O presente trabalho tem como objetivo identificar e analisar parâmetros que influenciam a aderência de matrizes cimentícias a substratos apontando soluções técnicas para a melhoria de tal propriedade. Para tanto, foram desenvolvidos três estudos independentes: primeiro, a elaboração e validação de um modelo matemático com base na restrição geométrica para verificar a contribuição da penetração de partículas em meios porosos. O modelo considera que, após serem lançadas sobre a superfície, as partículas com área de projeção no plano menor ou igual à área do poro podem penetrá-la; segundo, um estudo experimental comparando substratos cimentícios com mesmas características topográficas (rugosidade/porosidade) e diferentes níveis de absorção obtidos mediante tratamentos superficiais: aplicação de silano e lixamento para verificar o efeito da absorção do substrato. O controle da absorção foi realizado por medições do ângulo de contato aparente e ensaios de absortividade; e por último, a influência do teor de ligante da matriz foi avaliada pela substituição de 30% e 60% do cimento por finos calcários, com duas distribuições granulométricas, em argamassas aplicadas sobre blocos cerâmicos. O efeito da aglomeração de partículas foi estudado pela adição de dispersante a base de policarboxilato num teor de 0,02% em relação ao volume total de sólidos. As características reológicas das argamassas foram medidas por reometria rotacional. O desempenho mecânico da interface matriz-substrato foi avaliado pela resistência de aderência ä tração. Os resultados mostraram que a aderência depende de parâmetros mais complexos que a simples absorção do substrato e, consequente ancoragem mecânica pela penetração de partículas nos poros. O uso de partículas finas associadas a dispersantes e tratamentos superficiais do substrato aumentaram aderência pelo acréscimo de contato matriz-substrato. / This study aims to identify and analyse parameters that influence the adhesion among cementitious matrices and substrates pointing out technical solutions to improve this property. The research has been developed by means of three independent studies. The first one concerns the development and validation of a mathematical model, based on geometric constraints, for the estimation of the particles potential penetration in porous media. The model considers particles with projected area less than or equal to the pore area can penetrate the pore. The second study is an experimental comparison among cementitious substrates with same porosity and roughness and different levels of absorption achieved by surface treatment. The application of abrasive methods and a water repellent have been used to manage the effect of the absorption of substrates. The control of wettability and absorption has been carried out by measuring the apparent contact angle and sorptivity. The third one regards the evaluation of binders content in cementitious matrices. Mortars, with two different limestone fines, have been made and applied on red ceramic substrates (clay bricks). The limestone fines, with two different particle size distributions, have been added at rates of 30% and 60% as replacement of binders volume. The agglomeration of particles has been assessed adding a polycarboxylate type admixture (0.02% of total solids volume), whereas the rheological behavior have been determined using a rotational rheometer. The performance of interface between matrix and substrate has been determined measuring the tensile adhesive strength. Results showed that the adhesion depends on parameters more complex than the simple absorption of substrate and the consequent mechanical interlocking of particles into pores. The use of fine particles, combined with the dispersant and with the silane surface treatment increased the adhesion through the increase of the contact area.

O emprego de compósitos na construção civil, como os de matriz cimentícia e pasta reforçada com fibras, tem se disseminado consideravelmente nos últimos anos. Uma grande variedade de fibras sintéticas, como o polipropileno, tem sido utilizada com sucesso para reforçar compósitos cimentícios. No entanto, o interesse mundial na utilização de produtos com menor impacto ambiental estimula a busca por materiais para substituir fibras sintéticas. As fibras vegetais, biodegradáveis, pode ser ótima alternativa devido à abundância, ao baixo custo, ao menor consumo de energia para sua produção e às propriedades mecânicas apropriadas. Fibra de curauá, planta nativa do estado do Amazonas, com plantações em escala comercial, é usada na fabricação de cordas, cestos ou como reforço em matrizes orgânicas. Suas propriedades mecânicas são semelhantes às de polipropileno. A tecnologia de extrusão é viável nas indústrias de fibrocimento, pois produz compósitos com matriz de alta densidade e ótimo empacotamento, baixa permeabilidade e boa adesão fibra matriz. No entanto, o processo de extrusão bem-sucedido de produtos cimentícios depende principalmente das propriedades reológicas do cimento fresco reforçado com fibras. As fibras vegetais podem promover o sequestro de água e interferir fortemente no escoamento, na coesão e no fluxo de pasta de cimento fresco. A incorporação de fibras vegetais influencia os materiais à base de cimento no estado fresco e afeta propriedades no estado endurecido. Neste contexto, o objetivo da pesquisa é avaliar a influência das fibras de curauá e de polipropileno em propriedades reológicas e em propriedades mecânicas da pasta de cimento fresco. Foram preparadas formulações sem fibras, como referência, e com 1 e 2% de reforço em massa, fibras com comprimento de 6 e 10 mm. Utilizaram-se duas técnicas reológicas: Squeeze flow e reômetro extrusor para analisar o fluxo de pastas cimentícias. Por meio de dados experimentais, como força/deslocamento, e de análise numérica da pressão do reômetro extrusor, foram determinados: tensão inicial de cisalhamento (σ0), limite de cisalhamento (τ0), tensão de escoamento (α) e tensão de cisalhamento (β). As propriedades mecânicas foram determinadas em máquina de ensaio MTS. Módulo de ruptura (MOR), tenacidade à fratura (TFT) e energia de fratura (EF) foram calculados. Os resultados reológicos indicam que a pasta cimentícia reforçada com fibras de curauá apresentou maior força, menor deslocamento e aumento da pressão de extrusão em fibras de curauá em relação às pastas cimentícias reforçadas com fibras de polipropileno. O comprimento das fibras influenciou mais o fluxo da mistura do que o teor de fibra. Compósitos cimentícios reforçados com fibra de polipropileno apresentaram melhores resultados mecânicos de MOR, TFT e EF em relação aos compósitos reforçados com curauá. Após os 200 ciclos de envelhecimento, os resultados mecânicos dos compósitos reforçados com as fibras de curauá diminuíram devido a mineralização das fibras. Os resultados de nanoindentação, como dureza e módulo elástico, aumentaram após os 200 ciclos. As metodologias aplicadas para avaliar o comportamento reológico e mecânico do fibrocimento durante a extrusão facilitará a futura transferência dessa tecnologia ao setor produtivo, com produtos potencialmente de melhor qualidade. / The use of composites in construction, as matrix and paste cement reinforced with fibers, has spread considerably in recent years. A wide variety of synthetic fibers such as polypropylene have been successfully used to reinforce cementitious composites. However, worldwide interest in the use of products with lower environmental impact stimulates the search for materials to replace synthetic fiber. Vegetable fiber, biodegradable, can be a great alternative because of the abundance, low cost, the lowest energy consumption for its production, appropriate mechanical properties. Curauá fiber, native plant from Amazon, with crops on a commercial scale, is used in the manufacture of ropes, baskets or as reinforcement in organic matrix. Its mechanical properties are similar to those of polypropylene. Extrusion technology is feasible in the fibercement industry, because it produces composites with high density matrix and great packaging, low permeability and good adhesion fiber matrix. However, successful extrusion process of cementitious products mainly depends on the rheological properties of fresh cement reinforced with fibers. The vegetable fibers can promote water kidnapping and strongly interfere in the flow, cohesion and fresh cement slurry flow. The incorporation of vegetable fibers influences the based cementitious materials in the fresh state and affects properties in the hardened state. In this context, the objective of the research is to evaluate the influence of curauá and polypropylene fiber in rheological and mechanical properties of fresh cement paste. Formulations without fiber, used as reference, 1 and 2% content by weight of reinforcement, fibers with a length of 6 to 10 mm were prepared. Two rheological techniques were used: Squeeze flow and extruder rheometer to analyze the flow of cement pastes. Through experimental data, as strength/displacement and numerical analysis of the pressure extruder rheometer were determined: yield stress corresponding to zero velocity (σ0), initial shear stress (τ0), effect of the velocity on yield stress (α) and effect of velocity in the shear stress (β). The mechanical properties were determined in MTS testing machine. Modulus of rupture (MOR), fracture toughness (TFT) and fracture energy (EF) were calculated. The rheological results indicate that the cement paste reinforced with curauá fiber showed higher strength, smaller displacement and increased extrusion pressure with curauá fibers compared to cementitious paste reinforced with polypropylene fibers. The length of the fibers influence the flow of the mixture more than the fiber content. Composites reinforced with polypropylene fibers presented higher values of MOR, TFT and EF compared to composites reinforced with curauá fiber. After 200 ageing cycles, the mechanical results of composites reinforced with curauá fibers decreased due to mineralization of the fibers. The nanoindentation results, as hardness and elastic modulus, increased after 200 cycles. The methodologies used to assess the rheological and mechanical behavior of fibercement during extrusion facilitate future transfer of this technology to the productive sector, with potentially higher quality products.

Submitted by Irene Nascimento (irene.kessia@ufpe.br) on 2016-06-27T17:06:44Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Dissertação - Dannúbia Ribeiro Pires (PPGECAM_CAA).pdf: 1569346 bytes, checksum: de291d5949502da801c8fef00fcf2b43 (MD5) / Made available in DSpace on 2016-06-27T17:06:44Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Dissertação - Dannúbia Ribeiro Pires (PPGECAM_CAA).pdf: 1569346 bytes, checksum: de291d5949502da801c8fef00fcf2b43 (MD5) Previous issue date: 2016-02-15 / Facepe / A grande demanda de cinza de algaroba gerada nas lavanderias pertencentes ao APL de Pernambuco e sua constituição química prioritária de carbonato de cálcio, caracterizando seu efeito filler, impulsionaram a verificação do comportamento do sistema cimentício quando da substituição do cimento pela cinza nas argamassas de revestimento. O objetivo deste trabalho é utilizar o resíduo, atualmente descartado no ambiente, em materiais cimentícios, de modo a contribuir para o desenvolvimento sustentável, reduzindo o impacto produzido pelo armazenamento e descarte inadequado. Além disso, pretende-se contribuir para a redução da emissão de CO2 causada pelas indústrias cimenteiras e minimizar os custos dos produtos com cimento Portland. Neste trabalho, foi avaliada a influência da substituição do cimento Portland em diferentes porcentagens (0%, 5%, 10% e 20%) nas propriedades nos estados fresco e endurecido das argamassas, aplicando no traço (1-X):2:X:9 (cimento: cal: cinza: areia), em volume, comumente utilizado para emboço e argamassa de assentamento em obras da região. A cinza foi caracterizada física e quimicamente. As propriedades analisadas no estado fresco foram: reologia das argamassas (reometria de mistura, de cisalhamento e compressiva - squezze flow), densidade de massa e teor de ar incorporado e aderência inicial das argamassas no substrato; e no estado endurecido foram: resistência à tração por compressão diametral, resistência potencial de aderência à tração, módulo de elasticidade dinâmico, porosidade e permeabilidade. De acordo com os resultados obtidos nesta pesquisa, a presença da cinza favoreceu, em todas as porcentagens estudadas, a redução no teor de água de amassamento, mantendo a trabalhabilidade das argamassas. As argamassas com teores de 5% de cinza preservam as propriedades do sistema compatíveis com as propriedades da argamassa de referência. Porém, até 10% é possível a introdução deste resíduo, em substituição ao cimento, sem prejuízos aos sistemas cimentícios, proporcionando alterações mínimas em relação à argamassa de referência, sendo promissor o uso desse resíduo em materiais cimentícios. / There is a considerable production of algaroba wood ash in the laundries of the local productive arrangement on the clothing industry in the Agreste Region of Pernambuco. It is possible to apply it as filler due to its mainly chemical constitution as calcium carbonate. Based on these facts, it was evaluated the mortars behaviour when cement is partial replaced by algaroba ashes. This work objectives reuse this residue, currently discarded in the environment, in cementitious materials. In this way, it contributes to the sustainable development by reducing the impact by storage and improper disposal. Moreover, it is intended contributes to reducing CO2 emissions caused by cement industries and minimize the costs of products with Portland cement. This study investigates the influence of the gradual replacement of cement by algaroba ash (0%, 5%, 10% and 20%). It was evaluated the properties of mortars in fresh and hardened states. The mix by volume (1-X):2:X:9 (cement, lime, ash, sand) was studied, taking into account that these alternative mortars can be applied on regional building sites as rendering plaster and laying mortar. The ashes were characterized physically and chemically. It was carried out in the fresh state: rheology of mortars (mixture, compressive and shear rheometers - squeeze flow), mass density, a content of entrained air and initial adherence of the mortars to the substrate; and in the hardened state: diametrical traction, potential adherence, dynamic modulus of elasticity, porosity and permeability. The results indicate that the presence of the ashes decreases the quantity of mixing water required to keep the workability of the mortars, regardless the content of cement replacement content by algaroba ash. The mortar with 5% ash content preserving system properties compatible with the properties of the reference mortar. However, it is possible to partial substitute the cement by algaroba ash until 10% in the studied mortars, when comparing to the reference system, algaroba ashes are a promising material to incorporate in a cementitious system.

A lower-alkalinity cement based on MgO and SiO2 blends is analysed to develop clinker-free Fibre Reinforced Cementitious Composites (FRCC) with cellulosic fibres in order to solve the durability problems of this type of fibres when used in FRCC with Portland cement. Hydration evolution from 7 to 28 days of different MgO-SiO2 formulations is assessed. The main hydration products are Mg(OH)2 and M-S-H gels for all the formulations studied regardless of age. Hardened pastes are obtained with pH values < 11 and good mechanical properties compared to conventional Portland cement. 60% MgO-40% SiO2 system is chosen as optimal for the development FRCC since is the most mechanical resistant and is less alkaline compared with 70% MgO-30% SiO2. FRCC based on magnesium oxide and silica (MgO-SiO2) cement with cellulose fibres are produced to study the durability of lignocellulosic fibres in a lower pH environment than the ordinary Portland cement (PC). Flexural performance and physical tests (apparent porosity, bulk density and water absorption) of samples at 28 days and after 200 accelerated ageing cycles (aac) are compared. Two types of vegetable fibres are utilised: eucalyptus and pine pulps. MgO-SiO2 cement preserves cellulosic fibres integrity after ageing, so composites made out of MgO-SiO2 exhibit significant higher performance after 200 cycles of accelerated ageing than Portland cement composites. High CO2 concentration environment is evaluated as a curing treatment in order to optimise MgO- SiO2 matrices in FRCC. Samples are cured under two different conditions: 1) steam water curing at 55°C and 2) a complementary high CO2 concentration (20% by volume). In carbonated samples, Mg(OH)2 content is clearly lowered while new crystals of hydromagnesite [Mg5 (CO3)4⋅(OH) 2⋅4H2O] are produced. After carbonation, M-S-H gel content is also reduced, suggesting that this phase is also carbonated. Carbonation affects positively to the composite mechanical strength and physical properties with no deleterious effects after ageing since it increases matrix rigidity. The addition of sepiolite in FRCC is studied as a possible additive constituent of the binding matrix. Small cement replacement (1 and 2% wt.) by sepiolite is introduced and studied in hardened cement pastes and, later, in FRCC systems. When used only in cement pastes, it improves Dynamic Modulus of Elasticity over time. Bending tests prove the outcome of this additive on the mechanical performance of the composite: it improves composite homogeneity. Ageing effects are reported after embedding sisal fibres in MgO-SiO2 and PC systems and submitting them to different ageing conditions. This comparative study of fibre degradation applied in different cementitious matrices reveals the real compatibility of lignocellulosic fibres and Mg-based cements. Sisal fibres, even after accelerated ageing, do neither suffer a significant reduction in cellulose content nor in cellulose crystallinity and crystallite size, when exposed to MgO-SiO2 cement. Fibre integrity is preserved and no deposition of cement phases is produced in MgO-SiO2 environment. / Um cimento de baixa alcalinidade à base de blendas de MgO e SiO2 é analisado para o desenvolvimento de Compósitos Cimentícios Reforçados com Fibras (CCRF) celulósicas sem clínquer para resolver os problemas de durabilidade de este tipo de fibras quando são usadas em CCRF com cimento Portland. A evolução da hidratação, desde 7 aos 28 dias, das diferentes formulações é avaliada. Os principais produtos hidratados são o Mg(OH)2 e o gel M-S-H para todas as formulações independentemente da idade estudada. As pastas endurecidas apresentam valores de pH < 11 e bom desempenho mecânico comparado com o cimento Portland convencional. O sistema 60% MgO-40% SiO2 é escolhido como a formulação ótima para o desenvolvimento de CCRF já que é a mais resistente e menos alcalina comparada com 70% MgO-30% SiO2. CCRF com cimento à base de óxido de magnésio e sílica (MgO-SiO2) e fibras celulósicas são produzidos para a análise da durabilidade das fibras lignocelulósicas em ambientes com valores de pH mais baixos comparados com o cimento Portland (PC). O desempenho mecânico a flexão e os ensaios físicos (porosidade aparente, densidade aparente e absorção de água) são comparados aos 28 dias e após de 200 ciclos de envelhecimento acelerado. O cimento à base de MgO-SiO2 preserva a integridade das fibras após o envelhecimento. Os compósitos produzidos com este cimento exibem melhores propriedades após 200 ciclos de envelhecimento acelerado que os compósitos produzidos com cimento Portland. Ambientes com alta concentração de CO2 são avaliados como tratamento de cura para otimizar as matrizes MgO- SiO2 nos CCRF. As amostras são curadas sob 2 condições diferençadas: 1) cura com vapor de água a 55oC e 2) cura com alta concentração de CO2 (20% do volume). As amostras carbonatadas apresentam teores reduzidos de Mg(OH)2 enquanto é produzida uma nova fase cristalina: hidromagnesita [Mg5 (CO3)4⋅(OH) 2⋅4H2O]. Após a carbonatação, o conteúdo de gel M-S-H é reduzido também, indicando uma carbonatação desta fase. A carbonatação aumenta a rigidez da matriz o que influi positivamente no desempenho mecânico e as propriedades físicas dos compósitos sem efeitos prejudiciais ao longo prazo. A adição de sepiolita em CCRF é estudada como possível adição na composição da matriz aglomerante. Baixos teores (1 e 2% em massa) de cimento são substituídos por sepiolita para o estudo das pastas de cimento hidratado e, posteriormente, dos compósitos. O Módulo Elástico Dinâmico das pastas é incrementado com o tempo pela adição de sepiolita. Os ensaios a flexão demostram que a adição de sepiolita melhora a homogeneidade dos compósitos. Reportam-se os efeitos das fibras de sisal após da exposição a sistemas MgO-SiO2 e PC e submetidas a diferentes condições de envelhecimento. Este estudo comparativo da degradação das fibras expostas a diferentes matrizes cimentícias mostra a compatibilidade das fibras lignocelulósicas com os cimentos à base de Mg. As fibras de sisal, inclusive após o envelhecimento acelerado, não apresentam nem redução significativa no conteúdo de celulose nem na cristalinidade da celulose assim como do tamanho de cristalito, quando expostas a cimentos MgO-SiO2.

Made available in DSpace on 2016-03-15T19:36:35Z (GMT). No. of bitstreams: 1 Thais dos Santos Souza.pdf: 11169057 bytes, checksum: 6c199918f7217137c24070f2ea4f8e6e (MD5) Previous issue date: 2012-02-13 / Universidade Presbiteriana Mackenzie / The suitable superplasticizers admixtures usage has become fundamental in the cementitious systems production (like concretes and mortars), because they interact with cement particles surfaces, causing their dispersion and deflocculation without the excessive water addition. The hardened material with a smaller water quantity acquires better positive, like higher compressive strength, lower permeability and extended durability. The major dispersants admixtures are negative charged polymers (polyelectrolytes) that are capable to adsorb on the cement particles and cause their electrostatic dispersion. Given the current environmental and economic interest in reuse of discarded materials, the purpose of this study was to assess the viability of use and application of modified post-consumer expanded polystyrene (EPS) as an admixture to cementitious systems becoming it a higher added value material. The modification of the EPS was performed by sulfonation and the interfering variables in the reaction were evaluated. The performance of the stabilized polyelectrolyte already formed (sodium polystyrene sulfonate NaPSS) as dispersant was verified in cement paste and mortar. The study showed that modification of post-consumer EPS by sulfonation reaction was carried out efficiently regarding to the production of a polyelectrolyte with a maximum degree of modification, within the conditions studied, and which variables most influence the reaction. Moreover, the product with a maximum degree of modification (most likely to interact with the cement) was not effective as a dispersant for cementitious systems, causing a decrease in the mechanical strength and plasticity evaluated. / O uso de aditivos plastificantes adequados tornou-se fundamental na produção de sistemas cimentícios (como por exemplo, concretos e argamassas), pois interagem com a superfície das partículas de cimento, provocando a dispersão e defloculação das mesmas, sem adição excessiva de água. O material endurecido adquire assim melhores propriedades, como maior resistência, menor permeabilidade e maior durabilidade. Grande parte dos aditivos dispersantes são polímeros dotados de cargas negativas (polieletrólitos), capazes de adsorver nas partículas de cimento e provocar sua dispersão eletrostática. Diante do atual interesse ambiental e econômico de reutilização dos materiais descartados, o propósito deste trabalho foi verificar a viabilidade do uso e aplicação do EPS pós-consumo modificado como aditivo plastificante de sistemas cimentícios, tornando-o um material de maior valor agregado. A modificação do EPS foi realizada via sulfonação, e as variáveis interferentes na reação foram avaliadas. O polieletrólito formado já estabilizado (poliestireno sulfonado de sódio PSSNa), teve seu desempenho como dispersante verificado em pasta de cimento e argamassa. O estudo mostrou que a modificação do EPS pós-consumo a partir da reação de sulfonação realizada foi eficiente com relação à produção de um polieletrólito com máximo grau de modificação, dentro das condições estudadas, e quais as variáveis que mais influenciam na reação. Por outro lado, o produto com máximo grau de modificação (mais passível de interação com o cimento) não se mostrou eficiente como dispersante de sistemas cimentícios, causando a diminuição da plasticidade e das resistências mecânicas avaliadas.

O espaço de discussão dos impactos sociais e ambientais das atividades humanas tem ganhado mais relevância nos últimos anos, dentro e fora da Universidade. A engenharia, como área do conhecimento que influencia fortemente o mercado da construção civil, que representa cerca de 10% do PIB nacional, tem uma responsabilidade na criação e fomento de espaços para estudo dessa questão. O Projeto Crescimento, objeto de estudo da pesquisa aqui colocada, tem o propósito de auxiliar nessa discussão, por meio da montagem de uma fábrica protótipo de peças cimentícias em local de alta vulnerabilidade social, com a função de aumentar de qualidade de vida daqueles que participam das atividades na fábrica e das comunidades em seu entorno, por meio do ofício e renda gerados, combinados com um programa de educação que sustenta a mudança em um nível mais profundo. A melhora proposta pode ser medida através de parâmetros objetivos e relatos subjetivos. A iniciativa se baseia na pesquisa em tecnologia de materiais e na produção dos mesmos, combinada com estudos de parâmetros de mercado da construção civil e na economia solidária. A economia solidária, por sua vez, está embasada em novas formas de pensar as relações econômicas e organizá-las no espaço e no tempo, visando uma distribuição do trabalho e seus resultados igualitária e com significado para aqueles que participam da cadeia de dado produto. O produto escolhido para iniciar o projeto foram as peças cimentícias, pela sua facilidade de produção, que pode ser realizada em locais de características variadas, o alto consumo no segmento da construção e a existência prévia de uma tecnologia já desenvolvida dentro do laboratório de microestruturas da Universidade de São Paulo. Além dos objetivos práticos da abertura da fábrica protótipo, a pesquisa se propõe a descrever as diversas maneiras encontradas de tornar o projeto viável, auxiliando na construção de um caminho mais claro para outras iniciativas similares. Dentro do escopo do estudo proposto, também consta o avanço na tecnologia previamente existente, por meio da criação de peças protótipo, foram obtidos os resultados relevantes em termos de desempenho de materiais, comparando-os com normas e requisitos nacionais e internacionais. Assim, foi criado um protótipo funcional de fábrica, com a participação dos moradores de rua da região do Glicério, no centro da cidade de São Paulo. Lá foram testados métodos produtivos, a robustez da fórmula desenvolvida e a inserção social do projeto. A partir da comparação entre os resultados obtidos em campo e em laboratório e das informações extraídas da literatura, espera-se avançar no modelo da economia solidária para eventualmente expandi-lo e aperfeiçoá-lo. / The discussion about the social and environmental impacts of human activity are becoming more relevant each year, inside and outside the scope of University and Industry. Engineering, as a knowledge that greatly influences the construction segment, which represents about 10% of the Brazil\'s GDP, has a responsibility in creating and promoting spaces for the discussion and study of this theme. The objective of the research here-by proposed is to add new information to this discussion by structuring a prototype of an advanced cementitious component factory in high social vulnerability areas, with the purpose of raising the quality of life of those participating in the production and the communities surrounding them, through the craft and pay generated, combined with an educational program, that subsidizes the project at a more profound level. The improvement can be measured with objective parameters and subjective narratives. This initiative is based on the materials research, combined with the study of the construction segment and the solidarity economy. Solidarity economy can be translated by rethinking economic organization and relations in space and time, aimed at a more egalitarian and meaningful distribution of work and its outcomes. The product chosen to start this project are cementitious artifacts, because of the possibility of a modular production, that can be structured in a wide variety of environments, its high consumption in the construction segment and the existence of a well-developed cement material technology, in the microstructure laboratory of the University of São Paulo. Aside from the practical objectives described, this research aims to describe the different ways of making this kind of project viable, there by contributing toward building a clearer path toward similar initiatives. Within the work scope, advancements in the material technology were made, through the production of prototypes, so that relevant data about performance could be obtained and compared with national and international standards. That way, a functioning factory prototype was structured with the collaboration of an organized group of homeless people in the Glicério region in the city center of São Paulo. It was there that the community receptivity, production methods and the cementitious formula\'s robustness were tested. By comparing the results obtained in the field research, in the laboratory, and the academic knowledge on the theme, it is hoped that advancements can be achieved in the materials research and the solidarity economy model.

La cristallisation du sel dans les pores peut conduire à l'expansion d'une variété de milieux poreux, y compris le béton, la pierre ou les sols. Par exemple, les attaques sulfatiques de matériaux cimentaires peuvent conduire à des cristallisations du gypse ou de l’ettringite, qui peuvent causer un endommagement et limiter la durabilité des structures en béton. Une meilleure compréhension de la façon dont la cristallisation induit la déformation des matériaux cimentaires est une condition préalable à la conception de moyens efficaces pour atténuer les effets néfastes de la cristallisation du sel. Dans cette thèse, nous cherchons à comprendre comment la cristallisation conduit à l'expansion, pour les matériaux à base de ciment dans le cas spécifique de la présence d'ions sulfatiques, qui est un cas pertinent pour la compréhension des attaques sulfatiques. La principale originalité de l'étude a été de réaliser des expériences avec des matériaux granulaires compactés dans des cellules œdométriques ou isochores. Les échantillons testés ont été fabriqués par broyage de pâtes de C3S, de pâtes de ciment Portland ordinaire, ou des mélanges des phases dont ces pâtes sont constituées (par exemple, monosulfoaluminate AFm), puis de les compacter dans des éprouvettes cylindriques sur une hauteur de 2 cm. Dans les cellules, les échantillons compactés sont très perméables et peuvent être saturés avec des solutions de sulfate de sodium en moins d’1 heure. Dans une cellule œdométrique, l'échantillon est empêché de se dilater radialement, mais est autorisé à se dilater axialement: nous avons mesuré comment des injections de solutions induisent une expansion axiale. Dans une cellule isochore, l'échantillon est empêché de se dilater à la fois radialement et axialement: nous avons mesuré comment des injections de solutions provoquent le développement de contraintes axiales et radiales. Un point notable des cellules isochores que nous avons développées est que toute solution s’évacue le long de l'échantillon et peut être récupérée: ainsi, à partir des mesures des concentrations et des volumes de solutions d'entrée et de sortie, la quantité de sulfates restant dans l'échantillon au cours des expériences pourrait être déterminée. En parallèle des mesures de déformation/contrainte, nous avons effectué des caractérisations minéralogiques et microstructurales des échantillons en utilisant une variété de techniques, notamment : la fluorescence X, l’analyse thermogravimétrique, la diffraction des rayons X, la résonance magnétique nucléaire d'aluminium et la microscopie électronique à balayage avec analyse aux rayons X. Les évolutions des concentrations de sortie et de la minéralogie au cours du processus d'injection ont pu être bien prédites avec le logiciel CHESS de modélisation géochimique. Les résultats expérimentaux de la campagne, en conjonction avec les résultats des caractérisations minéralogiques et microstructurales, ont permis de révéler quels sont les principaux paramètres qui régissent l'expansion. Grâce à ce protocole original que nous avons développé, l'expansion ou le développement de contraintes a commencé immédiatement après l'injection de la solution, s’est stabilisé au bout de quelques jours à quelques semaines, et la cristallisation a eu lieu de façon homogène sur toute la hauteur de l'échantillon. En outre, nous avons montré que la cristallisation du gypse contribue à l'expansion. Dans les tests isochores, nous montrons que les deux cristallisations d'ettringite et de gypse peuvent induire des contraintes, et que l'amplitude de ces contraintes dépend linéairement du volume de ces cristaux formés. Les conclusions tirées de cette étude expérimentale permettent de mieux comprendre les processus physiques par lesquels la cristallisation induit une expansion ou des contraintes dans des solides poreux, et permettent d’orienter la modélisation des attaques sulfatiques dans les matériaux cimentaires / In-pore crystallization can lead to expansion of a variety of porous media, including concrete, stone, or soils. For instance, sulfate attacks of cement-based materials can lead to crystallizations of gypsum or ettringite, which may cause damage and limit the durability of concrete structures. A better understanding of how crystallization induces deformation of cementitious materials is a prerequisite to designing efficient ways of mitigating the detrimental effects of salt crystallization. In this thesis, we aim at understanding how crystallization leads to expansion, for cement-based materials in the specific case of the presence of sulfate ions, which is relevant for sulfate attacks. The main originality of the study was to perform experiments with granular materials compacted into oedometric or isochoric cells. The tested samples were manufactured by grinding C3S pastes, regular Portland cement pastes, or mixtures of phases of which those pastes are made (e.g., monosulfoaluminate AFm), and then compacting them within the cell into 2-cm-high cylindrical specimens. In the cells, the highly permeable compacted samples could be flushed with sodium sulfate solutions in less than 1 hour. In an oedometric cell, the sample is prevented from expanding radially, but is allowed to expand axially: we measured how injections of solutions induced an axial expansion. In an isochoric cell, the sample is prevented from expanding both radially and axially: we measured how injections of solutions induced the development of axial and radial stresses. A salient feature of the isochoric cells we developed is that all solution flushed throughout the sample could be recovered: thus, from the measurements of concentrations and volumes of input and output solutions, the amount of sulfate remaining in the sample over the experiments could be determined. In parallel to the deformation/stress measurements, we also performed the mineralogical and microstructural characterizations of the samples before and after testing by using a variety of techniques, including X-ray fluorescence, thermogravimetric analysis, X-ray diffraction, aluminum nuclear magnetic resonance and scanning electron microscopy with X-ray analysis. The evolutions of the output concentrations and of the mineralogy over the injection process could be well predicted with the geochemical modeling software CHESS. Experimental results of the campaign, in conjunction with results from mineralogical and microstructural characterizations, made it possible to reveal what the main parameters are that govern expansion. Thanks to the original protocol we developed, expansion or development of stresses started immediately after the injection of solution, stabilized after a few days to a few dozen days, and crystallization occurred homogeneously throughout the height of the sample. One interesting conclusion is that, even when ettringite crystallizes in macropores, i.e., outside of the C-S-H gel porosity, ettringite can lead to an expansion. Also, we showed that gypsum crystallization contributes to expansion. In isochoric testing, we showed that both crystallization of ettringite and of gypsum can induce stresses, and that the magnitude of those stresses is linearly related to the volume of those crystals formed. The conclusions drawn from this experimental study make it possible to better understand the physical processes through which crystallization induces expansion or stresses in porous solids, and thus to orient the modeling of sulfate attacks in cement-based materials

EU Sustainable Development Strategy planned to achieve improvement of life-quality by promoting sustainable production and consumption of raw materials. On November 2018, EU Commission presented a long-term strategy, aiming among others a climate-neutral economy by 2050. Cement production is contributing to 6-10% of the anthropogenic CO2 emissions. Thus, several strategies for total or partial replacement of Portland cement in concrete production have been developed. The use of supplementary cementitious materials (SCM) and alkali-activated materials (AAM) is considered the most efficient countermeasure to diminish CO2 emissions. The broadening of knowledge with particular attention to the sustainable goals is the primary requirement to be fulfilled when novel materials are investigated. This study aims to develop a novel clay-based binder that can be used as a sustainable alternative to produce SCM as well as AAM. Clay is a commonly occurring material, with large deposits worldwide. However, natural clay has a low reactivity and various compositions, depending, e.g. on the weathering conditions. The present research aims exactly at enhancing the reactivity of natural clays occurring in Sweden subjecting them to mechanical activation in a planetary ball mill. Ball milling (BM) is considered a clean technology able to enhance the reactivity of crystalline materials without resorting to high processing temperatures or additional chemicals. BM was able to induce amorphization in clay minerals and to transform the layered platy morphology to spherical shape particles. The efficiency of the process was strictly related to the used process parameters. Higher ball to processed powder (B/P) ratio, longer time of grinding and higher grinding speeds increased the degree of the obtained amorphization. However, an undesired extensive caking and agglomeration occurred in certain setups. The potential of activated clay as a SCM was investigated in specific case studies. The measured compressive strength results showed a direct correlation between the enhanced amorphization degree of the mechanically activated clay and the increased strength values. The pozzolanic activity was induced and enhanced after the mechanical activation of the clay. The reactivity was assessed by the strength activity index (SAI). Furthermore, preliminary tests have shown that the alkali activation of the processed clays produced solidified matrixes with considerable strength.

<div> <p>The formation of the cracks in concrete materials can shorten the service life of the structure by exposing the steel rebar to the aggressive substances from the external environment. Self-healing concrete can eliminate the crack automatically, which has the potential to replace manual rehabilitation and repairing work. This thesis intends to develop a self-healing fiber-reinforced cementitious composite by the use of internal curing agents, such as lightweight aggregate, zeolite and superabsorbent polymer (SAP). This study has evaluated the crack width control ability of three different types of fiber, polyvinyl alcohol fiber (PVA), Masterfiber Mac Matrix and Strux 90/40 fiber. Mechanical performance and flexural stress-strain behavior of the fiber-reinforced cementitious composite were tested and compared. In order to investigate the feasibility of using internal curing aggregate to enhance autogenous healing performance, two types of porous aggregates, zeolite and lightweight aggregate (LWA), were used as internal curing agents to provide water for the autogenous healing. The pore structure of the zeolite and lightweight aggregate was examined by the scanning electron microscopy (SEM). Two replacement ratios of sand with internal curing aggregates were designed and the healing efficiency was evaluated by the resonant frequency measurement and the optical microscopic observation. To further understand the influence of the internal curing on the designed material, water retention behavior of the bulk sample and the internal curing aggregates was evaluated. Moreover, to study the self-sealing effect of the superabsorbent polymer (SAP), the robustness of the SAP under various environmental conditions was first evaluated. The influence of the superplasticizer, hydration accelerator and fly ash on the absorption behavior of the SAP was investigated by the filtration test and void size analysis. Afterward, the self-sealing performance of the SAP in cement paste was evaluated by a water flow test.</p> <p>The evaluation of three types of fiber indicated that the use of PVA fiber could produce a cementitious composite with stronger mechanical strength and crack width control ability. The result of the autogenous healing evaluation showed that the incorporation of the internal curing aggregates increased the self-healing recovery ratio from 12.6% to over 18%. The internal curing aggregate could absorb and store water during the wet curing and release it when the external water supply is unavailable. The comparison between the two types of internal curing aggregates indicated that finer pores in the internal curing aggregate can lead to a slower water release rate that is capable of continuously supplying water for the autogenous healing. In addition, the SAP was proved to be robust when various content of the additives and fly ash were used. And the self-sealing effect of the SAP is found to be effective in regaining the water tightness of cement paste. The result of this thesis can assist in the design of the fiber-reinforced cementitious composite with self-healing performance in civil engineering.</p> </div> <br>

Concrete is essential for the construction industry with characteristic properties that make it irreplaceable in some aspects. However, due to the large volumes consumed and the energy intense cement clinker production it also has a notable climate impact. In order to reach the international and national sustainability goals it is therefore important to reduce the climate impact of concrete structures. There are many ways to influence the environmental impact of concrete and a detailed analysis is one of the actions that could push the industry and the society towards a sustainable development. The purpose of this research is to evaluate the environmental impact of concrete structures and the built environment and to highlight the possibilities to reduce that impact with choice of concrete mix and innovative design solutions. A life cycle assessment (LCA) was carried out to analyze the environmental impact of two thin façade solutions with innovative materials and to evaluate influences of different greenhouse gas reducing measures on concrete bridges. The influence of supplementary cementitious materials (SCM) in terms of climate impact and durability was also analyzed. The results indicate that SCMs have a twofold effect on the climate impact of reinforced concrete structures. Not only do they reduce the greenhouse gases through cement clinker replacement but also by an improvement of durability regarding chloride ingress. Currently, this is not considered in the regulations, which makes it difficult to foresee in LCA at early design stages. The results also show great possibilities to reduce the climate impact through different measures and design alternatives and the need for further development of products and solutions. / <p>QC 20171002</p>