sheets with a continuous bead of crash adhesive, automotive manufacturers can significantly improve both body stiffuess and crashworthiness. The crosslinking conditions of the adhesive on industrial surface (galvanized steel) without cleaning correspond to those used industrially (Electrocoat product). The aim of this work is to determine adhesion mechanisms during hydrothennal ageing for different surface chemistry and kinetics of phenomena generating variations of adhesion levels and failure locus. For this study industrial materials (galvanized steel and epoxy crash adhesive), lap-shear test and humid cataplasm were selected. An approach combining chemistry and physics of the adhesive, substrate and joints was led. This multi-technical approach can be of major interest for the study of phenomena responsible of adhesion loss for adhesively bonded joints in moist environment. So the failure is located in a metal/polymer interphase during the first period of ageing then the failure shifts within a surface layer of corrosion products. The influence of surface chemistry of galvanized steel substrates on metal/polymer adhesion was also studied. The results show a better reactivity and consequently better mechanical properties for substrates with zinc and hydroxides than aluminum and oxides. In this approach, a precise characterization of surface chemistiy was led by XPS methodology

Les enjeux économiques liés à la hausse des coûts des ressources fossiles, leur raréfaction, et les impacts environnementaux inhérents à leur fabrication et à leur utilisation, conduisent les acteurs de la construction à s’orienter vers des matériaux biosourcés. Les ressources issues de la biomasse sont alors au premier plan, celles agricoles notamment, dont les fibres provenant des tiges des plantes. Parmi ces fibres, le lin se démarque en raison de ses propriétés mécaniques élevées et sa faible densité, et sa disponibilité en Normandie. L’objectif de cette étude est de développer un matériau composite innovant par l’association des fibres de lin à une matrice cimentaire, qui sera utilisé dans des procédés de construction préfabriquée. Après la caractérisation fine des constituants de départ, nous avons d’abord décrit en détail l’élaboration des mortiers et bétons biofibrés avec un focus sur la méthodologie de formulation. Puis nous avons analysé l’influence de l’incorporation des fibres de lin sur les propriétés rhéologiques (air occlus, consistance, ouvrabilité et fluidité) et physico-chimiques (pH, ATG). Les propriétés physiques (porosité, module d’élasticité) et mécaniques (contraintes à la rupture, indice de ténacité) ont été mesurées par des essais de flexion et de compression à l’état durci. Ces résultats montrent nettement que la présence des fibres de lin réduit de façon importante les propriétés technologiques des pâtes cimentaires, du fait la sensibilité des fibres au milieu très alcalin et de leur caractère fortement hydrophile. Bien que les traitements de surface des fibres expérimentés (plasma atmosphérique, enrobage coulis de ciment et laitier de hauts fourneaux ou à l’huile de lin) aient permis d’améliorer certaines propriétés des mortiers, ils n’ont pas permis de réduire dans le temps la dégradation des fibres au sein de la matrice cimentaire (hydrolyse alcaline des fibres et leur minéralisation sous l’action de l’hydroxyde de calcium). Il apparaît donc nécessaire de recourir à des liants alternatifs pour tenter d’améliorer la durabilité de ces biocomposites à fibres végétales. Ainsi, de nouvelles formulations de mortiers et bétons sont proposées, dans lesquelles le ciment Portland est remplacé partiellement par le métakaolin / le laitier de hauts fourneaux ou totalement par un ciment sulfo-alumineux, sans préjudices pour le comportement rhéologique. L’étude des nouveaux composites formulés avec le métakaolin ou le ciment sulfo-alumineux indique des niveaux de résistance mécanique et de ténacité élevés. Leurs résistances au gel supérieures au béton classique ou celui incorporant des fibres de verre tient à la forte teneur en air (les fibres jouent un rôle d’agent entraîneur d’air)
The economic issues linked to the rising costs of fossil resources, their scarcity, and the environmental impacts inherent in their manufacture and use, are leading the construction industry to move towards bio-based materials. The resources from biomass are then in the foreground, especially agricultural ones, including fibres from plants stems. Among these fibres, flax stands out because of its high mechanical properties and low density, and its availability in Normandy. The objective of this study is to develop an innovative composite material by combining flax fibres with a cement matrix, which will be used in prefabricated construction processes. After the fine characterization of the initial constituents, we first described in detail the development of plant fibre-reinforced mortars and concretes with a focus on the formulation methodology. Then we analysed the influence of the incorporation of flax fibres on the rheological properties (entrapped air, consistency, workability) and physico-chemical properties (pH, ATG). The physical properties (porosity, modulus of elasticity) and mechanical properties (compressive and tensile strength, toughness index) were measured by bending and compressive tests in the hardened state. These results clearly show that the presence of flax fibres significantly reduces the technological properties of cementitious pastes, because of the sensitivity of the fibres to the highly alkaline medium and their highly hydrophilic nature. The surface treatments of the experimental fibres (by using atmospheric plasma, cement grout coating, blast furnace slag or linseed oil) have effectively improved some properties of mortars, the degradation of the fibres within the cement matrix remain active over the long term (alkaline hydrolysis of the fibres and their mineralization under the action of calcium hydroxide). It therefore appears necessary to use alternative binders in an attempt to improve the durability of these plant fibre biocomposites. Thus, new formulations of mortars and concretes are proposed, in which the Portland cement is partially replaced by metakaolin / blast furnace slag or totally by sulfoaluminate cement, without prejudice to the rheological behaviour. The study of the new composites formulated with metakaolin or sulfoaluminate cement indicates high levels of mechanical strength and toughness. Their resistance to frost superior to conventional concrete or concrete incorporating glass fibres is due to the high air content (the fibres act as an air-entraining admixture)

Nas últimas décadas, a busca pelo desenvolvimento sustentável vem influenciando indústrias de diversos setores a procurar uma destinação correta para os seus resíduos, esta ação visa reduzir os impactos ambientais gerados pelas diversas atividades de cada indústria. Neste sentido, a construção civil se mostra um setor potencial para este emprego, visto a elevada quantidade de matéria-prima de origem natural consumida. No estado do Rio Grande do Sul, onde há a terceira maior produção de pedras preciosas do Brasil, as etapas do beneficiamento de pedras, como a ágata, geram resíduos que requerem solução quanto ao seu destino final. O resíduo de ágata apresenta-se sob três formas: pó, com formato mais arredondado; agregado miúdo, alongado, e a terceira no formato de agregado graúdo, também alongado, todos de coloração clara. No entanto, sempre que se almeja empregar um resíduo, inicialmente é preciso avaliar suas possibilidades de aplicação, frente a questões de sua aplicabilidade técnica, ambiental e econômica. O presente trabalho tem por objetivo estimar a influência dos agregados de ágata, quando substituindo o agregado miúdo de calcário, tradicionalmente utilizado em matrizes cimentícias de cimento Portland branco. O estudo foi desenvolvido iniciando-se pela caraterização dos materiais que foram utilizados, passando posteriormente à realização de ensaios de caracterização de argamassas no estado fresco e no estado endurecido. No estado fresco foram avaliados o índice de consistência e a reologia da mistura, através da reometria rotacional e do squeeze flow. No estado endurecido foram avaliadas as propriedades mecânicas, através dos ensaios de resistência à compressão, resistência à tração por compressão diametral, densidade de massa aparente, módulo de elasticidade dinâmico, e de durabilidade, avaliando a absorção de água por capilaridade e a reação álcali-agregado. Verificou-se influências significativas quanto à substituição dos agregados miúdos por pó de rolagem de ágata. No estado fresco observou-se que as argamassas com pó de rolagem de ágata demandaram maior consumo de água e apresentaram maior plasticidade. Já no estado endurecido, as argamassas produzidas com o agregado miúdo de ágata apresentaram uma resistência à compressão e resistência à tração na compressão diametral inferior quando comparadas às argamassas produzidas com calcário, com diferentes relações água aglomerante. Além disso, as argamassas produzidas com agregado miúdo de ágata apresentaram densidade de massa aparente e módulo de elasticidade inferior quando comparada com as argamassas com agregado miúdo de calcário. Quanto à absorção de água por capilaridade, as argamassas produzidas com pó de rolagem de ágata apresentaram menor índice de absorção, com exceção dos traços produzidos sem pó de rolagem de ágata, onde o calcário apresentou uma menor absorção de água por capilaridade. No ensaio de reação álcali-agregado, o agregado miúdo de ágata foi considerado reativo, no entanto a combinação entre este agregado e o pó de rolagem de ágata gerou resultados inócuos.
In recent decades, the demand for sustainable development has been influencing industries from many sectors to seek a proper destination for their waste. The use of waste for other purposes aims to reduce the environmental impacts. In this context, the civil construction industry is a potential sector for this use, since the high amount of natural raw material used, being a viable alternative to reduce their environmental impact. Thus, in the state of Rio Grande do Sul, where there is the third largest production of precious stones of Brazil, processing stages of the stones, such as agate, generate waste that requires solution in relation to its final destination. Agate residues are found in three different forms: powder, with rounded shape; fine aggregate, with elongated shape, and coarse aggregate, also with elongated shape, all light-colored. The use of waste requires knowledge of their application possibilities, trying to evaluate the feasibility of its use in the technical, environmental and economic point of view. The objective of this study was to evaluate the influence of the use of agate aggregates in mortar for white concrete, replacing limestone fine aggregate, usually employed in cementitious matrices of white Portland cement. The study started with the characterization of the materials that were used and conducting to perform the tests in fresh and hardened state. The samples in fresh state were investigated by consistency index and squeeze flow. In the hardened state, samples were subjected to compression tests, tensile strength in diametrical compression, bulk density, dynamic modulus of elasticity, and also durability tests were used to evaluate the absorption of water by capillarity and the alkali-aggregate reaction. The results have shown significant influences in the substitution of fine aggregates by agate powder. In the fresh state it was observed that the mortars with agate powder required higher consumption of water and had better plasticity. In the hardened state, it was observed that mortars with agate fine aggregate showed lower compressive and tensile strength in diametrical compression, bulk density and modulus of elasticity compared to mortars made with limestone. In addition, the mortars produced with agate powder showed lower absorption of water by capillarity, except for mixtures produced without agate powder, where the limestone causes a lower water absorption by capillarity. In the alkali-aggregate reaction the agate fine aggregate can be considered reactive. However, the combination of this aggregate and agate powder can be considered innocuous.

L'objectif est de mieux connaître les diverses propriétés (physico-mécaniques, biologiques et chimiques) du bois de Mûrier blanc (Morus alba L.), en tant que matériau éminemment utilisé dans la fabrication de luths Iraniens. La différence de caractéristiques vibratoires de cette espèce a été mesurée en fonction de la présence d'extractibles, mais aussi pour trois traitements artisanaux qui ont été adaptés à l'échelle du laboratoire.Le bois Mûrier blanc est caractérisé par un module spécifique modéré, un amortissement plus bas que prévu et une anisotropie faible entre ses trois axes. Il est précisé que cette espèce ne peut pas être classifiée avec les mêmes normes que les autres bois utilisés pour les instruments classiques Européens. En utilisant les deux extractions indépendantes et successives, il est révélé que l'amortissement est régi par deux types d'extraits, certains l'abaissent et certains l'augmentent. Ces composés ne sont pas tous extractibles par les mêmes solvants. L'immersion de longue durée dans une eau à température ambiante ne modifie pas les propriétés mécaniques de l'espèce, toutefois, elle peut laisser le bois avec des défauts irréversibles. Un court traitement à l'eau chaude (70°C) entraîne l'augmentation de l'amortissement et la diminution du module spécifique. Dans ce dernier cas, des modifications sont presque progressives avec le temps.Le bois de Mûrier blanc semble être « très durable » par rapport à une attaque fongique, même dans des conditions extrêmes. Le délavage dans l'eau n'a pas d'effets sur la résistance de cette espèce contre basidiomycètes. Ce bois est classé « moyennement durable » contre l'attaque des termites et devient sensible après le délavage. Ses extractibles ont donc des effets toxique sur les termites. Les phénols, acides gras, stérols, hydrocarbures supérieurs, et composés aromatiques sont les composés présents dans les extraits de cette espèce. Le résorcinol, composé prédominant trouvé dans l'espèce, a été récemment rapporté comme la cause de plusieurs problèmes de santé, ce qui est aujourd'hui observé chez les artisans Iraniens
This work aims at studying the several divers properties (Physico-mechanical, biological and chemical) of white Mulberry (Morus alba L.), as the leading material used in fabrication of Iranian lutes. The vibrational characteristic of this species is measured in relation with secondary metabolites (extractives) as well as three artisanal hygro-thermal treatments adapted to laboratory scale.White Mulberry wood is characterized with a moderate specific modulus, less than expected damping and a low anisotropy between three directions. It is specified that this species cannot be described with the same standards as other woods used in European classical instruments. Using independent and successive extractions reveal that two types of extraneous compounds govern the damping in this wood, some raising it, when the rest have a decreasing effect. These compounds are not all extractable by the same solvents.Long time immersion in water at ambient temperature hardly changes mechanical properties of the species, however, it can leave wood with irreversible defects. Hot water treatment at 70°C results for damping and moduli to be increased and decreased respectively. These changes are time related. Several mild desorption and adsorption cycles, seem to reduce damping without greatly endangering the moduli. White Mulberry wood is found to be very durable towards fungi, even in extreme conditions. Water leaching seems to be affectless on this species resistance towards basidiomycetes. This wood is rated moderately durable towards termites and becomes sensible after water leaching. Extractives seem to play important role in this wood natural resistance, as they are found to have toxic effect on termites. Resorcinol, a phenol, is the leading compound in the extractives of white Mulberry. Fatty acids, sterols, higher hydrocarbons, and aromatic compounds are also found as the constituents of secondary metabolites. Resorcinol is documented to cause irritations close to what is normally experienced by the fabricants working with white Mulberry for a long time

In order to meet the need of metallurgical industry in the world, a new MgAlON-BN composite which can be used for example in special refractory nozzles, tubes and break rings for the continuous casting of steel was studied in the present thesis. The aim was to understand the mechanism of synthesis and their physicochemical properties during the application. Thus, the thermodynamic properties, synthesis process, mechanical properties, thermal shock behaviour, thermal diffusivity/conductivity as well as corrosion resistance to molten iron containing oxygen and molten slag of MgAlON and MgAlON-BN composites have been investigated. The Gibbs energy of formation of MgAlON was estimated using the method proposed by Kaufman. The phase stability diagram of Mg-Al-O-N-B was investigated, and consequently the synthesis parameters were determined. MgAlON and MgAlON-BN composites were fabricated by hot-pressing method. The composites obtained this way were characterized by XRD, SEM, TEM and HREM analyses. A Matrix-flushing method was employed in the quantitative XRD analysis for the multi-component samples to understand the mechanism of synthesis. The relationship between mechanical properties and microstructure of the composites was investigated. The experimental results indicated that BN addition has significant influence on the mechanical properties of the composites. These can be explained by the fact that BN has low Young’s modulus, density and non-reactive nature as well as considerable anisotropy of many properties such as thermal expansion, thermal diffusivity/conductivity. Thus, the addition of BN in MgAlON is likely to lead to the presence of microcracks caused by the mismatch of thermal expansion coefficient. The microcracks result in the enhancement of the strength at elevated temperature and thermal shock durability of the composites. Effective thermal conductivities were evaluated from the present experimental results of thermal diffusivities, heat capacity and density. A model suitable for present composites has been derived based on Luo’s model. The predicted lines calculated by the model were in good agreement with experimental results. The reactions between the composites and molten iron as well as the slag were investigated by ‘‘finger’’ experiments and sessile drop experiments. Both experimental results indicated that the BN addition has positive influence on the corrosion resistance. These are attributed to the excellent corrosion resistance of BN to molten iron and slag, such as the higher contact angle between BN substrate and liquid iron and molten slag compared with that obtained for pure MgAlON.
QC 20100929

Submitted by CARLA MARIA GOULART DE MORAES (carlagm) on 2015-05-07T15:29:04Z No. of bitstreams: 1 MicheliSilveiraGoncalves.pdf: 3809253 bytes, checksum: 08117d13836ff905179bd2fbdae30d28 (MD5)
Made available in DSpace on 2015-05-07T15:29:04Z (GMT). No. of bitstreams: 1 MicheliSilveiraGoncalves.pdf: 3809253 bytes, checksum: 08117d13836ff905179bd2fbdae30d28 (MD5) Previous issue date: 2011-03-25
CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
PROSUP - Programa de Suporte à Pós-Gradução de Instituições de Ensino Particulares
A preocupação com o meio ambiente e a escassez de recursos naturais tem levado à busca por alternativas de crescimento mais sustentáveis por parte de todos os segmentos da sociedade. Dentro desta corrida pelo bem estar ambiental, a reciclagem de resíduos tem se mostrado uma boa alternativa na redução do impacto causado pelo consumo desordenado de matéria-prima e pela redução das áreas de disposição, em virtude do grande volume de resíduos descartados a cada ano em todo mundo. Neste contexto encontram-se inseridos os resíduos da construção civil, foco deste trabalho, o qual tem como objetivo o estudo da influência da utilização de agregados reciclados de concreto para a produção de novos concretos e à verificação da potencialidade de reciclagem dos resíduos gerados pela indústria de pré-fabricados em concreto localizada no município de Porto Alegre. Para as novas matrizes de concreto confeccionaram-se três traços, com os dois resíduos gerados em maior quantidade pela indústria, sendo realizada a substituição do agregado graúdo natural pelo reciclado de concreto na quantidade de 50% em volume. Utilizou-se água de compensação na confeccção dos concretos com agregado reciclado devido as diferentes absorções de água. Nestes novos concretos verificou-se a influência do agregado reciclado sobre as propriedades mecânicas (resistência à compressão e à tração), propriedade de durabilidade (absorção de água) e observado o monitoramento da evolução da temperatura das reações de hidratação. A partir dos resultados obtidos realizaram-se análises estatísticas e apresentaram-se modelos matemáticos. Concluindo-se que os concretos confeccionados com ARCs, oriundos do processo de cura convencional, apresentaram acréscimo nas propriedades de resistência à compressão e à tração, enquanto os oriundos do processo de cura térmica, decréscimo quando comparados à referência. Já para a propriedade de absorção de água, verificou-se um aumento para os dois tipos de ARCs, quando compara-se à referência, não sendo este aumento significativo em escala real. Para o monitoramento da evolução da temperatura das reações de hidratação da pasta do concreto, verificou-se redução do início dos tempos, para as amostras contendo agregado reciclado, sem a presença de aditivo, ao comparar-se à referência, já para as amostras com aditivo, verificou-se maiores valores de temperatura, não sendo observada nenhuma tendência quanto ao início e fim dos tempos de evolução da temperarura das reações de hidratação das amostras de concreto.
The concern about the environment and the lack of natural resources has led all segments of society to the search for more sustainable alternatives of growth. In this run for environmental welfare, the recycling of material waste seems to be a good alternative for the reduction of the impact caused by the messy consumption of raw material and the reduction of provision areas, by virtue of the great amount of discarded waste every year in the world. In this context is the waste coming from civil construction, the focus of this work, which aims to study the influence of the use of recycled concrete aggregate for the production of new concrete and also the verification of the recycling potential of the waste generated by the industry ofprecast concrete located in the city of Porto Alegre. For new concrete matrixes crafted three traces, with the two waste materials generated in most part by the industry, having the replacement of the natural coarse aggregate been done with the recycled concrete in the volume of 50%. Compensation water was used in the making of concrete with recycled aggregate due to different levels of water absorption. In this new concrete was checked the influence of the recycled aggregate over the mechanical properties (resistance to compression and traction), durability property (water absorption) and was observed the monitoring of the evolution of temperature of the hydration reactions. From the results obtained, statistical analyses and mathematical models were made. It can be concluded that the concrete manufactured with RCAs (recycled concrete aggregate) coming from the conventional cure process showed increase in the properties of resistance to compression and to traction, while the ones coming from the process of thermal cure show decrease when compared to the reference. As for the property of water absorption, there is an increase for both kinds of RCAs when compared to the reference, not constituting a significant increase in real scale. For the monitoring of the temperature evolution of the hydration reactions of the concrete paste was verified decrease of the beginning of time for samples containing recycled aggregate without the presence of additive, when compared to the reference, was verified higher values of temperature, not having been observed any tendency regarding as start and end times for the evolution of temperarure the reactions of hydration of concrete samples.

Bien que déjà présentées comme une technologie sûre et propre, les piles à combustible à membrane échangeuse de protons (PEMFC) restent confrontées à de solides verrous en termes de durabilité et de fiabilité, limitant leur commercialisation à large échelle. De nombreuses études ont déjà permis d’affiner la compréhension des phénomènes de vieillissement et ont permis de désigner la dégradation de la membrane comme l’un des principaux facteurs limitant la durée de vie des PEMFC. Cette étude vise à apporter des éléments de compréhension sur les mécanismes de dégradations chimique et mécanique par l’intermédiaire de protocoles de vieillissement ex-situ, ainsi qu’à comprendre l’impact de ces dégradations sur la structure et les propriétés fonctionnelles des membranes. Dans un premier temps, il a été nécessaire de clarifier l’influence de la réaction de Fenton, un protocole de vieillissement ex-situ largement reconnu dans la littérature, sur la dégradation chimique des membranes Nafion™. Les résultats ont confirmé que la concentration en réactifs de Fenton influençait significativement la décomposition chimique du polymère, à la fois d’un point de vue chimique et morphologique. Par la suite, nous avons choisi de suivre l’évolution de la dégradation chimique des membranes Nafion™ en fonction du temps et d’étudier son impact sur la structure de la membrane, ses propriétés de sorption et de diffusion de l’eau ainsi que son fonctionnement en pile. À cet égard, différentes techniques de caractérisation telles que la spectroscopie RMN 19F ou 1H ainsi que la spectroscopie FTIR ont permis de corréler les propriétés physico-chimiques de la membrane à ses caractéristiques structurelles et de mettre ainsi en évidence plusieurs marqueurs de la dégradation chimique. Enfin, un dispositif sur-mesure a été conçu afin d’étudier l’impact des contraintes mécanique et chimique conjointes sur les membranes Nafion™. L’objectif de ce dispositif était de reproduire des conditions de vieillissement proches de celles rencontrées lors du fonctionnement en pile
Although proton-exchange membrane fuel cells (PEMFC) are nowadays considered as a safe and clean energy technology, they still suffer from durability and reliability issues restricting their widespread commercialization. Innumerable studies have already led to a better understanding of aging phenomena and highlighted membrane degradation as one of the main factors limiting PEMFC lifetime. This study aims at bringing some clarifications on the chemical and mechanical degradation mechanisms of membranes through ex-situ aging protocols as well as understanding the impact of these degradations on the membrane structure and functional properties. First, it was necessary to clarify the influence of Fenton’s reaction, an ex-situ aging protocol widely recognized in the literature, on the chemical degradation of Nafion™ membranes. The results confirmed that Fenton’s reagents concentration significantly influenced polymer chemical decomposition, both from a chemical and morphological point of view. Subsequently, we chose to monitor the evolution of pure chemical degradation of Nafion™ membranes as a function of time and to study its impact on the membrane structure, water sorption and diffusion properties, as well as operability in fuel cells. In that respect, various characterization techniques such as 19F or 1H-NMR as well as FTIR spectroscopies allowed us to correlate physico-chemical properties of the membrane to its structural characteristics and to thus highlight several indicators of chemical degradation. Finally, a custom-made device has been developed to study the impact of conjoint mechanical and chemical stress on Nafion™ membranes. The objective of this device was to replicate aging conditions close to those encountered during fuel cell operation

Wood plastic composites (WPCs) were made using matrices of recycled high-density polyethylene (rHDPE) and polypropylene (rPP) with sawdust (Pinus radiata) as filler. Corresponding WPCs were also made using virgin plastics (HDPE and PP) for comparison with the recycled plastic based composites. WPCs were made through melt compounding and hot-press moulding with varying formulations based on the plastic type (HDPE and PP), plastic form (recycled and virgin), wood flour content and addition of coupling agent. The dimensional stability and mechanical properties of WPCs were investigated. Durability performances of these WPCs were studied separately, by exposing to accelerated freeze-thaw (FT) cycles and ultraviolet (UV) radiation. The property degradation and colour changes of the weathered composites were also examined. Dimensional stability and flexural properties of WPCs were further investigated by incorporation of nanoclays in the composite formulation. To understand the changes in WPCs stability and durability performance, microstructure and thermal properties of the composites were examined. Two mathematical models were developed in this work, one model to simulate the moisture movement through the composites in long-term water immersion and the other model to predict the temperature profile in the composites during hot-press moulding. Both rHDPE and rPP matrix based composites exhibited excellent dimensional stability and mechanical properties, which were comparable to those made from virgin plastics. Incorporation of maleated polypropylene (MAPP) coupling agent in composite formulation improved the stability and the mechanical properties. The incorporation of 3 wt. % MAPP coupling agent to WPCs showed an increase in tensile strength by 60% and 35 %, respectively, for the rHDPE based and rPP based composites with 50 wt. % wood flour. Scanning electron microscopy (SEM) images of the fractured surfaces of WPCs confirmed that the MAPP coupling improved the interfacial bonding between the plastic and the wood filler for both series of composites. Long-term water immersion tests showed that the water transport mechanism within the WPCs follows the kinetics of Fickian diffusion. Dimensional stability and flexural properties of the WPC were degraded after 12 accelerated FT cycles as well as 2000 h of UV weathering for both recycled and virgin HDPE and PP based composites. However, the MAPP coupled composites had improved stability and flexural property degradation. The surface of the weathered composites experienced a colour change, which increased with the exposure time. The MAPP coupled composites exhibited less colour change as compared to non-coupled composites. Regarding the effect of the plastic type, the PP based composites experienced higher colour change than those based on HDPE. With weathering exposure, flexural strength and stiffness of the WPCs were decreased, but elongation at break was increased regardless of plastic type and wood flour content. MAPP coupled rPP and rHDPE based UV weathered WPCs lowered the degradation of stiffness by 50% and 75%, respectively compared to non-coupled WPCs. SEM images of the fractured surfaces of FT and UV weathered WPCs confirmed a decrease in the interfacial bonding between the wood flour and matrix. Thermal properties of weathered composites changed with weathering, but the extent of the changes depended on WPCs formulation and matrix type. From the experimental studies on nanoclay-filled rHDPE composites, it is found that stability, flexural properties of WPCs could be improved with an appropriate combination of coupling agent, and nanoclay contents processed by melt blending. Incorporation of 1-5 wt. % nanoclay in the maleated polyethylene (MAPE) coupled wood plastic composite improved the dimensional stability and flexural properties. The thermal properties changed with the addition of nanoclay and MAPE in WPCs. In this work, a hot press-moulding model was proposed based on the one-dimensional transient heat conduction to predict the temperature profile of the WPCs during hot pressing cycle. The results from this work clearly show that rHDPE and rPP can be successfully used to produce stable and strong WPCs, which properties and performances are similar to or comparable to composites made of wood and virgin plastics. Therefore, WPCs based on recycled PP and HDPE matrix could have potential to use as construction materials.

O desenvolvimento do concreto de alta resistência - CAR foi um importante avanço na tecnologia de concreto, entretanto, a despeito de suas inúmeras vantagens como material estrutural, o seu emprego tem sido limitado, por ter se revelado mais susceptível à fissuração nas primeiras idades. Isto se deve à ocorrência do fenômeno da retração autógena, particularmente mais intenso nestes concretos que nos de resistência normal, uma vez que no CAR, há significativamente maior quantidade de material cimentício e menor quantidade de água, o que dá origem a uma estrutura porosa muito refinada logo nas primeiras idades, gerando altas magnitudes de tensões capilares. Além do estudo sobre o entendimento do fenômeno, as pesquisas atualmente têm buscado formas de mitigá-lo a fim de contribuir para estruturas mais duráveis. Diante do exposto, esta pesquisa investigou o comportamento do CAR, no tocante às propriedades mecânicas, elásticas e viscoelásticas e à durabilidade, quando empregado um aditivo redutor de retração - ARR que pode se configurar como estratégia mitigadora para a redução da retração autógena, bem como verificar a sua influência sobre a microestrutura e hidratação da pasta de cimento. Os resultados indicam que o ARR é eficaz na redução da retração autógena e retração por secagem, sem alterar de forma relevante as propriedades mecânicas e elásticas: a resistência à compressão sofre uma pequena queda de 5% com o uso de 2% de ARR em relação ao concreto referência, contudo, as demais propriedades não são alteradas com o uso do ARR. Quanto ao efeito sobre a fluência, não se obtiveram resultados conclusivos. A durabilidade, medida pelos ensaios de penetrabilidade a íons cloretos, permeabilidade à água, carbonatação natural e absorção capilar e por imersão, não é comprometida com a incorporação do aditivo redutor de retração. Do ponto de vista microestrutural, observou-se que o ARR altera o volume total de poros, embora de uma forma não muito expressiva; e ainda constatou-se que este aditivo afeta a velocidade de hidratação das pastas de cimento, e que possivelmente interage com compostos de hidratados da pasta, sem, no entanto, alterar as características macroestruturais do material.
The development of high strength concrete - HSC represented an important advance in concrete technology. However, even knowing that this kind of concrete has several advantages as a structural material, its application is limited by the early ages cracking. This occurrence is due to the autogenous shrinkage phenomenon, once HSC has a greater amount of cementitious material and a lower amount of water in relation to a normal-strength concrete. This condition implies in a greatly refinement of pore structure at early ages which lead to a higher magnitudes of capillary tension than the one observed in a normal-strength concrete. Beyond to study the phenomenon, much research has been conducted in many countries in order to reduce autogenous shrinkage and contribute to more durable structures. So, this research aims to investigate the effectiveness of shrinkage-reducing admixtures – SRA in decreasing the autogenous shrinkage of HSC, and mainly, verify its influence on viscoelastic, elastic and mechanicals properties and durability. The effect of SRA on microstructure and on the cement paste hydration was also investigated. The results show that SRA is effective in reducing the autogenous shrinkage and drying shrinkage without remarkable changes in elastic and mechanical properties. There were not conclusive results related to the creep property. The concrete durability under the action of aggressive agents (such as water, CO2 and chloride) was not influenced by the SRA, information provided by the results of chloride penetration, natural carbonation, water permeability, capillary absorption and absorption of water tests. In a microstructural point of view, it was observed that the addition of SRA results in a small rise in total pore volume. Besides, the results suggest that the SRA affects the rate of cement hydration and it can interact to the hydrated products of paste without implying in great influences on the macrostructural characteristics of the material.

The diploma thesis is focused on the behaviour of natural and synthetic aggregates and their behaviour in polymer – cement composites, while being exposed to high temperature. The processes, happening in aggregates and mortar under the thermal load, were described in the theoretical part of the thesis same as the testing of heat effects on the aggregates and mortar. Further, the influence of high temperature on each component of concrete was described, followed by the suggestion of the appropriate components for concrete exposed to high temperature. Various aggregates were tested in the experimental part of the thesis. The basic physical and mechanical properties of aggregates were examined same as their mineralogical composition with using XRD, DTA and SEM methods. At the mortar, the influence of high temperature on the concrete density, compressive strength and tensile strength was defined. The gained knowledge was evaluated in the final part of the thesis

Interfaces et durabilité des électrodes de pointe pour l'énergie (PAC et EHT)L'objectif de cette thèse concerne l'élaboration, par atomisation électrostatique, d'une électrode à oxygène à architecture innovante, basée sur un composite Ce0.9Gd0.1O1.95 (CGO) - La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) possédant un gradient de composition ou une composition homogène. Cette électrode a été déposée sur un substrat de zircone yttriée (YSZ = 8 % mol. Y2O3-ZrO2) sur laquelle, a été intercalée au préalable une couche barrière mince et dense de CGO. Cette électrode possède une microstructure innovante, à porosité élevée permettant d'obtenir une grande surface active qui devrait conduire à l'amélioration des performances électrochimiques. Le comportement électrique de l'électrode a été étudié par spectroscopie d'impédance en fonction de la température et sous air. Une description microstructurale détaillée a été effectuée à l'aide d'un modèle de reconstruction 3D obtenu par -MEB équipé d'une sonde ionique focalisée et par nanotomographie X. Ces propriétés microstructurales ont été reliées aux propriétés électriques. Les propriétés mécaniques et tribologiques de cette électrode composite ont été déterminées par des tests du scotch et ultra-microindentation. Finalement, des tests de durabilité ont été effectués sur une électrode de grande taille possédant une surface active de 45 cm2 jusqu'à 800 h à environ 770°C, dans une cellule complète de configurations PAC et fonctionnant respectivement sous H2 et un mélange H2/H2O
Interfaces and durability of advanced electrodes for energy (IT-SOFC and SOEC)The objective of this PhD thesis is to fabricate advanced oxygen electrode based on Ce0.9Gd0.1O1.95 (CGO) and La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) with graded and homogeneous composition onto yttria-stabilized zirconia (YSZ = 8 mol. % Y2O3-doped ZrO2) electrolyte using electrostatic spray deposition. A thin and dense layer of CGO was inserted between LSCF and YSZ to serve as a barrier diffusion layer. The novel microstructure with high porosity and large surface area is expected to improve the electrochemical performances. The electrical behavior of the electrode was investigated by impedance spectroscopy versus temperature in air. A detailed microstructural description was performed by 3D reconstructed model from FIB-SEM and X-ray nanotomography and related to electrical properties. The mechanical analysis was performed by scratch and ultramicroindentation tests. Finally, durability tests were performed on the electrode with 45 cm2 oxygen active area, up to 800 h at around 770°C, in full cell SOFC and SOEC configurations operating respectively in H2 and H2/ H2O mixture

Les composants d’électronique de puissance ont (et vont encore avoir !) eu une grande influence sur les secteurs de l'énergie et des transports. Ces pièces sont notamment constitués d’assemblages céramique –cuivre pour lesquels la tenue mécanique doit être maîtrisée afin de garantir dans le future une durabilité d’environ 30 ans sous l’action de cycles thermiques plus en plus grande. Une analyse des mécanismes de défaillance des assemblages DBC (Direct Bonding Copper) utilisés en électronique de puissance est étudiée (le délaminage le long de l’interface cuivre -céramique et/ou la rupture fragile de la céramique). Pour identifier le comportement élastoplastique du cuivre, nous avons montré qu’il est nécessaire d’utiliser une plaque de cuivre ayant subi l’ensemble des traitements thermiques liés au processus d’assemblage. Le comportement élastique fragile de la céramique est décrite dans le cadre d’une statistique de Weibull. Dès lors, une caractérisation du délaminage cuivre-céramique sous flexion quatre points a permis d’identifier un modèle cohésif pour l’interface. La calibration des paramètres cohésifs est menée en utilisant les données à deux échelles : i) macroscopique de force-déplacement ii) locale de suivi optique de la fissuration avec le déplacement imposé. L’intégrité mécanique des assemblages DBC pour différentes épaisseurs des couches de cuivre et de céramique a été étudié. Nous avons montré que les configurations avec un rapport proche de l’unité sont les plus dangereuses en engendrant un délaminage, qui se poursuit sous cyclage thermique. Ce dernier peut être notablement réduit en structurant le pourtour de la surface de cuivre avec des trous cylindriques répartis périodiquement. Ainsi, un modèle éléments finis permettant d’évaluer les assemblages les plus prometteurs en terme de durabilité a été établie. En l’absence de défauts géométrique, la couche de cuivre reste intègre, même dans le cas d’un délaminage dont le front induit une concentration de contrainte
The power electronics components (and still will have!) have a great influence on the energy and transport sectors. These parts are made of ceramic-copper assemblies for which the mechanical strength must be controlled to ensure durability about 30 years under the thermal cycles increasingly larger. A failure mechanisms analysis in DBC (Direct Copper Bonding) assemblies used in power electronics is studied (the delamination along the interface copper - ceramic and/or the brittle ceramic fracture). To identify the elastoplastic behavior of copper, we showed that it’s necessary to use a copper plate having undergone the heat hole treatments related to the assembly process. The ceramic gragile elastic behavior is descrobed within the Weibull statictics framework. Consequently, a copper-ceramic delamination characterization under four points bending made it possible to identify a cohesive model for the interface. The cohesive calibration parameters is carried out by using the data in two scales: i) strentgh-displacement macroscopic ii) local cracking optical follow-up with imposed displacement. The mechanical integrity of DBC assemblies of different thickness of copper and ceramic has been studied. We showed that the configurations with a ratio close to the unit are most dangerous by generating a delamination, which continues under thermal cycling. This risk of delamination can be notably reduced by structuring the copper circumference surface with cylindrical holes distributed periodically. Thus, a finite elements model allowing us to evaluate the most promising assemblies in term of durability, was estabilshed. In the absence of geometrical defects, the copper layer must remains, even in the delamination case whose face induces a concentration stress

Le béton conventionnel (BC) a de nombreux problèmes tels que la corrosion de l’acier d'armature et les faibles résistances des constructions en béton. Par conséquent, la plupart des structures fabriquées avec du BC exigent une maintenance fréquent. Le béton fibré à ultra-hautes performances (BFUP) peut être conçu pour éliminer certaines des faiblesses caractéristiques du BC. Le BFUP est défini à travers le monde comme un béton ayant des propriétés mécaniques, de ductilité et de durabilité supérieures. Le BFUP classique comprend entre 800 kg/m³ et 1000 kg/m³ de ciment, de 25 à 35% massique (%m) de fumée de silice (FS), de 0 à 40%m de poudre de quartz (PQ) et 110-140%m de sable de quartz (SQ) (les pourcentages massiques sont basés sur la masse totale en ciment des mélanges). Le BFUP contient des fibres d'acier pour améliorer sa ductilité et sa résistance aux efforts de traction. Les quantités importantes de ciment utilisées pour produire un BFUP affectent non seulement les coûts de production et la consommation de ressources naturelles comme le calcaire, l'argile, le charbon et l'énergie électrique, mais affectent également négativement les dommages sur l'environnement en raison de la production substantielle de gaz à effet de serre dont le gas carbonique (CO[indice inférieur 2]). Par ailleurs, la distribution granulométrique du ciment présente des vides microscopiques qui peuvent être remplis avec des matières plus fines telles que la FS. Par contre, une grande quantité de FS est nécessaire pour combler ces vides uniquement avec de la FS (25 à 30%m du ciment) ce qui engendre des coûts élevés puisqu’il s’agit d’une ressource limitée. Aussi, la FS diminue de manière significative l’ouvrabilité des BFUP en raison de sa surface spécifique Blaine élevée. L’utilisation du PQ et du SQ est également coûteuse et consomme des ressources naturelles importantes. D’ailleurs, les PQ et SQ sont considérés comme des obstacles pour l’utilisation des BFUP à grande échelle dans le marché du béton, car ils ne parviennent pas à satisfaire les exigences environnementales. D’ailleurs, un rapport d'Environnement Canada stipule que le quartz provoque des dommages environnementaux immédiats et à long terme en raison de son effet biologique. Le BFUP est généralement vendu sur le marché comme un produit préemballé, ce qui limite les modifications de conception par l'utilisateur. Il est normalement transporté sur de longues distances, contrairement aux composantes des BC. Ceci contribue également à la génération de gaz à effet de serre et conduit à un coût plus élevé du produit final. Par conséquent, il existe le besoin de développer d’autres matériaux disponibles localement ayant des fonctions similaires pour remplacer partiellement ou totalement la fumée de silice, le sable de quartz ou la poudre de quartz, et donc de réduire la teneur en ciment dans BFUP, tout en ayant des propriétés comparables ou meilleures. De grandes quantités de déchets verre ne peuvent pas être recyclées en raison de leur fragilité, de leur couleur, ou des coûts élevés de recyclage. La plupart des déchets de verre vont dans les sites d'enfouissement, ce qui est indésirable puisqu’il s’agit d’un matériau non biodégradable et donc moins respectueux de l'environnement. Au cours des dernières années, des études ont été réalisées afin d’utiliser des déchets de verre comme ajout cimentaire alternatif (ACA) ou comme granulats ultrafins dans le béton, en fonction de la distribution granulométrique et de la composition chimique de ceux-ci. Cette thèse présente un nouveau type de béton écologique à base de déchets de verre à ultra-hautes performances (BEVUP) développé à l'Université de Sherbrooke. Les bétons ont été conçus à l’aide de déchets verre de particules de tailles variées et de l’optimisation granulaire de la des matrices granulaires et cimentaires. Les BEVUP peuvent être conçus avec une quantité réduite de ciment (400 à 800 kg/m³), de FS (50 à 220 kg/m³), de PQ (0 à 400 kg/m³), et de SQ (0-1200 kg/m³), tout en intégrant divers produits de déchets de verre: du sable de verre (SV) (0-1200 kg/m³) ayant un diamètre moyen (d[indice inférieur 50]) de 275 µm, une grande quantité de poudre de verre (PV) (200-700 kg/m³) ayant un d50 de 11 µm, une teneur modérée de poudre de verre fine (PVF) (50-200 kg/m³) avec d[indice inférieur] 50 de 3,8 µm. Le BEVUP contient également des fibres d'acier (pour augmenter la résistance à la traction et améliorer la ductilité), du superplastifiants (10-60 kg/m³) ainsi qu’un rapport eau-liant (E/L) aussi bas que celui de BFUP. Le remplacement du ciment et des particules de FS avec des particules de verre non-absorbantes et lisse améliore la rhéologie des BEVUP. De plus, l’utilisation de la PVF en remplacement de la FS réduit la surface spécifique totale nette d’un mélange de FS et de PVF. Puisque la surface spécifique nette des particules diminue, la quantité d’eau nécessaire pour lubrifier les surfaces des particules est moindre, ce qui permet d’obtenir un affaissement supérieur pour un même E/L. Aussi, l'utilisation de déchets de verre dans le béton abaisse la chaleur cumulative d'hydratation, ce qui contribue à minimiser le retrait de fissuration potentiel. En fonction de la composition des BEVUP et de la température de cure, ce type de béton peut atteindre des résistances à la compression allant de 130 à 230 MPa, des résistances à la flexion supérieures à 20 MPa, des résistances à la traction supérieure à 10 MPa et un module d'élasticité supérieur à 40 GPa. Les performances mécaniques de BEVUP sont améliorées grâce à la réactivité du verre amorphe, à l'optimisation granulométrique et la densification des mélanges. Les produits de déchets de verre dans les BEVUP ont un comportement pouzzolanique et réagissent avec la portlandite générée par l'hydratation du ciment. Cependant, ceci n’est pas le cas avec le sable de quartz ni la poudre de quartz dans le BFUP classique, qui réagissent à la température élevée de 400 °C. L'addition des déchets de verre améliore la densification de l'interface entre les particules. Les particules de déchets de verre ont une grande rigidité, ce qui augmente le module d'élasticité du béton. Le BEVUP a également une très bonne durabilité. Sa porosité capillaire est très faible, et le matériau est extrêmement résistant à la pénétration d’ions chlorure (≈ 8 coulombs). Sa résistance à l'abrasion (indice de pertes volumiques) est inférieure à 1,3. Le BEVUP ne subit pratiquement aucune détérioration aux cycles de gel-dégel, même après 1000 cycles. Après une évaluation des BEVUP en laboratoire, une mise à l'échelle a été réalisée avec un malaxeur de béton industriel et une validation en chantier avec de la construction de deux passerelles. Les propriétés mécaniques supérieures des BEVUP a permis de concevoir les passerelles avec des sections réduites d’environ de 60% par rapport aux sections faites de BC. Le BEVUP offre plusieurs avantages économiques et environnementaux. Il réduit le coût de production et l’empreinte carbone des structures construites de béton fibré à ultra-hautes performances (BFUP) classique, en utilisant des matériaux disponibles localement. Il réduit les émissions de CO[indice inférieur 2] associées à la production de clinkers de ciment (50% de remplacement du ciment) et utilise efficacement les ressources naturelles. De plus, la production de BEVUP permet de réduire les quantités de déchets de verre stockés ou mis en décharge qui causent des problèmes environnementaux et pourrait permettre de sauver des millions de dollars qui pourraient être dépensés dans le traitement de ces déchets. Enfin, il offre une solution alternative aux entreprises de construction dans la production de BFUP à moindre coût.
Abstract : Conventional concrete (CC) may cause numerous problems on concrete structures such as corrosion of steel reinforcement and weaknesses of concrete construction. As a result, most of structures made with CC require maintenance. Ultra-high-performance concrete (UHPC) can be designed to eliminate some of the characteristic weaknesses of CC. UHPC is defined worldwide as concrete with superior mechanical, ductility, and durability properties. Conventional UHPC includes between 800 and 1000 kg/m³ of cement particles, 25–35%wt of silica fume (SF), 0–40 wt% of quartz powder (QP), and 110–140 wt% quartz sand (QS) (the percentages are based on the total cement content of the mix by weight). UHPC contains steel fibers to improve its ductility and tension capacity. The huge amount of cement used to produce UHPC not only affects production costs and consumes natural resources, limestone, clay, coal, and electric power, but it also negatively impacts the environment through carbon dioxide (CO[subscript 2]) emissions, which can contribute to the greenhouse effect. Additionally, the particle-size distribution (PSD) of cement exhibits a gap at the micro scale that needs to be filled with more finer materials such as SF. Filling this gap solely with SF requires a high amount of SF (25% to 30% by cement weight) which is a limited resource and involves high cost. This significantly also decreases UHPC workability due to high Blaine surface area of SF. QS and QP use is also costly and consumes natural resources. As such, they are considered as impedances for wide use of UHPC in the concrete market and fail to satisfy sustainability requirements. Furthermore, based on an Environment Canada report, quartz causes immediate and long-term environmental harm because its biological effect makes it an environmental hazard. Furthermore, UHPC is generally sold on the market as a prepackaged product, which limits any design changes by the user. Moreover, it is normally transported over long distances, unlike CC components. This increases to the greenhouse-gas effect and leads to higher cost of the final product. Therefore, there is a vital need for other locally available materials with similar functions to partially or fully replace silica fume, quartz sand, or quartz powder, and thereby reduce the cement content in UHPC, while having comparable or better properties. In some countries, and Canada in particular, large quantities of glass cannot be recycled because of the high breaking potential, color mixing, or high recycling costs. Most waste glass goes into landfill sites, which is undesirable since it is not biodegradable and less environmentally friendly. In recent years, attempts have been made to use waste glass as an alternative supplementary cementitious material (ASCM) or ultra-fine aggregate in concrete, depending on its chemical composition and particle-size distribution (PSD). This thesis is based on a new type of ecological ultra-high-performance glass concrete (UHPGC) developed at the Université de Sherbrooke. The concrete’s design involved using waste glass of varying particle-size distributions obtained from cullets and optimizing the packing density of the entire material matrix. UHPGC can be designed with a reduced amount of cement (400–800 kg/m³), silica fume (SF) (50–220 kg/m³), quartz powder (QP) (0–400 kg/m³), and quartz sand (QS) (0–1200 kg/m³), while incorporating various waste-glass products: glass sand (GS) (0–1200 kg/m³) with an average mean diameter (d[subscript 50]) of 275 μm, a high amount of glass powder (GP) (200–700 kg/m³) with average diameter (d[subscript 50]) of 11 μm, a moderate content of fine glass powder (FGP) (50–200 kg/m³) with d[subscript 50] of 3.8 μm. UHPGC also contains steel fibers (to increase tensile strength and improve ductility) and superplasticizer (10–60 kg/m³) as well as having a water-to-binder ratio (w/b) as low as that of UHPC. Replacing cement and silica-fume particles with non-absorptive and smooth glass particles improves UHPGC rheology. Furthermore, using FGP as a SF replacement reduces the net total surface area of a SF and FGP blend. This decreases the net particle surface area, it reduces the water needed to lubricate particle surfaces and increases the slump flow at the same w/b. Moreover, the use of waste glass material in concrete leads to lower cumulative heat of hydration, which helps minimize potential shrinkage cracking. Depending on UHPGC composition and curing temperature, this type of concrete yields compressive strength ranging from 130 up to 230 MPa, flexural strength above 20 MPa, tensile strength above 10 MPa, and elastic modulus above 40 GPa. The mechanical performance of UHPGC is enhanced by the reactivity of the amorphous waste glass and optimization of the packing density. The waste-glass products in UHPGC have pozzolanic behavior and react with the portlandite generated by cement hydration. This, however, is not the case with quartz sand and quartz powder in conventional UHPC, which react at high temperature of 400 °C. The waste-glass addition enhances clogging of the interface between particles. Waste-glass particles have high rigidity, which increases the concrete’s elastic modulus. UHPGC also has extremely good durability. Its capillary porosity is very low, and the material is extremely resistant to chloride-ion permeability (≈ 8 coulombs). Its abrasion resistance (volume loss index) is less than 1.3. UHPGC experiences virtually no freeze–thaw deterioration, even after 1000 freeze–thaw cycles. After laboratory assessment, the developed concrete was scaled up with a pilot plane and field validation with the construction of two footbridges as a case study. The higher mechanical properties allowed for the footbridges to be designed with about sections reduced by 60% compared to normal concrete. UHPGC offers several economic and environmental advantages. It reduces the production cost of ultra-high-performance concrete (UHPC) by using locally available materials and delivers a smaller carbon footprint than conventional UHPC structures. It reduces the CO[subscript 2] emissions associated with the production of cement clinkers (50% replacement of cement) and efficiently uses natural resources. In addition, high amounts of waste glass cause environmental problems if stockpiled or sent to landfills. Moreover, the use of waste glass in UHPGC could save millions of dollars that would otherwise be spent for treatment and placing waste glass in landfills. Lastly, it provides an alternative solution to the construction companies in producing UHPC at lower cost.

У дисертації наведено обірунтування і вирішення науково технічної задачі, яка полягає у встановленні умов корозійно-втомного руйнування сталей трубопроводів у взаємозв’язку з параметрами фізико-механічного стану металу та механізму впливу робочого корозійного середовища. Експериментально встановлено, що метод внутрішнього тертя металів дає можливість якісно оцінювати ступінь деградації трубної сталі 17Г1С під час її експлуатації. Для всіх середовищ випробувань (лабораторне повітря, дистильована вода, модельний розчин водного конденсату 3%-ний водний розчин NаСl) параметри циклічної довговічності експлуатованої сталі 17Г1С є нижчими порівняно з неексплуатованою сталлю. Однак, якщо період зародження тріщини зменшується тільки на 10... 20%, то спад періоду поширення тріщини становить 17... 20%. Довговічність труб зі сталі 17Г1С з додаванням рідкоземельних металів збільшується на стадії поширення втомної тріщини за рахунок росту циклічної в’язкості руйнування порівняно зі звичайною сталлю. У дослідженнях зварних з’єднань показано, що матеріал зони термічного впливу ремонтних зразків зварних з’єднань сталі 17Г1С є більш чутливим до окрихчення порівняно з матеріалом зони термічного впливу вихідних зразків.
В диссертации приведено обоснование и решение научно-технической задачи, которая заключается в установлении критериев коррозийно-усталостного разрушения сталей трубопроводов во взаимосвязи с параметрами физико-механического состояния металла и механизма влияния рабочей коррозионной среды. Изучено влияние таких эксплуатационных факторов, как асимметрия цикла, частота нагрузки, форма цикла нагрузки, температура испытаний, толщина образцов, предыдущего пластического деформирования, наводораживания, суммарного воздействия предварительного пластического деформирования и наводораживания, а также электрохимических характеристик системы «металл -среда» на развитие коррозионно-усталостного разрушения. Установление достоверных параметров, которые его описывают в материалах нефтегазопроводов, должно происходить в условиях, максимально приближенных к эксплуатационным. Полученные в результате этого значения характеристик циклической трещиностойкости позволяют наиболее точно описывать кинетику роста усталостных трещин в материалах нефтегазопроводов. Для всех сред испытаний (лабораторный воздух, дистиллированная вода, модельный раствор водного конденсата, 3%-ный водный раствор NaCl) параметры циклической долговечности эксплуатируемой стали 17Г1С ниже по сравнению с неэксплуатируемой сталью. При этом, если период зарождения трещины уменьшается только на 10...20%, то уменьшение периода распространения трещины составляет 17... 20%. Экспериментально установлено, что метод внутреннего трения металлов позволяет качественно оценивать степень деградации трубной стали 17Г1С во время ее эксплуатации. Изучали также влияние количества добавок редкоземельных металлов на коррозионную прочность трубных сталей. Долговечность труб из стали 17Г1С с добавками редкоземельных металлов увеличивается на стадии распространения усталостной трещины за счет роста циклической вязкости разрушения Кfc по сравнению с обычной сталью. Содержание добавок редкоземельных металлов сверх оптимального является нерациональным, поскольку свойства трубной стали 17Г1С от этого практически не меняется. При исследовании сварных соединений испытывали образцы двух типов: 1-исходные образцы (сварное соединение двух неэксплуатированных труб); 2 -ремонтные образцы (сварное соединение катушки трубы запаса с эксплуатируемой трубой). Показано, что материал зоны термического влияния ремонтных образцов сварных соединений стали 17Г1С более чувствителен к охрупчиванию, чем материал зоны термического влияния исходных образцов. С использованием разных схем нагрузки и наводораживания опытных образцов установлено, что материал зоны термического влияния ремонтных образцов сварного соединения стали 17Г1С более чувствителен к водородному охрупчиванию по сравнению с материалом зоны термического влияния исходных образцов. Разработаны установки для оценки деградации трубных сталей методом внутреннего трения и изучения их циклической трещиностойкости С компьютеризованной измерительной системой, которая позволяющие контролировать процесс циклической нагрузки образца и его деформацию.
The Dissertation gives justification and solution to scientific and technical task which is in determination of pipeline steels corrosion and fatigue fracture candidness being interrelated with the parameters of physical and mechanical state of metals and mechanisms of working corrosive medium impact. It has been experimentally proved that internal fraction of metals enables to qualitatively evaluate the level of pipe steel 17Г1С degradations during its operation. For all testing environments (laboratory air, distilled water, modal solution of water, modal solution of water condensate 3% aqueous solution NaCl) the parameters of cyclic longevity of operational steel 17Г1С are lower in comparison with non-operational steel.

L'avancée de la technologie des PRF a suscité l'intérêt de l'introduction de nouvelles fibres, comme la fibre de basalte, qui a un potentiel d'offrir une solution efficace, lorsqu’utilisée dans les structures en béton, soit sur la résistance à la corrosion, la durabilité et la rentabilité. En outre, les codes et les guides disponibles, ne fournissent pas de recommandations pour l'utilisation de barres en PRFB puisque les recherches passées dans ce domaine sont limitées. Donc, des travaux de recherche sont nécessaires pour caractériser et comprendre le comportement des barres de PRFB dans les éléments en béton armé. En conséquence, les objectifs principaux sont d'évaluer les caractéristiques à court et long terme des barres de PRFB nouvellement développées, ainsi que d'évaluer les performances structurales de ces nouvelles barres comme renforcement interne dans les poutres et les dalles de pont et d'introduire ce nouveau renforcement dans les codes et les guides de dimensionnement. Les tests expérimentaux ont été faits en trois parties. La première partie porte sur le développement de trois nouvelles barres et tendons en PRFB pour déterminer leurs propriétés physiques et mécaniques. Les performances à long terme et de durabilité ont été réalisées en conditionnant les barres de PRFB dans une solution alcaline simulant les conditions humides dans le béton pour déterminer la compatibilité comme renforcement interne dans les éléments en béton. Par la suite, les propriétés ont été déterminées et comparées avec des spécimens non conditionnés (référence). La seconde partie a porté sur sept dalles de pont en béton armé grandeur réelle avec les bords restreints, simulant les tabliers de pont les plus utilisés en Amérique du Nord, pour évaluer la performance des dalles renforcées de PRFB et d'acier. Les dalles mesurent 3000 mm de long × 2500 mm de large × 200 mm d'épaisseur. Les dalles ont été testées jusqu'à la rupture sous une charge concentrée au centre de celles-ci simulant l'empreinte d'une roue d'un camion. Les capacités en poinçonnement sont prédites en utilisant les exigences réglementaires disponibles, et sont comparées aux résultats expérimentaux. La troisième partie de cette étude portait sur les essais de 14 poutres en béton de 3100 mm de long × 200 mm de large × 300 mm de profond pour examiner le comportement en flexion et les performances en service des barres de PRFB avec deux états de surfaces: fini sablé et crénelé. Les poutres ont été testées en flexion en quatre points avec une portée libre de 2700 mm jusqu'à la rupture. Les résultats sont introduits et discutés en terme : du comportement de la fissuration, des flèches, de la capacité en flexion et des modes de ruptures. De plus, le coefficient d'adhérence (kb) des barres de PRFB est déterminé et comparé avec les recommandations des codes et guides actuels. Les résultats sont introduits et discutés en terme : du comportement de la fissuration, des flèches, de la capacité en flexion et des modes de ruptures. De plus, le coefficient d'adhérence des barres de PRFB est déterminé et comparé avec les recommandations des codes et guides actuels. Les résultats de l'étude concluent sur la viables pour la production des barres de PRFB pour respecter les exigences des codes actuelles. Également, les résultats d'essai indiquent que les barres de PRFB ont de bonnes propriétés mécaniques et peuvent être placées dans la même catégorie que les barres de PRFV, soit grade III. De plus, le comportement des poutres et des dalles de pont renforcées de PRFB est similaire que pour un renforcement en PRFV et PRFC et les exigences réglementaires sont applicables pour les barres de PRFB.
Abstract: The advances in fiber-reinforced-polymer (FRP) technology have spurred interest in introducing new fibers, such as basalt FRP (BFRP), which has the potential to offer an efficient solution when implemented in concrete structure, such as corrosion resistant, durable and cost-effective. Furthermore, the available design codes and guides do not provide any recommendations for the use of BFRP bars since fundamental studies and relevant applications are still limited. Therefore, investigations are needed to characterize and understand the behavior of BFRP bars in concrete members. Consequently, the main objectives of this experimental investigation are to evaluate the short- and long-term characteristics of newly developed BFRP bars, as well as evaluate the structural performance of these new bars as internal reinforcement for concrete beams and bridge-deck slabs to introduce these new reinforcing bars to the design codes and guides. The experimental tests were completed through three parts. The first part was conducted on three newly developed BFRP bars and tendons to investigate their physical and mechanical properties. Durability and long-term performance were assessed by conditioning the BFRP bars in an alkaline solution simulating the moist concrete environment to determine their suitability as internal reinforcement for concrete elements. Thereafter, the properties were assessed and compared with the unconditioned (reference) values. The second part of this study was conducted on seven full-scale edge-restrained concrete bridge-deck slabs simulating actual slab-on-girder bridge-deck that is commonly used in North America to evaluate the performance of concrete bridge-deck slabs reinforced with BFRP and steel bars. The deck slabs measured 3000 mm long × 2500 mm wide × 200 mm deep. The slabs were tested up to failure under single concentrated load acting on the center of each slab simulating the footprint of sustained truck wheel load. The punching shear capacities were predicted using the available provisions, and compared with the experimental results. The third part of this study included testing of fourteen concrete beams of 3100 mm long × 200 mm wide × 300 mm deep to investigate the flexural behavior and serviceability performance of sand-coated and ribbed BFRP bars in concrete beams. The beams were tested under four-point bending over a clear span of 2700 mm until failure. The results are introduced and discussed in terms of cracking behavior, deflection, flexure capacity, and failure modes. In addition, the bond-dependent coefficient (kb) of the BFRP bars was determined and compared with the recommendations of the current FRP design codes and guides. The findings of this study concluded the feasibility of producing BFRP bars meet the requirements of the current FRP standards. Also, the test results revealed that the BFRP bars had good mechanical behavior and could be placed in the same category as grade II and grade III GFRP bars. Moreover, the behavior of the concrete bridge-deck slabs and beams reinforced with BFRP bars was quite similar to the counterparts reinforced with glass- and carbon-FRP bars and the available FRP provisions are applicable for BFRP bars. The beam test results yielded an average bond-dependent coefficient (kb) of 0.76±0.03 and 0.83±0.03 for the sand-coated and ribbed BFRP bars, respectively.

This diploma thesis discusses the basics of nanotechnology as a science and nanotechnology of concrete. Additionally, it describes carbon nanotubes and the possibilities of their dispersion using high shear mixing and sonication. This thesis further provides findings about ultrasonic dispersion parameters and characteristics of materials with the addition of carbon nanotubes. The experimental of part of this thesis focuses on the possibility of dispersing carbon nanotubes, deals with the issue of incorporating carbon nanotubes into the concrete matrix and describes its effects on the final properties of concrete. It has been observed to which extent the carbon nanotubes may affect selected physico-mechanical properties and durability of concrete.

Cette thèse est dédiée à la compréhension de l’impact des irradiations alpha sur la stabilité mécanique et la durabilité chimique du verre nucléaire. Des irradiations externes aux ions He et aux ions Au ont été réalisées sur le verre SON68 afin de simuler l’effet des particules alpha et des noyaux de reculs. L’effet simultané des deux types de particules a été étudiée avec des irradiations à double faisceau He+Au. Pour comprendre les mécanismes fondamentaux à l'origine des modifications des propriétés physico-chimiques, les irradiations ont également été réalisées sur un verre borosilicaté à 6 oxydes appelé ISG, sur le verre à vitre Planilux et sur la silice vitreuse Spectrosil 2000. Les résultats obtenus révèlent que les deux types d’irradiation ont un impact sur la dureté, le module d’Young réduit et la densité des verres. La structure des échantillons irradiés a été analysée par RMN, Ramanet XPS. L’effet des irradiations sur la durabilité chimique a été mesuré avec des tests de lixiviations en mode statique dans une eau ultra-pure portée à 90°C. Les solutions de lixiviations ont été prélevées à intervalles de temps réguliers puis analysées par ICP-MS. L’altération chimique des échantillons a été caractérisée par la perte de masse normalisée des éléments traceurs B, Li, Si, Mo, Cs relâchés en solution. La couche d’altération a été caractérisée par imagerie MEB et par spectroscopie EDX
Borosilicate glasses are intended to be used for the long-term confinement of high-level nuclear wastes. Alpha particles from the minor actinides induce modifications of the glass structure which could deteriorate the efficiency of the confinement. External irradiation with 1 MeV He ions and 7 MeV Au ions were performed in the SON68 glass in order to simulate effect of alpha particles and recoils nucleus. Dual beam irradiations composed by He+Au ions were also investigated in order to simulate both effects of those two kind of particles. To understand the fundamental origin in physico-chemical properties, irradiation were also carried out on a 6 oxides borosilicate glass called International Simplified Glass (ISG) and two commercially available glass Planilux and Spectrosil 2000, both from Saint-Gobain. The mechanical properties and chemical durability of each glass were studied as a function of the cumulated dose. Results show that both alpha particles and heavy ions lead to variation in hardness, reduced Young’s modulus and density. Characterization techniques such as Raman, RMN, and XPS spectroscopy were used to analyze structural modifications induced by radiations. Chemical durability of pristine and irradiated glasses was determined by monitoring the release of glass alteration elements B, Li, Si, Mo and Cs. The alteration layer was characterized by SEM imaging and EDX spectroscopy

A realização de uma eficiente gestão e gerenciamento dos resíduos sólidos urbanos (RSU) é um desafio ao meio técnico-acadêmico e administrativo das grandes cidades. Os resíduos de construção e demolição (RCD) consistem em uma importante parcela dos RSU, em função do volume dos mesmos se é gerado e dos danos que estes podem trazer ao meio-ambiente. A reciclagem dos RCD tem sido uma solução adotada no gerenciamento dos mesmos, sendo em sua grande maioria voltada para a produção de agregados reciclados, em função do grande volume de agregados que são usados pela indústria da construção civil. Entretanto, a grande variabilidade apresentada na composição desses agregados é uma das barreiras na difusão do uso dos mesmos como matéria-prima alternativa na confecção de concretos. Com o intuito de contribuir nesta área de conhecimento, através dos resultados obtidos em um programa experimental baseado em um projeto fatorial fracionado composto de segunda ordem, que contempla a produção de concretos com os três principais componentes do RCD (concreto, argamassa e cerâmica vermelha), modelou-se o comportamento da resistência à compressão (fc), do módulo de deformação (Ec), da retração por secagem (\'épsilon\') e do volume de poros permeáveis (VPP) dos concretos produzidos, ao se variar o teor de substituição dos agregados naturais pelos reciclados e a relação água/cimento. Os resultados indicam que com exceção da resistência à compressão para o concreto confeccionado com o agregado miúdo reciclado de cerâmica vermelha, a substituição dos agregados naturais pelos reciclados minora o desempenho dos concretos para todas as propriedades estudadas. Observou-se também que a substituição do agregado miúdo natural pelos miúdos reciclados influencia mais no desempenho dos concretos, sobre as propriedades estudadas, que a substituição dos agregados graúdos naturais pelos graúdos reciclados. Ao se validar os modelos propostos para a fc e para o Ec, utilizando dados provenientes de outros autores, observou-se que tais modelos descrevem muito bem o comportamento das propriedades, embora não tenham produzido valores semelhantes aos publicados originalmente. Simulou-se também, utilizando os modelos propostos, o uso dos agregados reciclados de RCD de algumas cidades brasileiras na fabricação de concretos, sendo que, de uma maneira geral, percebeu-se uma grande viabilidade no uso dos mesmos, uma vez que os concretos simulados ainda atingiram consideráveis fc e Ec, principalmente quando se utilizou o agregado miúdo. Classificaram-se também os concretos quanto à durabilidade baseando-se nos acréscimos do VPP para com o concreto de referência de relação a/c=0,46, sendo que a classificação encontrada sugere que os concretos com elevados teores de substituição não possuem um bom desempenho com relação à sua durabilidade, sendo a substituição de pequenos teores dos agregados miúdos mais recomendada. De uma maneira geral, pode-se concluir que é possível utilizar agregados reciclados, considerando-se as variabilidades dos mesmos, na produção de concretos com desempenho mecânico e durabilidade satisfatórios, dentro das condições estudadas.
An efficient solid waste management is a challenge to the technician-academic and administrative sectors of great cities. Construction and demolition (C&D) wastes are an important portion of solid wastes, due to their great volume and to the damages that they can bring to the environment. Recycle C&D wastes has been adopted as a management solution and the production of recycled aggregates has been a practice quite used, in function of the great volume of aggregates that have been used by the construction industry. However, the great variability presented in the composition of those aggregates is one barrier to diffuse the use of them as an alternative material to make concrete. Intending to contribute in this knowledge area, an experimental program based on a fractional factorial project was done. It consisted in produce concretes with the three main components of C&D waste (concrete, mortar and red ceramic) as recycled aggregates, varying the percentage of substitution of natural aggregates by recycled aggregates and the water/cement ratio. Strength (fc), modulus of elasticity (Ec), shrinkage (épsilon\') and volume of permeable voids (VPP) of concretes were measured and the results were modeled using statistical tools. The results indicated that except the fc for concrete made with recycled red ceramic fine aggregate, the recycled aggregates lessens the concrete\'s behavior for all studied properties. It was also observed that the natural fine aggregate\'s substitution by recycled fine aggregates influences less in the concrete\'s behavior than the coarse aggregate\'s substitution, for all studied properties. To validate the proposed models, using other authors\' data, it was observed that such models describe the properties behavior very well, although such models don\'t produce properties values similar to the values published by the authors. It was also simulated, through the proposed models, the use of the recycled aggregates of C&D waste from some brazilian cities in concrete production and, in a general way, it was noticed a great viability in the use of the same ones, once the simulated concretes still reached considerable fc and Ec, mainly when the recycled fine aggregates was used. The recycled concrete\'s durability was also determined using the VPP increments in relation to a 0.46 water/cement ratio reference concrete. This classification suggests that the concretes with high tenors of substitution don\'t have a good behavior, being small tenors of substitution of fine aggregates more recommended. In general, it can be concluded that it is possible to use recycled aggregates, considering their variability, to produce concretes with satisfactory mechanical behavior and durability, considering the studied conditions.