O metacaulim é um material pozolânico que vem sendo pesquisado e adotado em vários países. O metacaulim é constituído basicamente de sílica (SiO) e alumina (Al2O3) na fase amorfa, capaz de reagir com o hidróxido de cálcio Ca(OH) gerado durante a hidratação do cimento Portland, formando produtos hidratados similares aos decorrentes da hidratação direta do clinquer Portland. Esta pozolana acelera o processo de hidratação do cimento, formando silicato de cálcio hidratado (C-S-H) adicional. O conhecimento das características do metacaulim que influenciam a interação com a cal, se faz necessário para subsidiar medidas preventivas com relação ao consumo de portlandita. O presente trabalho visa determinar as características físico-químicas relevantes para o entendimento da atividade pozolânica, avaliando as reações propiciadas pelo metacaulim em sistemas binários. Para este propósito, realizaram-se estudos experimentais em pasta e concreto, usando as técnicas de difratometria de raios X e de termogravimetria. As etapas experimentais consistiram: na caracterização do metacaulim, com ênfase na determinação do teor da fase amorfa; a avaliação da cinética da reação em sistema metacaulim/hidróxido de cálcio e análise da evolução da hidratação de cimento com alto teor de metacaulim. Nos sistemas cimenticios de concretos com diferentes teores de substituição de metacaulim com e sem cal hidratada, foi avaliado o comportamento da resistência à compressão. No metacaulim estudado, o teor da fase amorfa foi de 74,60% e o restante (25,40%) atua como material inerte, e o consumo máximo por atividade pozolânica, foi de 1,34 gr de Ca(OH)/grama de fase amorfa de metacaulim. Na evolução das reações, por atividade pozolânica o C-S-H foi formando gradativamente. A adição de 15% de metacaulim e 5% de cal hidratada em concretos proporcionou um ganho de resistência de 17% a mais em função do concreto de referência. / The metakaolin is a pozzolanic material that has been investigated and adopted in several countries. The metakaolin consists primarily of silica (SiO) and alumina (Al2O3) in the amorphous phase, and can react with calcium hydroxide Ca (OH) generated during hydration of Portland cement to form products similar to those obtained during Portland clinker basic hydration. This pozzolana could accelerate the hydration of cement, forming calcium silicate hydrate (C-S-H) additional. The knowledge of the characteristics of metakaolin that influence the interaction with lime provides the necessary subsidize to prevent excessive consumption of portlandite. This paper aims to determine the physical and chemical relevant characteristics in order to understand the pozzolanic activity, evaluating the responses provided by the metakaolin in binary systems. For this purpose, experimental studies were conducted in paste and concrete, using the techniques of X-ray diffraction and thermogravimetry. The experimental steps consisted of: the characterization of metakaolin, with emphasis on determining the amorphous phase content, this evaluation of the kinetics of the reaction system metakaolin and calcium hydroxide; The analysis of the evolution of the cement hydration with high content of metakaolin. In cementitious systems of concrete with different metakaolin replacement levels with and without hydrated lime, was rated the behavior of the compressive strength. The content of amorphous phase In the studied metakaolim was 74.60% and the remainder (25.40%) acts as an inert material, and the máximum consumption by pozzolanic activity was 1.34 g of Ca (OH)/g amorphous phase of metakaolin. During the evolution of pozzolanic reactions, the C-S-H was gradually formed. The addition of 15% metakaolin and 5% hydrated lime in concrete has a strength gain of 17% more depending on the reference concrete.

Submitted by Fabio Sobreira Campos da Costa (fabio.sobreira@ufpe.br) on 2016-06-14T13:59:39Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Marcela - Dissertação.final.pdf certa.pdf: 5757501 bytes, checksum: cbb31e84ba5e0fb9aeafa824e3565b87 (MD5) / Made available in DSpace on 2016-06-14T13:59:40Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Marcela - Dissertação.final.pdf certa.pdf: 5757501 bytes, checksum: cbb31e84ba5e0fb9aeafa824e3565b87 (MD5) Previous issue date: 2013-08-30 / CAPEs / Existem resíduos de processos industriais que são característicos do estado de Pernambuco, como o bagaço de cana-de-açúcar, e que são poucos abordados por estudos sistemáticos para o seu emprego na construção civil. O estudo consiste em comparar a atividade pozolânica da cinza do bagaço de cana-de-açúcar (CBCA) e de um material comprovadamente pozolânico fazendo uso dos ensaios tradicionais de determinação de atividade pozolânica. Existem diversos métodos considerados tradicionais, geralmente divididos nos que mensuram um parâmetro de resistência mecânica (definidos como “métodos físicos”) e nos que mensuram de forma direta ou indireta a reação química que caracteriza a existência da atividade pozolânica (definidos como “métodos químicos”). A abordagem desta questão será utilizar métodos físicos previstos por normas brasileiras e métodos físicos modificados para a determinação da atividade pozolânica. No intuito de apontar caminhos para a utilização deste resíduo na construção civil, o presente trabalho apresenta os resultados da análise de 29 amostras de cinza que receberam diferentes tratamentos térmicos e físicos e mais a análise do metacaulim que foi utilizado como material pozolânico de referência. Todas as amostras foram caracterizadas por difração de raios-X e passaram pelos ensaios mecânicos previstos nas normas NBR 5751:1992 e NBR 5752:1992 para determinação do índice de atividade pozolânica.De acordo com os resultados obtidos, evidenciou-se que os métodos normatizados não apresentam respostas totalmente congruentes, pois, a atividade pozolânica foi constatada pelo método de atividade com cimento Portland (IAP), porém não foi constatada pelo método de atividade com cal hidratada. A CBCA “in natura” apresentou IAP superior ao estabelecido pela NBR 12653:1992 (75%) quando do aumento do grau de moagem, assim como a CBCA calcinada a 600ºC. A moagem mostrou ser de fundamental importância para o aumento do potencial pozolânico da CBCA, concluindo-se que finura Blaine deve ser superior a 500 m2/kg. A temperatura de calcinação se mostrou relevante quando aplicação de 600ºC, acima deste valor ocorreu o decréscimo dos índices de pozolanicidade. / There are residues of industrial processes that are characteristic of the state of Pernambuco, as bagasse from sugar, and few addressed by systematic studies for your construction jobs. The study is to compare the pozzolanic activity of bagasse ash from sugar cane (CBCA) and a pozzolanic material shown making use of traditional tests to determine pozzolanic activity. Several methods are considered traditional, generally divided in that measure a parameter of mechanical resistance (defined as "physical methods") and in that measure directly or indirectly the chemical reaction that characterizes the existence of pozzolanic activity (defined as "chemical methods"). The approach to this issue is to use physical methods provided by modified for the determination of pozzolanicity Brazilian standards and physical methods. In order to point out ways to use this waste in construction, this paper presents the results of analysis of 29 samples of gray that received different thermal and physical treatments and more analysis that metakaolinpozzolanic material was used as reference. All samples were characterized by X-ray diffraction and passed by the expected in NBR 5751:1992 and NBR 5752:1992 standards for determining the pozzolanic activity index mechanical tests. According to the results, it was evident that standardized methods have not fully congruent answers, because the pozzolanic activity was observed by the method of activity with Portland (IAP) cement, but was not detected by the method of activity with hydrated lime. The CBCA "in natura" made higher than in theNBR 12653:1992 (75%) while increasing the fineness of grind, and calcined at 600°C CBCA IAP. The grinding proved to be of fundamental importance to increase the potential of pozzolanic CBCA, concluding that Blaine fineness must be greater than 500 m2 / kg. The calcination temperature was also relevant when applying 600°C, above this value was decreasing rates of pozzolanicity.

O concreto é um dos materiais mais utilizados pela indústria da construção civil. Apesar de novos materiais terem entrado no setor da construção, ele não perdeu o seu valor devido as suas boas propriedades mecânicas, baixo custo e a alta flexibilidade construtiva. O concreto é responsável por uma parcela significativa do impacto humano ao meio ambiente, mas apesar de tudo é um dos materiais mais empregados e importantes da atualidade. A necessidade em agregar valor à grande quantidade de resíduos gerados no mundo é uma oportunidade para inclusão de novos materiais na formulação dos concretos, em substituição aos tradicionais. Quando as matérias-primas naturais são substituídas por resíduos sólidos, vários benefícios são alcançados, como a conservação dos recursos naturais, minimização da eliminação inadequada de rejeitos e liberação de áreas para fins mais nobres. Resíduos de vidro podem ser considerados como potenciais componentes do concreto e a sua utilização na produção dos mesmos impede a sua simples disposição em aterros. Dependendo do tamanho da partícula e da proporção de vidro utilizada na produção de concreto, comportamentos opostos podem ser observados: i) a reação álcali sílica relacionada a efeitos negativos de expansão, e ii) a reação pozolânica que melhora a resistência mecânica. Com a finalidade de promover o uso sustentável das matérias-primas amazônicas na construção civil de Manaus, foram produzidos concretos convencionais empregando-se seixo de rio e brita granítica como agregados graúdos, levando-se em conta fatores como disponibilidade regional e melhores características mecânicas. Os resultados de resistência à compressão axial e tração por compressão diametral entre os concretos produzidos com os dois tipos de agregados não apresentaram diferenças significativas. Com os resultados da pesquisa para o concreto convencional, realizou-se o desenvolvimento de concretos de alta resistência. Nesta fase, a pesquisa avaliou o efeito de resíduos de vidro moído em adição ou substituição ao cimento Portland na resistência mecânica de concretos, através de ensaios de compressão axial e tração por compressão diametral aos 7, 14, 21, 28 e 90 dias de cura, como resultado da atividade pozolânica do pó de vidro abaixo de 75 μm. O nível mais adequado de substituição do cimento por pó de vidro foi de 10%, que apresentou acréscimo de resistência à compressão axial de 69 MPa para 71 MPa aos 90 dias em comparação ao concreto convencional, enquanto que as misturas com adição de vidro apresentaram crescimento em praticamente todas as idades, comparadas à mistura de controle. A pesquisa também avaliou o desempenho de misturas com substituição e adição de sílica ativa, que apresentaram melhores resultados de resistência em relação às misturas contendo apenas pó de vidro reciclado. Os resultados obtidos mostraram que tanto o vidro em pó quanto a sílica têm efeito significativo na resistência do concreto. / Concrete is one of the materials most used by the construction industry. Although new materials entered the construction industry, it did not lose its value due to its good mechanical properties, low cost and high constructive flexibility. Concrete is responsible for a significant portion of the human impact on the environment, but it is one of the most used and important materials nowadays. The need to add value to the large amount of waste generated in the world is an opportunity to include new materials in the formulation of concrete instead of traditional ones. When natural raw materials are replaced by solid waste, several benefits are achieved, such as conserving natural resources, minimizing the improper disposal of waste, and releasing areas for nobler purposes. Glass waste can be considered as potential components of the concrete and its use in the production of these prevents its simple disposal in landfills. Depending on the particle size and the glass ratio used in concrete production, opposite behaviors can be observed: i) the silica alkali reaction related to negative expansion effects, and ii) the pozzolanic reaction that improves mechanical strength. In order to promote the sustainable use of Amazonian raw materials in the civil construction of Manaus, conventional concretes were produced by using river pebbles and granite gravel as large aggregates, taking into account factors such as regional availability and better mechanical characteristics. The results of axial compressive strength and diametral compression traction between the concretes produced with the two types of aggregates did not present significant differences. With the results of the research for the conventional concrete, the development of concrete of high resistance was carried out. In this phase, the research evaluated the effect of ground glass residues on addition or substitution to Portland cement in the mechanical strength of concretes, through axial compression and diametral compression traction at 7, 14, 21, 28 and 90 days of cure, as a result of the pozzolanic activity of the glass powder below 75 μm. The most adequate level of substitution of cement by glass powder was 10%, which presented increase of axial compressive strength from 69 MPa to 71 MPa at 90 days in comparison to conventional concrete, while the mixtures with glass added showed growth at almost all ages, compared to the control mix. The research also evaluated the performance of mixtures with substitution and addition of active silica, which presented better resistance results compared to mixtures containing only recycled glass powder. The results showed that both glass and silica have a significant effect on the strength of the concrete.

A questão central deste trabalho é demonstrar a viabilidade técnica e econômica da estabilização de solos com os cimentos pozolânicos de cinza de casca de arroz e de resíduo cerâmico. Para alcançar este objetivo o trabalho foi desenvolvido em duas etapas: a primeira referente ao desenvolvimento dos cimentos pozolânicos e a segunda referente à estabilização do solo propriamente dita. Em ambas as etapas adotou-se o critério da simplicidade e da possibilidade de utilização de equipamentos leves e de absorção de mão-de-obra não especializada. Os resultados técnicos e econômicos referentes ao cimento pozolânico de cinza de casca de arroz foram animadores; porém o mesmo não ocorreu com o cimento pozolânico de resíduo cerâmico que apresentou um desempenho em um patamar inferior. Quanto à estabilização de solos, os experimentos e a avaliação econômica efetuada mostram que a eficácia dos cimentos pozolânicos utilizados é limitada sendo difícil a obtenção de resultados comparáveis com o atualmente obtido com o cimento Portland. / The main scope of this work is to demonstrate the technical and economical viability of the soil stabilization with pozzolanic cements made from rice husk ash and waste bricks and tiles. In order to reach this objective the work has been developed in two stages: the first referes to the development of the pozzolanic cement and the second one referes to the soil stabilization. In both these stages the criteria that has been adopted was of the simplicity, of the use of light equipments and of non skilled labour. The technical and economical results referring to the rice husk ash pozzolanic cement were encouraging; but the same was not the case with the waste bricks and tiles pozzolanic cement that had an inferior performance. As regards the soil stabilization, the tests and the economical evaluation show that the efficiency of the pozzolanic cement is limited thus the results achieved are not as good as of the Portland cement.

The doctoral thesis deals with the reactivity of burnt clays in connection with modified lime mortars. The theoretical part of the doctoral thesis provides an overview of the properties of lime mortars, their quality and ways of their degradation. The different types of burnt clays (brick powder, bentonites and burnt clay shale), their origin, properties and factors affecting their reactivity and methods of its evaluation are stated. The properties and reactivity of burnt clays are evaluated on the basis of determination of pozzolanic activity, mineralogical and chemical composition, surface area, density, content of the amorphous phase and granulometry in the experimental part of the doctoral thesis. The compositions of lime mortars containing burnt clays and evaluation of an impact of burnt clay on the properties of mortars in the fresh and hardened state are given. Consistency, bulk density, workability and air content of mortars in the fresh state are evaluated. Strength characteristics depending on the time, water absorbability, porosity, capillary attraction, adhesion, coefficient of diffusion resistance, frost resistance, shrinkage, mineralogical composition and microstructure of mortars in the hardened state are evaluated. Attention is also paid to the influence of the cellulose ether addition into the modified lime mortars.

Biomass represents an important sustainable energy resource, with biomass-coal cofiring representing among the most effective and cost efficient CO2 reduction strategies. Fly ash generated during coal combustion represents a technically advantageous, inexpensive, and environmentally beneficial admixture in concrete production, partially replacing cement. However, strict interpretation of American Society of Testing and Materials (ASTM) and American Concrete Institute (ACI) standards prohibits use of fly ashes from any source other than coal in concrete production; therefore, fly ash from biomass coal cofiring is excluded from use in concrete. This dissertation discusses biomass impacts on concrete properties through experiments conducted on several combinations of blended and pure biomass fly ash in concrete mixtures to determine the effects on freshly mixed concrete, strength and durability of hardened concrete, and implication for long-term material properties. The results show that the performance of biomass and blended biomass-coal fly ash is comparable to that of traditional (neat) coal fly ash. Pozzolanic reactions occur simultaneously but not necessarily proportionally to strength development. Mixtures of biomass and coal fly ash in all proportions mitigate alkali-silica-reaction-based (ASR-based) expansion in concrete. Biomass-specific results indicate that biomass-containing fly ash samples can generate 3-6 times the strength of some neat coal fly ash samples in terms of pozzolanic reactions and that biomass-containing fly ash samples have better or comparable ASR mitigation performance relative to neat coal fly ash. Biomass fly ash applications in concrete production involve pozzolanic, cementitious, and ASR reactions in combination with mixture compositions and preparation techniques to dictate ultimate properties. In these practical applications, biomass fly ash demonstrates no consistent improvement or deprecation of concrete properties relative to coal fly ash. Quantitative pozzolanic reaction mechanism and kinetic analyses indicate biomass and coal fly ashes exhibit comparable reaction rates and react by similar mechanisms. The general conclusion from the experiments is that biomass-containing fly ash, when used in concrete, performs comparable to or better than similar neat coal fly ash preparations in most respects; Substantial efforts were made to ensure samples represent typical commercial samples. Therefore, there exists no reason to exclude biomass from cofiring applications on the basis of fly ash performance in concrete and the related standards should be revised.

Yes / This paper examines the impacts of clay mineralogy on the effectiveness of lime stabilisation at different temperatures. A comprehensive experimental programme was conducted to track down the evolution of lime-clay reactions and their durations through monitoring the evolution of strength gain at predetermined times using the Unconfined Compressive Strength (UCS) test. The study examined clays with different mineralogy compositions comprising Na+ Bentonite and Ball (Kaolinite) clay. Four different clays were tested including 100% bentonite, 100% Ball clay and two clay mixtures with ratios of 1:1 and 1:3 by mass of bentonite to Ball clay. All clays were treated using a range of lime content up to 25% and cured for a period of time up to 672 h at two different temperatures of 20 and 40 °C. The results showed that the continuity of the fast phase (stage 1) of strength gain was dependent on the availability of lime in particular at the higher temperature. Whereas, for the same lime content, the duration of the fast phase and the kinetic of strength gain were significantly related to the clay mineralogy and curing temperature. Except for the initial strength gain at 0 h curing time, the lime-treated Ball clay specimens at 20 °C appeared to show no strength gain throughout the curing period that extended up to 672 h. However, when curing occurred at 40 °C, the no strength gain stage only lasted for 72 h after which a gradual increase in the strength was observed over the remaining curing period of time. The addition of Bentonite to Ball clay succeeded in kicking off the strength gain after a short period of curing time at both curing temperatures.

Yes / Construction and demolition waste (CDW) management and recycling practices are crucial for transitioning to a circular economy. This study focuses on the detailed characterization of CDWs, including hollow brick (HB), red clay brick (RCB), roof tile (RT), concrete (C), and glass (G), collected from seven different sites. The CDWs were characterized based on particle size distribution, chemical composition, and crystalline nature. Pozzolanic activity was evaluated through compressive strength measurements of cement mortars with 20% cement replacement by CDWs at 7, 28, and 90 days. The results showed that clayey CDWs exhibited similar physical/chemical properties and crystalline structures. Compositions of Cs varied significantly based on their original materials. CDWs satisfied the minimum strength activity index for supplementary cementitious materials, with pozzolanic activity influenced by fineness and SiO2+Al2O3 contents. The average strength activity indexes for HB, RCB, RT, C, and G were 84.5%, 86.3%, 83.4%, 80.7%, and 75.8%, respectively. Clayey CDWs contributed to mechanical strength development, while Cs' contribution was related to hydration of unreacted cementitious particles. G exhibited the weakest pozzolanic activity due to its coarser particle size. Overall, CDWs demonstrated suitable properties for use as supplementary cementitious materials in PC-based systems.

Yes / This study aims to provide a thorough evaluation for the changes in the microstructure and evolution of strength of highly reactive clays that were treated with 7 % lime over a period of curing time as a function of the mixing moisture content. Three series of testing were carried out on specimens with 100 %, 85 % and 75 % of bentonite content and prepared with different moisture content of 10, 20, 30 and 40 % above the corresponding optimum moisture content. Specimens of 100 % bentonite were treated with 7 % of lime, compacted to achieve a predetermined dry unit weight and cured at temperatures of 20 OC and 40 OC for up to 28 days whereas the specimens with 85 % and 75 % of bentonite content were prepared by the addition of sand and were cured at 20 oC for up to 7 days. Unconfined Compressive Strength tests and Scanning Electron Microscopy were conducted to observe the strength and the microstructural changes resulting from increasing mixing moisture content. California Bearing Ratio and Resilient Modulus were correspondingly determined based on correlations with the Unconfined Compressive Strength. The failure pattern was also studied to better understand the ultimate behaviour of lime stabilised clays. The results revealed that the strength of treated bentonite increased with the increase in the moisture content up to 30 % above the corresponding optimum moisture content and with increasing the curing time and temperature. Nevertheless, substituting bentonite with sand on the specimen resulted in a significant reduction on the attained strength. Furthermore, the results of California Bearing Ratio and Resilient Modulus showed that values for both parameters are significantly enhanced with lime treatment. The microstructural analysis provided visual evidence to the improved strength in which the pozzolanic reaction was found to be significantly affected by the amount of moisture in the mixture. The results suggested that compacting lime treated expansive clays with moisture content moderately higher than the optimum moisture content would result in a significant enhancement to the attained strength over the period of curing.

Yes / Over the past two decades, extensive research has been conducted to explore alternative supplementary cementitious materials (SCMs) in order to address the environmental concerns associated with the cement industry. Bricks, which are frequently preferred in the construction sector, generate a lot of waste during the production and demolition of existing buildings, requiring environmentally sustainable recycling practices. Therefore, many studies have been carried out in recent years on the use of brick waste as supplementary cementitious materials (SCMs) in cement mortar and concrete production. This critical review evaluates the impact of waste brick powder (WBP) on the mechanical and durability properties of mortar and concrete when used as a partial replacement for cement. It was observed that the properties of WBP-blended cement mortar or concrete depend on several factors, including WBP particle size, replacement ratio, pozzolanic activity, and mineralogical structure. The findings indicate that WBP with a particle size range of 100 µm to 25 µm, with a maximum cement replacement level of 10–20%, exhibits a positive impact on the compressive strength of both mortars and concretes. However, it is crucial to emphasize that a minimum curing duration of 28 days is imperative to facilitate the development of a pozzolanic reaction. This temporal requirement plays a vital role in realizing the optimal benefits of utilizing waste brick powder as a supplementary cementitious material in mortars and concretes.