https://repositorio.ufba.br/handle/ri/22485 Sun, 17 May 2026 11:37:46 GMT 2026-05-17T11:37:46Z https://repositorio.ufba.br/handle/ri/44305 Durabilidade química e biológica de fibras vegetais tratadas com nanopartículas de prata para uso como reforço de matrizes cimentícias. Alves da Silva Neto, Gilberto Lopes Lima, Paulo Roberto Vegetal fibers have a low affinity to the high alkalinity of Portland cement matrices, in addition to presenting high dimensional instability in the presence of moisture. Besides, lignocellulosic fibers are subject to fungal biodeterioration, mainly during storage. Thus, treatments on the fibers and matrices are required to have a durable composite. Therefore, this work aims to propose a thermochemical treatment that generates fibers impregnated with silver nanoparticles (AgNP) to verify their influence on dimensional instability and fiber-matrix interaction, in addition to their chemical and biological durability. After treatment, the jute and sisal fibers were evaluated for their physical, thermal, morphological, and mechanical properties. The proposed AgNP impregnation method was satisfactory, with efficiency dependent on the AgNP concentration and fiber species. A change in the surface texture of the fibers was observed, becoming rougher, with better dimensional stability and reduced water absorption capacity of the modified fibers. It is believed that not only thermal cycles but also the low pH of the AgNP solution altered the microstructure of the fibers. The fibers treated in aqueous AgNP solution did not show significant changes in tensile strength or Young's modulus compared to natural fibers. Regarding fiber-matrix adhesion, evaluated by the pull-out jhtest, better performance was observed for hornificated fibers, due to the morphological modification of the surface; however, the adhesion strength of these fibers after treatment with AgNP did not show significant modification. When subjecting these fibers to alkaline attack, changes were observed in the thermograms with removal of hemicellulose, surface damage with defibrillation and, consequently, reduction in the mechanical performance of the tensile strength of these fibers, regardless of the treatment applied. On the other hand, when subjecting the fibers to fungal attack by direct contact, a superior performance of the fibers treated with AgNP was noted, evidenced by the little altered thermograms, absence of damage in the morphology, and maintenance of the tensile strength and Young's modulus. Thus, in general, the treatment of plant fibers with AgNP proved to be satisfactory for application in cementitious composites. UNIVERSIDADE FEDERAL DA BAHIA Tese Tue, 03 Jun 2025 00:00:00 GMT https://repositorio.ufba.br/handle/ri/44305 2025-06-03T00:00:00Z https://repositorio.ufba.br/handle/ri/44283 Modelo para gerenciamento do processo de digitalização do licenciamento de obras na etapa de concessão dos alvarás para construção em municípios brasileiros Brito, Douglas Malheiro de Costa, Dayana Bastos Municipalities around the world are seeking to digitalize the building permit process, especially the construction permit stage, to reduce processing times and increase the efficiency and automation of code checks. There is a growing interest in studies that develop tools that enable a greater understanding of how municipalities can gradually advance through the digitalization stages. However, the literature has indicated that these studies need to consider organizational and procedural aspects of digitalization, in addition to the technological aspect, allowing for an understanding, management, and control of a gradual transition from traditional processes. The objective of this study is to propose a model for managing the planning, implementation, and monitoring of the digitization process for building permits in medium-sized to large Brazilian municipalities. The research strategy adopted was Design Science Research (DSR), involving a longitudinal case study in the Brazilian municipality of Salvador, the conducting of two surveys, and the identification of pioneering digitalization initiatives in 22 countries to propose the model. The evaluation included conducting simulations of twelve possible digitalization scenarios and applying the model to the municipality of Belo Horizonte. The results obtained comprise a management model with an evolutionary roadmap, considering eight factors influencing the digitalization process, seven metrics for estimating and monitoring performance, as well as recommendations for implementation and supporting artifacts, according to the context, extension, and level of digitalization and automation intended by the municipality. The main theoretical contribution is associated with the model’s multiplicity of functions, whether through the representation of the planning, sequencing, implementation, monitoring, updating of municipal legislation and restarting of digitalization stages, or the managerial character of supporting decision-making by municipalities through its potential to sequence digitalization, simulate scenarios, estimate performance and evaluate the progress of maturity until the achievement of the intended levels of digitalization and automation.. As a practical contribution, the operationalization of the model in an application tool, along with documents containing recommendations and best practices, can assist municipalities in developing implementation strategies. Furthermore, the proposed metrics can guide decision-making by the professionals involved, from the initial planning and sequencing stages to monitoring performance and the benefits achieved. Universidade Federal da Bahia Tese Fri, 12 Dec 2025 00:00:00 GMT https://repositorio.ufba.br/handle/ri/44283 2025-12-12T00:00:00Z https://repositorio.ufba.br/handle/ri/43131 Avaliação do efeito da camada de oxalato de zinco na resistência à corrosão do aço galvanizado em concreto armado via técnicas eletroquímicas Barretto, Tatiana Conceição Machado Ribeiro, Daniel Véras The corrosion of reinforced concrete steel bars significantly reduces the service life of struc-tures and can be accelerated in aggressive environments, such as chloride-rich atmos-pheres, where pitting corrosion may occur. Among the protection methods for reinforcing steel against corrosive processes, galvanization has proven to be an effective alternative, especially when combined with surface treatments such as hexavalent chromium (Cr⁶⁺ or Cr VI) solutions. However, several studies indicate that Cr VI is toxic and carcinogenic, mak-ing it necessary to develop alternative coatings. This study addresses a significant gap in the literature by focusing on the behavior of oxalic acid-treated galvanized steel in alkaline solutions (pH > 7), specifically for civil construction applications. In this context, dicarboxylic organic acid-based solutions have gained attention for providing effective corrosion protec-tion while being less toxic and more cost-effective compared to conventional treatments. This doctoral research aimed to evaluate the corrosion resistance performance of zinc oxa-late coatings applied to reinforcing steel in alkaline environments. For this purpose, galva-nized steel samples were subjected to a conversion treatment in oxalic acid solution (0.1 M), then exposed to an alkaline medium simulating the pore solution of concrete C30 class. The samples were also embedded in concrete specimens and monitored over controlled time intervals. The investigation combined morphological (SEM/EDS) and point chemical, mineralogical (XRD), and spectroscopic (FTIR) analyses with electrochemical tests, includ-ing polarization resistance and electrochemical impedance spectroscopy (EIS), on samples subjected to salt spray exposure to assess the evolution of the zinc oxalate layer and its influence on corrosion resistance. The results demonstrated that the formed layer exhibited an average thickness of 10 μm, delaying the onset of corrosion at the initial stages. However, over longer exposure periods, the alkalinity of the medium and the porosity of the concrete promoted coating degradation, this was observed in both the alkaline solution and the con-crete. Comparatively, treated samples showed an initial corrosion current density (Icorr ≈ 4.7 × 10⁻⁴ mm/year) similar to untreated samples (≈ 5.3 × 10⁻⁴ mm/year), while impedance spectroscopy indicated a charge transfer resistance (Rct) of up to 497 Ω after three months, decreasing to approximately 207 Ω after twelve months. Corrosion rates exceeded 0.1 mm/year in the treated samples, which, according to normative criteria, represents a severe corrosion grade. Therefore, it is concluded that zinc oxalate delays corrosion initiation; how-ever, its stability in alkaline media is limited, compromising the long-term effectiveness of the coating under prolonged exposure. Universidade Federal da Bahia Tese Wed, 01 Jan 2025 00:00:00 GMT https://repositorio.ufba.br/handle/ri/43131 2025-01-01T00:00:00Z https://repositorio.ufba.br/handle/ri/43016 Cavilha de madeira reforçada com fibras de vidro como conector em seções mistas de madeira e concreto Santos, Filipe Luigi Dantas Lima César, Sandro Fábio Considering the global trend to reduce the environmental impact caused by the construction industry, timber-based projects have increasingly emerged as an appropriate response to lowering the carbon footprint and embodied energy of building materials. This study proposes a connection system composed of hardwood dowels reinforced with glass fibers in an epoxy matrix (GFRP) as an alternative to metallic connectors in timber–concrete composite (TCC) structures. To achieve this objective, the research was divided into three stages: characterization of raw materials (timber, concrete, glass fibers, and GFRP), characterization of GFRP-reinforced dowels in terms of physical and mechanical properties (water absorption, bending strength, axial compression, embedment, and pull-out), and evaluation of connection systems in timber–concrete composite specimens through push-out tests. The push-out tests considered dowel diameter, reinforcement, and insertion angle into the timber as variables, resulting in eight experimental series. The results showed that GFRP reinforcement reduced the average water absorption rate by 85%, increased bending strength by 84%, and compression strength by 46%. Regarding pull-out, the behavior was limited by the low slenderness ratio, while embedment tests indicated that fiber orientation had no influence on strength, but affected post-failure behavior. Push-out tests confirmed the influence of orientation, diameter, and GFRP reinforcement on connection stiffness. For perpendicular dowels without reinforcement, increasing the diameter from 16 mm to 20 mm resulted in stiffness gains of 91% and 27% in the service slip modulus, respectively. With GFRP reinforcement, stiffness increased by approximately 35% to 104% in parallel and inclined series, respectively. When comparing orientations, inclined dowels exhibited up to 51% greater stiffness than perpendicular ones. Overall, the findings indicate that GFRP reinforcement enables composite action efficiencies comparable to those of metallic connectors, confirming its potential as a sustainable alternative for timber–concrete composite systems. Universidade Federal da Bahia Tese Thu, 04 Sep 2025 00:00:00 GMT https://repositorio.ufba.br/handle/ri/43016 2025-09-04T00:00:00Z