In recent years supramolecular chemistry has established as one of the most active fields of science. The most significant feature of supramolecular chemistry is the use of building blocks which reversibly held together by intermolecular forces, electrostatic or H-bonding. Therefore, the synthesis of supramolecular systems using different non-covalent assemblies provides some unique architectures and features which are extremely difficult to be obtained via covalent synthesis. One main application of such influencing supramolecular systems is the preparation of self-healing materials. Among various approaches to self-healing effects, reversible bond formation has become prominent in the last years. To achieve both acceptable mechanical performance and self-healing behaviour from a polymeric material, proper balance between covalent and non-covalent bonding is important. The covalent bonding gives a basic strength to the material while the non-covalent bonding generates self-healing effects in the case of damage. The main aim of this study was to synthesize an organic moiety which is capable of forming supramolecular assemblies in the presence of suitable counterparts, followed by its incorporation on to polymer matrix and investigation of the final properties. For reversible bond forming technique H-bonding is exploited in this work. 4-substituted-2,6-diaminopyridine is selected as the organic moiety as it has a clear DAD (donor-acceptor-donor) structure and thus able to undergo self-association or triple hydrogen bonded complex formation with respective counterparts. Chichibabin reaction was utilised for the synthesis and 4-hydroxy-2,6-diamido pyridine was synthesised as the key compound. Initially different derivatives of 4-hydroxy-2,6 diamino pyridine was synthesized and utilised towards the formation of supramolecular network with a suitable monomeric counterpart. Poly (butadiene-co-maleic anhydride) is used as the base polymer as it has the possibility to introduce non-covalent bonding sites through grafting reactions on the double bonds or on maleic anhydride groups. The free amine group present in the main compound was grafted onto the backbone of poly (butadiene-co-maleic anhydride) via reaction of amine with maleic anhydride group. The main design of supramolecular self-assembly within poly (butadiene-co-maleic anhydride) with a suitable counterpart poly (butadiene-co-maleimide), is prepared and used in this thesis. The miscibility of the two polymers is proven by the presence of a single Tg in the DSC results of the mixture and also by the formation of homogeneous films with no phase separation in AFM. However the formation of hydrogen bonding within the monomer was proven by 1H NMR, IR studies. Further formation of complex between two polymers was established from the results of viscosity. Also the interactions between the complexes exert a distinct influence on the rheological behavior of the blend. Lastly the reversibility of this supramolecular blend was assured by temperature dependent viscosity values. In the final part of this work, bromobutyl rubber (BIIR) is selected as the model elastomer which has vast application in the tire industry; as the inner-liner that holds the air in the tire and also used as rubber stoppers for sealing medicine vials and bottles The bromine functionality can be substituted with an amine group making it more susceptible towards the incorporation of different organic moieties. In this way, the derivative of 2,6-diaminopyridine having a pendant amine group is incorporated in BIIR. As a counterpart uracil is used as its H-bond forming ability with diaminopyridine moieties is well established and supported by different previous research works. The supramolecular network formed between these two monomers help to generate self-healing effects within BIIR rubber. Fig. 2 represents the supramolecular network formed between chains of BIIR. The self-healing effect of the rubber material is examined through the stress-strain experiments where up to 82% healing was observed when heated up to 70 °C. With increasing temperature better healing was observed whereas at room temperature a 40% healing tendency was noticed. It is also interesting to note that the thermal and dynamic mechanical properties of this tailor made self-healing BIIR is identical with sulphur cured conventional BIIR.

Τα δομικά πολυμερή είναι ευαίσθητα σε βλάβες με τη μορφή των ρωγμών, οι οποίες σχηματίζονται βαθιά μέσα στη δομή τους, όπου η ανίχνευση είναι δύσκολη και η επισκευή είναι σχεδόν αδύνατη. Το σπάσιμο οδηγεί σε μηχανική υποβάθμιση των ενισχυμένων με ίνες πολυμερικών σύνθετων υλικών. Στα μικρο-ηλεκτρονικά πολυμερή μπορεί επίσης να οδηγήσει σε ηλεκτρολογική βλάβη. Η ζημία εμφανίζεται σχεδόν σε κάθε σύνθετο υλικό σε μορφή μικρο-ρωγμών που αναπτύσσονται στη εποξειδική μήτρα η οποία δεσμεύει τις ίνες μαζί. Οι μικρο-ρωγμές προκαλούνται από τη θερμική και μηχανική καταπόνηση και είναι ένα μακροχρόνιο πρόβλημα στα εποξειδικά πολυμερή. Ένα in-situ σύστημα αυτόνομης ίασης, με ενσωματωμένες μικρο-κάψουλες και έναν καταλύτη ώστε να προκαλέσει μια αντίδραση μεταθέσεως με άνοιγμα δακτυλίου (ROMP), μπορεί να χρησιμοποιηθεί σε μια προσπάθεια να δεσμεύσει ξανά τις μικρο-ρωγμές. Ανεξάρτητα από την εφαρμογή, αφού έχουν σχηματιστεί ρωγμές εντός πολυμερικών υλικών, η ακεραιότητα της δομής τους είναι σημαντικά μειωμένη. Σε αυτή τη διατριβή γίνεται μελέτη για τη θεραπεία των ζημιών λόγο αποκόλλησης σε εποξειδικά σύνθετα υλικά ενισχυμένα με υφάσματα ινών. Μελετώνται δύο τύποι διαδικασίας επούλωσης. Στον πρώτο, ένα καταλυμένο μονομερές χειροκίνητα εγχέεται στην περιοχή θραύσης λόγω αποφλοίωσης. Στον δεύτερο, περιγράφεται ένα πλήρως ολοκληρωμένο in situ σύστημα με ενσωματωμένες μικρο-κάψουλες και τον καταλύτη τους. Για το πρώτο σύστημα, ελέγχθηκαν δείγματα δοκού διπλής άρθρωσης (DCB) για να μελετηθεί η επούλωση της αποελασματοποίησης σε σύνθετα συγκρίνοντας την ανθεκτικότητα του παρθένου δείγματος με τη σκληρότητα του ίδιου δείγματος μετά την πλήρης επούλωση. Ηλεκτρονική μικροσκοπία σάρωσης (SEM) και Φασματοσκοπία Raman χρησιμοποιούνται για την ανάλυση των επιφανειών θραύσης, ώστε να παρουσιαστούν τα φυσικά στοιχεία της επισκευής. Στη συνέχεια, περιγράφεται η ανάπτυξη ενός πολυμερικής μήτρας σύνθετου υλικού που έχει την ικανότητα να θεραπεύει ρωγμές αυτόματα. Το σύστημα χρησιμοποιεί έναν παράγοντα επισκευής μονομερούς, δικυκλοπενταδιένιο (DCPD), το οποίο είναι αποθηκευμένο σε μικρο-κάψουλες οι οποίες περιέχουν τον υγρό παράγοντα επισκευής, διεσπαρμένες στην εποξειδική μήτρα. Όταν το υλικό έχει υποστεί βλάβη, ρωγμές διαδίδονται μέσω του υλικού σπάζοντας τις μικρο-κάψουλες, απελευθερώνοντας τον παράγοντα επισκευής εντός του επιπέδου της ρωγμής. Τέλος, ο παράγοντας DCPD επισκευής στερεοποιείται με πολυμερισμό μεταθέσεως με άνοιγμα δακτυλίου (ROMP) όταν έρχεται σε επαφή με ένα, με βάση το ρουθήνιο, καταλύτη (Grubbs), ο οποίος διασπείρεται και αυτός εντός της μήτρας. Η διαδικασία με την οποία παρασκευάζονται οι μικρο-κάψουλες γεμάτες με DCPD και οι διάφορες τεχνικές όπως οπτική μικροσκοπία, ηλεκτρονική μικροσκοπία σάρωσης (SEM), διαφορική θερμιδομετρία σάρωσης (DSC), θερμική βαρυμετρική ανάλυση (TGA) και δυναμική μηχανική ανάλυση (DMA) που χρησιμοποιήθηκαν για το χαρακτηρισμό των μικρο-κάψουλων συζητούνται σε αυτήν την εργασία. / Structural polymers are susceptible to damage in the form of cracks, which form deep within the structure where detection is difficult and repair is almost impossible. Cracking leads to mechanical degradation of fibre-reinforced polymer composites; in microelectronic polymeric components it can also lead to electrical failure. Damage occurs in almost every composite material in the form of microcracks that develop in the epoxy matrix that binds the fibers together. Microcracking induced by thermal and mechanical fatigue is also a long-standing problem in polymer adhesives. An in-situ self-healing system uses embedded microcapsules and a catalyst that trigger a romp reaction in an effort to rebond the microcracks. Regardless of the application, once cracks have formed within polymeric materials, the integrity of the structure is significantly compromised. A study of the healing of delamination damage in woven reinforced epoxy composites is performed in this thesis. Two types of healing process are studied. In the first, a catalyzed monomer is manually injected into the delamination. In the second, a fully integrated in situ system is described with embedded microcapsules and catalyst. Double-cantilever-beam (DCB) specimens were tested to study the healing of delamination in composites by comparing the toughness of the virgin specimen with the toughness of the same specimen after healing was complete. Scanning electron microscopy (SEM) and Raman Spectroscopy are used to analyze the fracture surfaces and provide physical evidence of repair. The development of a self-healing polymer-matrix composite material that possesses the ability to heal cracks autonomically is described. The system uses a monomer repair agent, dicyclopentadiene (DCPD), which is stored in an epoxy matrix by dispersing microcapsules containing the liquid repair agent throughout the matrix. When the material is damaged, cracks propagate through the material and break open the microcapsules, releasing the repair agent into the crack plane. Finally, the DCPD repair agent solidifies by ring-opening metathesis polymerization (ROMP) after coming in contact with a ruthenium-based catalyst (Grubbs' catalyst) dispersed in the matrix. The process by which the DCPD-filled microcapsules are prepared and the various techniques such as optical microscopy, scanning electron microscopy (SEM), differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA) and dynamic mechanical analysis (DMA) to characterize the microcapsules are discussed in this work.

<p>Extending the functional lifetime of acrylic poly(methyl methacrylate) (PMMA) bone cement may reduce the number of revision total joint replacement (TJR) surgeries performed each year. We developed a system utilizing an encapsulated water-reactive, FDA-approved tissue adhesive, 2-octyl cyanoacrylate (OCA), as a healing agent to repair microcracks within a bone cement matrix. The proposed research tested the following hypotheses: (1) reactive OCA can be successfully encapsulated and the resulting capsules thoroughly characterized; (2) the static mechanical properties of the PMMA composite can be improved or maintained through inclusion of an optimal wt% of OCA-containing capsules; (3) PMMA containing encapsulated OCA has a prolonged lifetime when compared with a capsule-free PMMA control as measured by the number of cycles to failure; and (4) the addition of capsules to the PMMA does not significantly alter the biocompatibility of the material. Based on the experiments reported herein, the primary conclusions of this dissertation are as follows: (1) functional OCA can be encapsulated within polyurethane spheres and successfully incorporated into PMMA bone cement; (2) lower wt% of capsules maintained the tensile, compressive, fracture toughness, and bending properties of the PMMA; (3) inclusion of 5 wt% of OCA-containing capsules in the matrix increased the number of cycles to failure when compared to unfilled specimens and those filled with OCA-free capsules; and (4) MG63 human osteosarcoma cell proliferation and viability were unchanged following exposure to OCA-containing PMMA when compared with a capsule-free control.</p> / Dissertation

Recently, interest in Smart Grid (SG) as a tool for modernization and automation of the current distribution system has rapidly increased. This interest can be explained by the common belief that SG technologies greatly enhance system reliability, power quality and overall efficiency. One of the most important objectives of an SG is to accommodate a wide variety of generation options. This objective aligns with the new trends and policies that encourage higher penetration levels of Distributed Generation (DG) according to environmental, regulatory and economical concerns. Most DG units are either renewable or low emission energy sources, thus meeting the Canadian emission portfolios, while they remain attractive for both utilities and customers for different reasons. DG units can postpone large investment in transmission and central generation, reduce energy losses, and increase system reliability and power quality. SG is centered on several objectives such as self-healing, motivating consumers to participate in grid operation, resisting attacks, accommodating a wide variety of DG units and storage devices, and optimizing assets. Yet, one of the main goals of SG is to increase the reliability of power systems. Reliability is a vital factor in power system performance, due to the full dependence of today???s life on electricity and the high cost of system outages, especially for critical loads. Therefore, one of the main salient features of SG is its ability of self-healing. The insertion of DG units changes distribution networks from being passive with unidirectional power flow and a single power source (the primary substation) towards active networks with multi-directional power flow and several power sources (the primary substation, along with DG units). As a result, the interconnection of DG units creates several impacts on different practices such as voltage profile, power flow, power quality, stability, reliability, fault detection, and restoration. Current policies call for the direct disconnection of all DG units once any failure occurs in the network. However, with a high DG power penetration, the utilities cannot operate the system efficiently without the DG units??? support. Furthermore, automatic disconnection of the DG units during faults reduces the expected benefits associated with DG units drastically. Motivated by the above facts, the overall target of this thesis is to introduce distribution system mechanisms to facilitate realizing the concept of Smart Distribution System (SDS) in both normal and emergency modes. In particular, three main functions are dealt with in this research work: distribution network reconfiguration, DG allocation and self-healing. First, for distribution network reconfiguration, a method based on genetic algorithm is presented to address the reconfiguration problem for distribution systems while the effect of load variation and the stochastic power generation of renewable-based DG units are taken into consideration. The presented method determines the annual distribution network reconfiguration scheme considering switching operation costs in order to minimize annual energy losses by determining the optimal configuration for each season of the year. Second, for DG allocation, a joint optimization algorithm has been proposed to tackle the DG allocation and network reconfiguration problems concurrently, as these two issues are inherently coupled. The two problems are dealt with together while the objectives are minimizing the cost, as an economic issue, and greenhouse gas emissions, as an environmental issue. The proposed method takes the probabilistic nature of both the renewable energy resources and loads into account. The last operation function dealt with in this thesis is distribution system restoration. In order to accomplish this function, two stages are presented: In the first stage, numerous practical aspects related to service restoration problem have been investigated. These aspects include variations in the load and customer priorities, price discounts for in-service customers based on their participation in a load-curtailment scheme that permits other customers to be supplied, the presence of manual and automated switches, and the incorporation of DG units (dispatchable and wind-based units) in the restoration process. In the second stage, the smart grid concept and technologies have been applied to construct a self-healing framework to be applied in smart distribution systems. The proposed multi-agent system is designed to automatically locate and isolate faults, and then decide and implement the switching operations to restore the out-of-service loads. Load variation has been taken into consideration to avoid the need for further reconfigurations during the restoration period. An expert-based decision-making algorithm has been used to govern the control agents. The rules have been extracted from the practical issues related to the service restoration problem, discussed in the first stage.

Apesar dos avanços tecnológicos e do conhecimento disponível sobre o concreto e suas propriedades, muitas estruturas apresentam-se degradadas prematuramente. Assim, são necessárias frequentes intervenções para reparo havendo, em consequência, consumo de quantidades expressivas de materiais, com importantes impactos financeiros e ambientais. A preocupação crescente com o desempenho das estruturas de concreto tem incentivado vários segmentos da sociedade a buscarem soluções que assegurem sua durabilidade. Nesse sentido, muitas pesquisas acadêmicas vêm sendo desenvolvidas para melhor entender o comportamento do concreto frente a diferentes condições de uso, considerando-se suas propriedades mecânicas e de durabilidade. Esta pesquisa teve por objetivo analisar o desempenho de concretos frente à retração por secagem, após terem sido submetidos ao pré-carregamento. Foram utilizados os cimentos CP V ARI e CP IV, nas relações a/c 0,35, 0,50 e 0,70, e adotadas as idades de cura de 7 e 28 dias. Nas idades 1, 3 e 7 dias, os concretos foram submetidos a carregamentos de 25%, 50% e 75% da carga média de ruptura à tração na flexão (NBR 12142, ABNT, 2010). Realizou-se o ensaio para determinação da retração por secagem (ASTM C157/C157M-08, 2014e1), em concretos de referência e nos pré-carregados. Foram também realizadas análises complementares, como determinação da velocidade da onda ultrassônica (NBR 8802, ABNT, 2013), porosimetria por intrusão de mercúrio e microtomografia de raios X. Comparando-se o desempenho dos concretos pré-carregados ao dos concretos de referência, o cimento CP V ARI apresentou redução da retração média, exceto para a relação a/c 0,35 com cura de 7 dias. Nos concretos com cimento CP IV, a retração média diminuiu para a relação a/c 0,70, com ambas as idades de cura. O pré-carregamento provocou, em maior ou menor grau, a associação de dois diferentes efeitos. Por um lado, a compactação ocasionou a quebra dos compostos menos resistentes da matriz, havendo um efeito físico de redução dos vazios capilares, além da exposição de grãos anidros. Em paralelo, ocorreu a microfissuração do concreto, favorecendo, também, a exposição de grãos anidros. A cura por imersão possibilitou a continuidade da hidratação, com a formação de novos produtos resistentes na matriz, reduzindo as porosidades total e efetiva e, portanto, a taxa da retração do concreto. Além da densificação da matriz, a cura prolongada possibilitou a hidratação dos grãos anidros de cimento expostos nas paredes das microfissuras, favorecendo a sua autocicatrização (self-healing), o que contribuiu com a recuperação da capacidade resistente dos concretos, frente aos esforços da secagem. Assim, a associação destes fatores promoveu a redução da retração por secagem nos concretos estudados, principalmente nos mais porosos. / The growing concern with the performance of structures has encouraged several segments of society to find solutions to improve concrete durability. Several studies have been made to provide a better understanding of the mechanical properties and concrete durability in different conditions. This study assessed the drying shrinkage performance of preloaded concrete. Cement types CP V ARI, equivalent to Portland type III (ASTM C150/C150M-16e1) and CP IV, equivalent to Portland type IP (ASTM C595/C595M-16) were used with w/b = 0.35, 0.50 and 0.70 and curing ages of 7 and 28 days. At the ages of 1, 3 and 7 days, concrete mixes were subject to loads of 25%, 50% and 75% of their mean ultimate flexural strength (Brazilian Standard NBR 12142, ABNT, 2010). Drying shrinkage in reference and preloaded concrete was determined according to ASTM C157/C157M-14e1. Additional tests included ultrasound pulse velocity (NBR 8802, ABNT, 2013), mercury intrusion porosimetry (MIP) and X-ray microtomography. Preloaded CP V ARI cement concrete showed a drop in mean shrinkage when compared with the reference mix, except for the mix with w/b = 0.35 cured for 7 days. For CP IV cement, mean shrinkage dropped with w/b =0.70 for both curing ages. Early loading caused a compaction effect, promoting the weakest compounds of the matrix to be broken, filling the capillary voids. In this process some unhydrous grains probably were exposed. On the other hand, microcracking also occurred, lefting unhydrated grains exposed in the microcracks walls. Due to immersion curing, the availability of water promoted the hydration continuity. New resistant hydrates filled the large voids and reduced the total and effective porosities in the cement matrix. The hydration of anhydrous grains in the microcracks walls had led to self-healing, with partial resistance capacity recovery. The combined effect of these factors promoted the drying shrinkage reducing, mainly for the more porous concrets.

Dans le cadre de la fabrication de pièces structurales pour l’industrie aéronautique, de nouveaux matériaux composites à matrice céramique sont envisagés par le motoriste Safran. Lors de l’utilisation dans des environnements sévères de combustion, et sous chargement mécanique, la matrice pourra s’endommager par fissuration et la capacité du matériau à s’auto-protéger sera réduite. Les travaux présentés dans cette thèse ont pour but d'identifier les mécanismes prépondérants de ruine de ce type de matériaux composites en fonction de différentes sollicitations thermiques, mécaniques et environnementales. Une démarche multi-échelle a été adoptée, de manière à considérer les phénomènes à une échelle microscopique (chaque constituant) et macroscopique (synergie entre les constituants au sein du matériau). Le comportement en oxydation/corrosion du matériau composite et de chacun de ses constituants a été caractérisé puis modélisé pour être extrapolé à des environnements de combustion. Différents domaines de protection du matériau ont ainsi été mis en évidence. Dans cette même optique, le comportement thermomécanique des constituants matriciels et du composite a fait l’objet d’essais de fluage pour déterminer les paramètres d’une première modélisation, et analyser les dégradations associées. En couplant les différents résultats obtenus, il est ainsi possible d’évaluer la criticité des différents phénomènes de ruine. Des scenarii de ruine sont donc présentés. / To design and manufacture CMC structural components for aeronautics, Safran develops a new CMC grade, provided to resist severe combustion environments. Understanding this new composite material damaging and failure mechanisms is essential: environmental conditions, mechanical loading, and matrix damages, can lead to a decrease in its self-protective properties. The aim of this work is to identify prevailing high temperature degradation mechanisms of those MI SiC/SiC CMCs, depending of different thermal, mechanical and environmental stresses. To fulfill that outcome, a multi-scale approach was considered, by examining phenomena from single constituents to complex composite architecture (effects of constituents’ synergy). High temperature oxidation/corrosion behaviors of the composite material and each of its constituents were characterized, and modeled to meet representative combustion environment. Different operating areas of efficient self-protection of the composite material were therefore highlighted. In the same perspective, themomechanical behaviors of both matrix constituents and composite were experimentally explored, enabling the determination of behavior laws. Related degradations in the composite material were also analyzed. Crossing all results, it was thereby possible to evaluate kinetics and criticality of failure mechanisms: different damaging scenarios are thus proposed, depending on environmental conditions.

Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2018-02-15T13:47:25Z No. of bitstreams: 1 JonathaRevoredoLeiteDaFonseca_DISSERT.pdf: 6647169 bytes, checksum: 89682e384a5fef047471acede0d629b4 (MD5) / Approved for entry into archive by Arlan Eloi Leite Silva (eloihistoriador@yahoo.com.br) on 2018-02-20T21:24:35Z (GMT) No. of bitstreams: 1 JonathaRevoredoLeiteDaFonseca_DISSERT.pdf: 6647169 bytes, checksum: 89682e384a5fef047471acede0d629b4 (MD5) / Made available in DSpace on 2018-02-20T21:24:35Z (GMT). No. of bitstreams: 1 JonathaRevoredoLeiteDaFonseca_DISSERT.pdf: 6647169 bytes, checksum: 89682e384a5fef047471acede0d629b4 (MD5) Previous issue date: 2017-07-06 / Este trabalho tem como objetivo propor uma Smart Grid composta por duas subesta??es para a implanta??o da t?cnica de self healing utilizando o Simulador Digital em Tempo Real (RTDS ? Real Time Digital Simulator) e rel?s de prote??o IEDs (Intelligent Electronic Devices) com comunica??o atrav?s da padr?o IEC 61850 entre eles. Nas redes el?tricas de distribui??o, t?cnicas de recomposi??o autom?tica (self healing) podem ser usadas com o intuito de diminuir os tempos com a perda do fornecimento de energia el?trica aos consumidores ocasionado por curto-circuito, diminuindo assim os preju?zos aos consumidores e em decorr?ncia de multas. A metodologia aplicada ? baseada na modelagem do circuito proposto no RTDS, que ? monitorado em tempo real. S?o simulados v?rios tipos de curtos-circuitos em diferentes pontos do sistema e, na ocorr?ncia de cada falta gerada, o programa desenvolvido analisa os dados do sistema pr? e p?s falta, isolando o trecho do circuito afetado e ir? reconfigurar automaticamente a rede de forma a restabelecer o fornecimento de energia para as cargas afetadas. A escolha do arranjo final da rede, ap?s o processo de reconfigura??o autom?tica, ser? baseada em um processo de otimiza??o intitulado Reconfigura??o por Soma de Pot?ncias ? RSP. A comunica??o entre o RTDS e os IEDs (que fazem a prote??o de parte do sistema) utiliza o padr?o IEC 61850 com troca de mensagens GOOSE (Generic Object Oriented Substation Event) aplicando os aspectos relevantes desse padr?o. / This work aims to propose a Smart Grid composed of two substations for the implementation of the self healing technique using Real Time Digital Simulator (RTDS) and IED (Intelligent Electronic Devices) protection relays with communication through standard IEC 61850 between them. In distribution networks, self healing techniques can be used in order to reduce the times with the loss of electricity supply to consumers caused by a short circuit, thus reducing the losses to consumers and due to fines. The methodology applied is based on the proposed circuit modeling in the RTDS, which is monitored in real time. Several types of short circuits are simulated at different points in the system and, in each fault generated, the program developed analyze the pre and post fault system data, isolating the section affected and automatically reconfiguring the circuit to restore the power supply to the affected loads. The choice of the final network arrangement, after the automatic reconfiguration process, is based on an optimization process called Reconfiguration by Power Addition - RPA .Communication between RTDS and IEDs (which protect part of the system) use the IEC 61850 standard with GOOSE (Generic Object Oriented Substation Event) message exchange applying the relevant aspects of this standard.

Apesar dos avanços tecnológicos e do conhecimento disponível sobre o concreto e suas propriedades, muitas estruturas apresentam-se degradadas prematuramente. Assim, são necessárias frequentes intervenções para reparo havendo, em consequência, consumo de quantidades expressivas de materiais, com importantes impactos financeiros e ambientais. A preocupação crescente com o desempenho das estruturas de concreto tem incentivado vários segmentos da sociedade a buscarem soluções que assegurem sua durabilidade. Nesse sentido, muitas pesquisas acadêmicas vêm sendo desenvolvidas para melhor entender o comportamento do concreto frente a diferentes condições de uso, considerando-se suas propriedades mecânicas e de durabilidade. Esta pesquisa teve por objetivo analisar o desempenho de concretos frente à retração por secagem, após terem sido submetidos ao pré-carregamento. Foram utilizados os cimentos CP V ARI e CP IV, nas relações a/c 0,35, 0,50 e 0,70, e adotadas as idades de cura de 7 e 28 dias. Nas idades 1, 3 e 7 dias, os concretos foram submetidos a carregamentos de 25%, 50% e 75% da carga média de ruptura à tração na flexão (NBR 12142, ABNT, 2010). Realizou-se o ensaio para determinação da retração por secagem (ASTM C157/C157M-08, 2014e1), em concretos de referência e nos pré-carregados. Foram também realizadas análises complementares, como determinação da velocidade da onda ultrassônica (NBR 8802, ABNT, 2013), porosimetria por intrusão de mercúrio e microtomografia de raios X. Comparando-se o desempenho dos concretos pré-carregados ao dos concretos de referência, o cimento CP V ARI apresentou redução da retração média, exceto para a relação a/c 0,35 com cura de 7 dias. Nos concretos com cimento CP IV, a retração média diminuiu para a relação a/c 0,70, com ambas as idades de cura. O pré-carregamento provocou, em maior ou menor grau, a associação de dois diferentes efeitos. Por um lado, a compactação ocasionou a quebra dos compostos menos resistentes da matriz, havendo um efeito físico de redução dos vazios capilares, além da exposição de grãos anidros. Em paralelo, ocorreu a microfissuração do concreto, favorecendo, também, a exposição de grãos anidros. A cura por imersão possibilitou a continuidade da hidratação, com a formação de novos produtos resistentes na matriz, reduzindo as porosidades total e efetiva e, portanto, a taxa da retração do concreto. Além da densificação da matriz, a cura prolongada possibilitou a hidratação dos grãos anidros de cimento expostos nas paredes das microfissuras, favorecendo a sua autocicatrização (self-healing), o que contribuiu com a recuperação da capacidade resistente dos concretos, frente aos esforços da secagem. Assim, a associação destes fatores promoveu a redução da retração por secagem nos concretos estudados, principalmente nos mais porosos. / The growing concern with the performance of structures has encouraged several segments of society to find solutions to improve concrete durability. Several studies have been made to provide a better understanding of the mechanical properties and concrete durability in different conditions. This study assessed the drying shrinkage performance of preloaded concrete. Cement types CP V ARI, equivalent to Portland type III (ASTM C150/C150M-16e1) and CP IV, equivalent to Portland type IP (ASTM C595/C595M-16) were used with w/b = 0.35, 0.50 and 0.70 and curing ages of 7 and 28 days. At the ages of 1, 3 and 7 days, concrete mixes were subject to loads of 25%, 50% and 75% of their mean ultimate flexural strength (Brazilian Standard NBR 12142, ABNT, 2010). Drying shrinkage in reference and preloaded concrete was determined according to ASTM C157/C157M-14e1. Additional tests included ultrasound pulse velocity (NBR 8802, ABNT, 2013), mercury intrusion porosimetry (MIP) and X-ray microtomography. Preloaded CP V ARI cement concrete showed a drop in mean shrinkage when compared with the reference mix, except for the mix with w/b = 0.35 cured for 7 days. For CP IV cement, mean shrinkage dropped with w/b =0.70 for both curing ages. Early loading caused a compaction effect, promoting the weakest compounds of the matrix to be broken, filling the capillary voids. In this process some unhydrous grains probably were exposed. On the other hand, microcracking also occurred, lefting unhydrated grains exposed in the microcracks walls. Due to immersion curing, the availability of water promoted the hydration continuity. New resistant hydrates filled the large voids and reduced the total and effective porosities in the cement matrix. The hydration of anhydrous grains in the microcracks walls had led to self-healing, with partial resistance capacity recovery. The combined effect of these factors promoted the drying shrinkage reducing, mainly for the more porous concrets.

It is well-known that concrete permeability is a good indicator of its expected durability until it remains uncracked. However, in various stages of its service life, different types of cracking in concrete can be developed due to exposure to different deterioration processes such as early plastic shrinkage or chloride-induced reinforcement corrosion. Although these cracks may not endanger concrete’s structural performance from the mechanical point of view, they create a pathway for aggressive ions that can initiate degradation processes, lead to increase in concrete permeability and thus reduce its durability. Cracking in concrete might not be preventable, but its capability to naturally seal small cracks, named autogenous self-healing (SH), provides an additional feature to manufacture more durable concrete structures. However, natural self-healing capability of concrete is limited and therefore it is typically omitted in the design of concrete structures. Hence, more attention has been recently paid to Engineered Self-healing Concrete (EShC) which is associated with artificially triggered healing mechanisms into the cementitious matrix by incorporating various substances such as crystalline products. EShC helps in reducing concrete permeability; thus, increasing its service-life and durability. Due to formation of needle-shaped pore-blocking crystals, Crystalline Admixtures (CA), as a candidate from the Permeability-Reducing Admixtures (PRA) category, can be implemented into concrete mixtures to fabricate EShC concretes. Crystalline waterproofing technology is not new, but still is unknown to many researchers, engineers, and construction industry professionals. The lack of knowledge of its microstructure and self-healing properties limits CA’s proper usage in the construction industry. The techniques to assess the self-healing capability of mortar and concrete are not well-standardized yet. No research work has been done to address certain durability characteristics of this material (i.e. electrical resistivity (ER) or chloride diffusivity) especially when combined with Supplementary Cementitious Materials (SCM) and Portland Limestone Cement (PLC). Since the resistance of concrete against ions’ penetration is a function of its permeability, it might be a straightforward and reliable parameter to rapidly evaluate concrete’s durability during its intended service life. Hence, electrical resistivity measurement is considered as an indirect and alternative tool for other time-consuming permeability testing techniques to examine the CA’s efficiency as it modifies the concrete’s microstructure by crystals’ deposition; thus, leads to permeability improvement. In comparison to previous studies, on a larger scale, this thesis aims to systematically study the effects of CA on the microstructural features, self-healing properties and long-term durability and resistivity of cement-based materials and in addition, draw some comprehensive conclusions on the use of CA in new and repair applications. This study is divided into three major phases to propose all-inclusive work on using CA in construction industry. To satisfy the goals of each individual phase, a test matrix consisting of a series of four mixes with variables such as use of PLC or presence of CA in powder form is considered. In order to address to the lack of research and industry knowledge discussed above, this PhD thesis includes the following phases: Phase (I) In this phase, the main focus is on the microstructural properties and the changes in the pore structure and chemical compositions of the cement phase of mortar mixes when treated with CA. These microstructural features are studied using Scanning Electron Microscope (SEM) and Scanning Transmission Electron Holography Microscope (STEHM). Moreover, physical and chemical characteristics of the hydration products are determined using image analysis and Energy Dispersive X-ray (EDX) Spectroscopy, respectively. Phase (II) This phase is allocated to macro-level investigation of durability characteristics such as chloride/water permeability and electrical resistivity of concrete structures containing CA and PLC cement. To non-destructively measure the chloride ion concentration in the field conditions, both changes in corrosion potential of rebars and concrete electrical resistivity in treated circular hollow-section steel reinforced columns exposed to simulated marine environment is monitored and compared over a 2-year period with control samples. In addition, laboratory-size concrete samples are studied to investigate the effects of CA presence on long-term resistivity, rapid chloride permeability, water permeability and chloride diffusivity of concrete. Later, a resistivity-based model is developed to predict long-term performance of concretes incorporating slag or metakaolin, studied in various environmental conditions. The long-term goal of this phase is to develop a standard design guideline and durability-based model. Phase (III) Using an innovative self-healing testing method [1], quantitative analysis of crack closure ability and self-healing potential of CA treated and control concretes with OPC or PLC cement is accomplished during this phase. The obtained results from first phase showed that hydrated CA particle revealed fine, compact, homogenous morphology examined by STEHM and its diffraction pattern after water-activation indicated nearly amorphous structure, however, diffuse rings, an evidence for short-range structural order and sub-crystalline region, were observed which requires further investigation. The SEM micrographs taken from specimen’s fractured surface showed formation of pore-blocking crystals for all treated mixes while similar spots in un-treated sections were left uncovered. Although needle-shaped crystals were observed in the treated mortar specimens, but not all of them had shapes and chemical compositions other than ettringite (well-known to form needle-like crystals). Using backscatter SEM images and EDX spectrums, examination of polished mortar sections with and without CA also showed typical hydration phases, forming in the control system. Results from phase II showed that concretes treated with CA had almost 50% lower water penetration depth and thus smaller permeability coefficient when compared with the virgin OPC or PLC concretes. According to salt ponding test results, the use of CA helped in enhancing the resistance to chloride penetration compared to control concrete. This improvement increases with increasing in concrete age. Strong linear relationship between Surface Resistivity (SR) and Bulk Resistivity (BR) data was observed which indicates that these test methods can be used interchangeably. The presence of SCM in concrete indicated considerable increase in both SR and BR compared to control concrete. Concretes incorporating slag or metakaolin have tendency to react more slowly (or rapidly in MK case), consume calcium hydroxide over time, form more Calcium Silicate Hydrate (C-S-H) gel, densify internal matrix, and also reduce OH- in the pores’ solution; thus, increase concrete electrical resistivity. For laboratory specimens, environmental conditions such as temperature variation and degree of water saturation indicated considerable effects on electrical resistivity measurements. As temperature or water content of concrete decreases, its electrical resistivity greatly increases by more than 2-3 times from reference environmental condition. This is mostly because of variation or accessibility in electron mobility. Experimental results from field investigation showed that electrical resistivity readings were highly influenced by the presence of rebar and concrete moisture conditions. In addition, concrete cover thickness and CA addition into cementitious matrix had a negligible effect on its resistivity. In the last phase, an optical microscope was used to measure the average crack width. OPC samples had an average measured crack width of 0.244 mm as compared to 0.245 mm for OPC-CA, 0.251 mm for PLC, and 0.247 mm for PLC-CA. Self-healing test results also showed 90% self-healing ratio for CA modified mix within few days after starting experiment. Addition of CA into the mix led to higher rates of healing and full crack closure (width up to 250 µm) when compared to reference concrete. An empirical equation that relates water initial flow rate to the crack width (Q∝〖CW〗^3) was also proposed in this phase. Presence of PLC and CA in the mixture resulted in positive improvement in crack-closing capability and self-healing ratio. / Graduate / 2019-09-11

A aplicação de uma ou mais camadas de tinta sobre as superfícies metálicas é a maneira mais comum e eficaz de proteger os substratos metálicos contra o fenômeno da corrosão. No entanto, os sistemas de pintura podem vir a falhar precocemente por diferentes motivos, causando um ataque corrosivo inesperado no metal a ser protegido. Por esta razão, o processo de repintura em estruturas metálicas é realizado frequentemente para garantir a integridade da estrutura pintada e aumentar sua vida útil. Como o processo de repintura gera impactos econômicos e ambientais, sistemas de pintura capazes de sofrerem uma reparação sem a necessidade de uma intervenção humana, precisam ser desenvolvidos. O encapsulamento de agentes de reparação, com propriedades de formação de filme, em microcápsulas poliméricas é uma excelente alternativa para que os sistemas de pintura se autorreparem, aumentando os intervalos de repintura. Após o processo de encapsulamento, as microcápsulas contendo o agente de reparação são incorporadas na preparação da tinta, para que o sistema de pintura seja aplicado sobre a estrutura metálica. Este tipo de aditivação confere ao revestimento a propriedade de autorreparação, pois quando o sistema de pintura é danificado as microcápsulas são rompidas e liberam o agente de reparação no local danificado, protegendo novamente o substrato metálico. Neste trabalho foi desenvolvido um sistema autorreparador monocomponente, através do microencapsulamento de uma resina a base de éster de epóxi, pelo método de polimerização in-situ. Também foi desenvolvido um sistema autorreparador bicomponente, através do microencapsulamento de uma resina a base de epóxi, pelo método de emulsão e polimerização in-situ de ureia-formaldeído-melamina e do seu endurecedor a base de poliamida, pelo método de extração de solvente em paredes de poliestireno. Foi realizado um planejamento estatístico para estudar a emulsão precursora das microcápsulas de poli(ureia-formaldeído-melamina) contendo o sistema monocomponente, onde foram estudados: o tipo e a velocidade de agitação, a presença de cloreto de sódio na formulação, o uso de uma sonda ultrassônica após a etapa de dispersão, a concentração de tensoativo na formulação e o tensoativo utilizado. Como variáveis de resposta foram determinadas: a estabilidade visual das emulsões e o diâmetro das gotículas formadas. A melhor condição de emulsificação determinada foi utilizada para a obtenção das microcápsulas de poli(ureia-formaldeídomelamina) contendo a resina éster de epóxi e das microcápsulas de poli(ureiaformaldeído-melamina) contento a resina epóxi. Entre as condições de emulsificação estudadas, apenas a condição utilizando o tensoativo goma arábica possibilitou a obtenção das microcápsulas de poli(ureia-formaldeído-melamina) na faixa de diâmetro desejada. O método escolhido para o encapsulamento do endurecedor possibilitou a obtenção de microcápsulas de poliestireno, porém com uma baixa capacidade de armazenamento. A liberação dos agentes de reparação encapsulados foi observada pela microscopia óptica e comprovada pela técnica de espectroscopia na região do infravermelho (FTIR) e pela técnica de espectroscopia Raman. Os aditivos autorreparadores desenvolvidos (mono e bicomponente) foram adicionados separadamente em uma tinta epóxi, nas proporções mássicas em base seca de 10 e 15 %. O sistema de pintura foi aplicado em um esquema de três camadas e o aditivo de autorreparação foi incorporado na primeira e/ou segunda camada aplicada. O sistema de pintura contendo o aditivo autorreparador monocomponente apresentou um aspecto visual melhor do que o sistema de pintura contendo o aditivo autorreparador bicomponente, porém o sistema bicomponente forneceu melhores propriedades de aderência, de impermeabilidade, anticorrosivas e de autorreparação à tinta aditivada. As medidas com as técnicas eletroquímicas de espectroscopia de impedância eletroquímica (EIE) e de varredura com eletrodo vibratório (SVET) comprovaram que os dois aditivos desenvolvidos proporcionaram o efeito autorreparador aos sistemas de pintura aditivados, quando estes foram danificados mecanicamente com uma microbroca ou com um estilete. Ensaios acelerados de corrosão em câmara de névoa salina e ensaios de exposição ao intemperismo natural mostraram que os aditivos desenvolvidos promoveram uma proteção adicional ao aço carbono, quando o sistema de pintura foi danificado mecanicamente. / The application of one or more coating layers on the metallic surfaces is the most common and effective way to protect metallic substrates against corrosion. Nevertheless, the coating layer may fail early for different reasons, leading to an unexpected corrosive attack on the protected metal. For this reason, the coating repair process is performed to ensure the integrity during the service life of the coated metallic structures. Due to the fact that coating repair process generates economic and environmental impacts; there is a great need for the development of systems capable to repair themselves, without human intervention. The encapsulation of repairing agents, with film forming properties, in polymeric microcapsules is an excellent alternative to the coating self-repair, decreasing the coating repair process frequency. After the encapsulation process, the microcapsules containing the repair agent are incorporated into the paint preparation and the coating system could be applied normally to the metallic surface. This kind of additivation confers to the coating the self-healing property, because when the coating system is damaged the microcapsules suffers a rupture and release the repair agent into the damaged site, protecting the metallic substrate from corrosion. In this work, a mono-component self-healing system was developed, through the microencapsulation of an epoxy ester resin, by the in-situ polymerization method. A bi-component self-healing system was also developed, by the microencapsulation of an epoxy resin, through the emulsion and in-situ polymerization method and by the microencapsulation of a polyamide hardener, by the double emulsion and solvent extraction method. A factorial design was developed to study the precursor emulsion of the poly (urea-formaldehyde-melamine) microcapsules containing the monocomponent system, where the studied factors were: the type and speed of the agitation, the presence of sodium chloride in the formulation, the use of an ultrasonic probe after the emulsification, the surfactant type and concentration. The analyzed response variables were: the visual stability of the emulsions and the mean diameter of the formed droplets. The best obtained emulsification conditions were employed to produce the poly(urea-formaldehyde-melamine) microcapsules containing the epoxy ester resin and poly(urea-formaldehyde-melamine) microcapsules containing the epoxy resin. Among the studied emulsification conditions, only using arabic gum surfactant the poly (urea-formaldehyde-melamine) microcapsules were obtained. The selected method for the hardener encapsulation was efficient to obtain polystyrene microcapsules, but with low loading capacity. The release of the encapsulated repair agents was observed by optical microscopy and confirmed by infrared spectroscopy (FTIR) technique and Raman spectroscopy technique. The developed self-healing additives (mono and bicomponent) were added separately in an epoxy commercial coating, using the dry mass ratios 10% and 15 %. The coating system was applied in a three layer coating system and the self-healing additive was incorporated into the first and/or second layer. The coated samples containing the mono-component additive had a better visual appearance than the bi-component additive system; nevertheless the bi-component system provided better adhesion, impermeability, anti-corrosion and self-healing properties to the doped coating. The electrochemical impedance spectroscopy (EIS) and scanning vibrating electrode technique (SVET) measurements proved that the two developed additives provided self-healing properties to the doped coating systems, when they were mechanically damaged with a micro drill or a blade. Accelerated corrosion tests in the salt spray chamber and natural atmospheric corrosion tests showed that the developed additives provided an additional protection to the carbon steel, when the coating system has been mechanically damaged.