https://repositorio.ufu.br/handle/123456789/19022 2026-07-28T07:22:22Z https://repositorio.ufu.br/handle/123456789/48855 Title: Uso combinado de fibras de PVA e PP em matriz com fíler calcário e metacaulim: efeito nas propriedades de compósitos cimentícios engenheirados Abstract: Engineered Cementitious Composites (ECC) are fiber-reinforced materials characterized by high ductility and strain-hardening behavior. The typical formulation of these composites employs fly ash as a partial cement replacement and 2% polyvinyl alcohol (PVA) fibers. However, the irregular availability of fly ash in some regions, combined with the high cost of PVA fibers, has driven the search for more viable and sustainable alternatives. In this context, this work aimed to investigate the impact of fully replacing fly ash with a combination of metakaolin and limestone filler in the ECC matrix, as well as to evaluate the effect of hybridizing PVA and polypropylene (PP) fibers on the composite's properties. The experimental program was developed in two stages: (1) formulation of matrices with full replacement of fly ash by metakaolin and limestone filler in proportions (1M1C and 1M2C), determining the superplasticizer content by mini-slump test; and (2) study of the hybridization of PVA and PP fibers at volumetric substitution levels of 0%, 25%, 50%, 75%, and 100% in two distinct matrices. The results showed that the matrix containing metakaolin and limestone filler (1M2C) exhibited workability and mechanical strength similar to the reference matrix (M45), making it a viable alternative. Fiber hybridization significantly affected the composite's behavior. The mixture with 1.5% PVA and 0.5% PP (1.5A_0.5P) offered the best balance between strength and ductility. Increasing the PP content reduced workability and flexural strength but increased deformation capacity. Microstructural analysis confirmed distinct failure mechanisms: rupture of PVA fibers and pull-out of PP fibers. The combined use of metakaolin and limestone filler proved viable for replacing fly ash in ECC production. Fiber hybridization allows the adjustment of ECC properties to meet specific application requirements. 2026-02-05T00:00:00Z https://repositorio.ufu.br/handle/123456789/48449 Title: Análise experimental de blocos sobre duas estacas metálicas com armadura metálica e não-metálica de barras de polímeros reforçada com fibra de vidro (GFRP) Abstract: Pile caps are fundamental structural elements in deep foundation systems, responsible for transferring loads from the superstructure to the piles. Due to their typical exposure to aggressive environments, such as high moisture conditions, these elements are prone to deterioration associated with steel reinforcement corrosion, which motivates the investigation of more durable reinforcement alternatives. In this context, this study experimentally evaluated the structural behavior of rigid pile caps supported by two steel piles, designed according to the strut-and-tie method, comparing models reinforced with CA-50 steel bars and glass fiber-reinforced polymer (GFRP) bars. All models were designed with identical geometry, loading conditions, and concrete strength, varying only the type and distribution of the main tensile reinforcement. The experimental program included material characterization tests, load tests up to failure, and detailed instrumentation to monitor strains, displacements, crack development, and load distribution at the supports. The results showed that steel-reinforced pile caps exhibited behavior consistent with rigid block assumptions, presenting lower deformations and better crack control. Conversely, GFRP-reinforced pile caps showed larger deformations and crack widths, indicating a more flexible structural response, even when designed using the same criteria. It was also observed that distributing the GFRP reinforcement along the entire length of the tie resulted in improved structural performance compared to concentrating the reinforcement only in the anchorage region. The study concludes that the use of GFRP bars in pile caps is structurally feasible in terms of ultimate strength; however, additional design criteria related to deformation and crack control are required. 2026-02-06T00:00:00Z https://repositorio.ufu.br/handle/123456789/48019 Title: Estudo do coagulante tanfloc e do coagulante sulfato de alumínio no tratamento de efluente de laticínio Abstract: The increase in demand for water and the need for adequate treatment of industrial effluents have encouraged the search for more efficient and sustainable processes. In the dairy industry, which generates effluents with high organic load, color, and turbidity, coagulation and flocculation are essential steps for the removal of particles and organic matter, and the choice of coagulant is decisive for the performance of the treatment. In this context, this study compared the chemical coagulant aluminum sulfate to the natural coagulant Tanfloc in the removal of color and turbidity from dairy effluent, through tests in Jartest equipment and the preparation of coagulation diagrams to define the ideal pH and dosages, complemented by digital image analysis to evaluate the characteristics of the flocs formed and sedimentation behavior. The results indicated that aluminum sulfate showed good removal, but required strict pH correction and higher dosages, implying an increase in input consumption and the production of sludge with a higher metal content. Tanfloc, on the other hand, showed efficiency in wider pH ranges and at lower dosages, in addition to generating less sludge, with biodegradable characteristics. Although Tanfloc has a higher unit cost, its application can reduce indirect operating costs and environmental impacts. It can be concluded that Tanfloc is a promising and sustainable alternative to aluminum sulfate, especially in systems that seek efficiency combined with waste reduction and operational simplification. 2025-12-12T00:00:00Z https://repositorio.ufu.br/handle/123456789/47909 Title: Efeito de aditivos superplastificantes em argamassas de revestimento com fíler calcário e incorporadores de ar Abstract: The use of superplasticizers can influence the properties of mortars in both the fresh and hardened states, as well as the tensile bond strength when applied to a substrate. This study aims to evaluate the effect of different superplasticizing admixtures on the applicability of rendering mortars. Four base compositions were evaluated: (i) cement (C10), (ii) 30% cement replacement by limestone filler (C40), (iii) an air-entraining admixture (IA), and (iv) a plasticizing and stabilizing admixture (PE); each was tested both without and with the addition of one of three superplasticizers: a lignosulfonate-based (A) and two polycarboxylate ether based types (B and C). The investigation was conducted in three stages: (1) on pastes to evaluate the influence of superplasticizers on hydration kinetics via isothermal calorimetry; (2) on mortars to determine their impact on fresh and hardened properties; and (3) on mortar applicability to evaluate how the admixtures affect rendering application procedures and the properties of the mortar–substrate system. In the first phase, sixteen pastes mixtures with a water–binder ratio of 0.50 were tested. For the mortar phase, a 1:4 (cement: sand) volumetric mix proportion was used as the reference. Fresh mortar properties evaluated included bulk density, entrained air content, and water retention capacity. At 28 days, hardened properties was assessed, including flexural tensile strength, compressive strength, dynamic modulus of elasticity, and capillary water absorption. In the third phase, selected mortars were applied by a professional workmanship onto ceramic brick panels and subsequently tested for fresh and hardened state properties, as well as tensile bond strength tests. The results indicated that the superplasticizer admixtures influenced the hydration kinetics of the pastes, increasing the dormant period and thereby retarding hydration; this retarding effect was most pronounced for the lignosulfonate-based admixture (A). In the mortar study, admixture A yielded lower mechanical strength compared to the polycarboxylate-based admixtures (B and C). Conversely, superplasticizers B and C increased flexural tensile strength. The use of superplasticizers delayed the the setting time in all pastes mixtures.In mortars, the use of superplasticizers improved performance in both fresh and hardened states and increased the tensile bond strength. 2025-11-18T00:00:00Z