DSpace Coleção:
https://repositorio.ufba.br/handle/ri/22486
2024-03-28T12:44:06ZCimentos álcali-ativados preparados com resíduos de cimento-amianto inertizados
https://repositorio.ufba.br/handle/ri/39203
Título: Cimentos álcali-ativados preparados com resíduos de cimento-amianto inertizados
Autor(es): Carneiro, Gessivaldo Oliveira
Primeiro Orientador: Dias, Cleber Marcos Ribeiro
Abstract: The recycling of secondary raw materials, such as asbestos-cement waste (ACW) has
become a priority due to its carcinogenic potential. Thus, the search for technologies
that make the reuse of ACWs feasible is seen as a way to minimize environmental
impacts and disease risks. In this sense, methods were developed to allow the ACW
inertization, with emphasis on heat treatments, which are the most used. However,
there is a lack of studies aimed at optimizing this procedure, since it is an expensive
task. Thus, this work proposes to define the optimal parameters of ACW heat treatment
to simultaneously inertize chrysotile and embryonicly, to evaluate the application of
ACW treated as a precursor to the production of alkali-activated cement (CAA) of a
part. For the thermal treatment of the ACW, the optimization was performed by
applying a 2k
factorial design with a central point having as factors the temperature
(600 °C and 800 °C), the calcination time (1 and 3 h) and the mass of ACW (1 and 5
kg), considering minimum and maximum levels. Eleven experiments were used to
elaborate models that relate the answers: calcite content (% calcite), chrysotile content
(% chrysotile), belite content (% C2S) obtained through thermogravimetric analysis
(TG) and X-ray diffraction. (XRD). Simultaneous optimization was used to identify the
optimal levels of the factors for complete chrysotile dehydroxylation, to minimize
energy expenditure and CO2 emissions, and to maximize the content of belita (C2S) in
the treated ACW. Then, the treated ACW (ACWT) was used as a precursor to the
production of CAA of a part. The mixtures were prepared using ACWT, solid sodium
metasilicate (MSS) (SiO2 / Na2O equal to 0.98) and water. Eleven formulations
established using the I-Optimal design, served as basic formulations for the statistical
design of the mixture. The formulations established in the statistical planning were
characterized in terms of physical-mechanical properties, thermal and mineralogical
analysis. The results of heat treatment show the complete dehydroxylation of
chrysotile, with an increase in the content of belita (C2S) and CO2 emission, for
temperatures equal to or higher than 700 °C. It was observed that the optimal
conditions for the treatment were 5 kg of ACW, 800 °C, for 1 h. Using these
parameters, the chrysotile was completely eliminated, and the treated waste showed
40.42% of belite, which gives the material the agglomerating capacity, with an
estimated CO2 emission of 175.6 gCO2/kg of treated waste. In the dosage of alkaliactivated pastes, formulations with an MSS concentration of around 5% and molarities
close to 1M, showed the best mechanical properties. The addition of MSS had a strong
influence on the accumulated heat rate, which may be associated with the speed of
dissolution of the Si - O and Al - O bonds. The activated formulations showed superior
mechanical behavior in relation to the mixtures without activator. Furthermore, pastes
without activator have less shrinkage due to drying and chemical shrinkage. It was
found that the ACWT can be applied to the production of CAA and the statistical design
of the mixture is an efficient method in the prediction of the evaluated properties
Editora / Evento / Instituição: Universidade Federal da Bahia
Tipo: Dissertação2021-03-30T00:00:00ZUso dos elementos finitos e discretos na modelagem do comportamento drenado de uma areia aluvionar: um estudo comparativo.
https://repositorio.ufba.br/handle/ri/39153
Título: Uso dos elementos finitos e discretos na modelagem do comportamento drenado de uma areia aluvionar: um estudo comparativo.
Autor(es): Santos, Michelle Dias
Primeiro Orientador: Bandeira, Alex Alves
Abstract: For stress-strain analysis of geotechnical problems, several software programs are usually used, with their various constitutive models, most of them based on the finite element method (FEM), considering the soil as a continuous medium. However, it is known that soils are formed by particles and when a stress is applied, this stress is transmitted particle by particle and consequently, when subjected to external loads, they present a complex behavior, which can be better visualized at the micro scale. Thus, the use of the discrete element method (DEM) can be an alternative to predict soil behavior in a broader and more realistic way. However, because it is a relatively new method, its implementation and performance evaluation should be compared to classical methods, which are already well established and present adequate results. Knowing this, the present work aims to determine the drained behavior of an alluvial sand, through experimental studies and numerical simulation of triaxial tests. The numerical modeling was done employing the finite element method, using the software Sigma/W and OPTUM G2 and through the discrete elements, in the C programming language. Through the results obtained, a comparative analysis was performed and a discussion of the advantages and limitations of each method in representing the behavior of soils when subjected to triaxial tests. In general, it was found that the samples tested through the numerical methods presented results similar to those observed in the laboratory, within their limitations. In the case of DEM, there is the high computational cost and for FEM, the constitutive models available in the commercial programs used.
Editora / Evento / Instituição: Universidade Federal da Bahia
Tipo: Dissertação2022-11-18T00:00:00ZAvaliação da qualidade de dados altimétricos “alos world 3D – 30 m”
https://repositorio.ufba.br/handle/ri/39093
Título: Avaliação da qualidade de dados altimétricos “alos world 3D – 30 m”
Autor(es): Fagundes, Wendell Santana
Primeiro Orientador: Alixandrini Júnior, Mauro José
Abstract: Digital Elevation Models (DEM) at a global level are sources of data for several disciplines of
knowledge, implying a growing search for the best global models in terms of accuracy. Thus,
the present study had as its main objective to evaluate the altimetric quality and propose
corrections at a national level for the global MDE Alos World 3D – 30m (AW3D30), also
evaluating correlations of the vertical errors of the AW3D30 with land use and land cover
classes, derived from of the MapBiomas project, and applying corrections based on these
correlations. Finally, it validated the correction method by framing the PEC-PCD in the
original and corrected MDE. The materials of this study consisted of altimetric data that
represent the field truth, the MDE AW3D30 and Raster of land use and land cover from the
MapBiomas Platform. The methodology was structured starting with the acquisition,
treatment and normalization of the aforementioned data, then errors were estimated in the
MDE AW3D30 against field truth data, then statistical studies evaluated the consistency of
the data and the altimetric quality of the AW3D30 by MapBiomas class . In the sequence, the
work established parameters of altimetric correction using an empirical modeling, this model
was applied and validated in different regions. Given the exposed methodology, this study
was able to build corrected AW3D30 models for three validation areas, in the states of
Pernambuco, São Paulo and Bahia. The results showed a significant improvement in
altimetric accuracy, measured by the RMSE, whose values increased from 8.22m, 4.06m and
1.87m before correction to 4.55m, 2.48m and 1.26m after correction, respectively. The results
encourage the application of the corrective methodology proposed in this study throughout the
national territory, since it reduced the RMSE of the AW3D30 by 38.70%, on average, for the
validation areas.
Editora / Evento / Instituição: UNIVERSIDADE FEDERAL DA BAHIA
Tipo: Dissertação2023-07-10T00:00:00ZEstratégias TOD e os instrumentos do estatuto da cidade: avaliação da relação transporte e uso do solo no entorno das estações metroviárias da Região Metropolitana de Salvador
https://repositorio.ufba.br/handle/ri/38745
Título: Estratégias TOD e os instrumentos do estatuto da cidade: avaliação da relação transporte e uso do solo no entorno das estações metroviárias da Região Metropolitana de Salvador
Autor(es): Barbosa, Liniker de Jesus
Primeiro Orientador: Delgado, Juan Pedro Moreno
Abstract: Transit Oriented Development - TOD, translated as Public Transport Oriented Development can be defined as the development that occurs in the area of influence of a high capacity public transport system where there is an urban design, varied land use and an adequate density, covering non-motorized modes. Linked to this, Brazil has urban legislation with the objective to be developed with urban development in cities so the full well being that. In this, the City Statute (EC) was born, with great potential for urban transformation through its instruments, which are used in a precarious or even mistaken way. From this point of view, the aim of this research is to identify and evaluate transport-oriented development strategies considering the potential maintained in the various mobility instruments, aiming at promoting patterns of land use and occupation, as well as urban mobility occupied here, in the area of influence of the metropolitan stations of the Metropolitan Region of Salvador. The methodology takes into account the two dimensions that support this investigation (Mobility and Microaccessibility), translated into specificity, which are correlated to the TOD approach to be applied in this research. Each will provide technical steps between devices for the elaboration of integrated TOD urban implementation strategies by means of the identification of the localities where to densify and/or diversify the soil, depending on the application of the EC instruments, the Mobility Management Law and the Instrument of TUL urbanization. Finally, the results obtained can support public policies for integrated mobility and urban development.
Editora / Evento / Instituição: UNIVERSIDADE FEDERAL DA BAHIA
Tipo: Dissertação2022-06-27T00:00:00Z