RESUMO Em algumas construções são necessárias intervenções para restabelecer ou aumentar a capacidade de suporte da estrutura antes de atingir um estado limite. Os Polímeros Reforçados com Fibra de Carbono (CFRP) são um dos mais adequados como elemento de reforço estrutural por ser um material de alto desempenho mecânico e elevado módulo de elasticidade, resistência à fadiga e baixo peso específico. Este trabalho teve como objetivo analisar a eficiência de materiais compósitos de Polímeros Reforçados com Fibras de Carbono (CFRP) como reforço estrutural em vigas de concreto armado, por meio de ensaios experimentais e simulação numérica. Nos ensaios, a armadura da viga de concreto foi dimensionada com resistência insuficiente ao cisalhamento. Nas vigas de referência, inicialmente, surgiram fissuras de cisalhamento, e em seguida as vigas romperam-se à flexão. Nas vigas com CRFP, que foram dimensionadas como reforço ao cisalhamento, as vigas não apresentaram fissuras de cisalhamento e romperam à flexão. Não houve acréscimo significativo da carga máxima. Em apenas uma viga houve o descolamento da fibra de carbono em um dos bordos da estrutura, mostrando boa eficiência do adesivo utilizado. As simulações numéricas foram realizadas utilizando o Método dos Elementos Finitos (MEF) no software ANSYS 18.1. Os resultados obtidos no modelo numérico ficaram próximos aos resultados experimentais.

This paper presents a study with concretes produced with natural aggregates, recycled concrete aggregates (RCA) and waste porcelain aggregates (WPA). The study analyzed the influence of recycled aggregates in the mechanical properties of conventional concretes and evaluated the difference between measured and predicted values of elasticity modulus. The incorporation of WPA in concrete showed better mechanical results compared to the concretes produced with RCA. Measured elasticity moduli were lower than moduli predicted by NBR 6118:2014 and fib Model Code 2010, while measured results were greater than values predicted by Eurocode 2:2004 and ACI 318:2014, as expected, which indicated the safety of the latter two standards.

The use of synthetic materials with high corrosion resistance in a concrete matrix yields structures that are more durable and suitable for use in aggressive environments, eliminating the need for frequent maintenance. Examples of such materials include glass (GFRP) and basalt (BFRP) fiber-reinforced polymer bars (FRP). Due to the low modulus of elasticity of these bars, concrete elements reinforced with FRP longitudinal rebars tend to exhibit cracks with wider openings and greater depths compared to those reinforced with steel rebars, which diminishes the element’s shear resistance. The addition of discontinuous fibers into the concrete aims to maintain stress transfer across the cracks, thereby enhancing the shear capacity and ductility of FRP-reinforced structures. This study evaluates the impact of fiber addition on the shear resistance of concrete beams reinforced with FRP rebars. An experimental investigation was conducted, focusing on the partial and complete substitution of stirrups with polypropylene macro fibers in concrete beams reinforced with FRP longitudinal rebars and stirrups. This research examined beams reinforced with glass (GFRP) and basalt (BFRP) fiber-reinforced polymer bars. For the initial set of beams, all stirrups were replaced with synthetic macro fibers. In the subsequent set, macro fibers were added to beams with insufficient stirrups. Although the complete replacement of GFRP and BFRP stirrups with polypropylene macro fibers did not alter the brittle shear failure mode, it did enhance the shear resistance capacity by 78.5% for GFRP-reinforced beams and 60.4% for BFRP-reinforced beams. Furthermore, the addition of macro fibers to beams with insufficient stirrups, characterized by excessive spacing, changed the failure mode from brittle shear to pseudo-ductile flexural failure due to concrete crushing. In such instances, the failure load increased by 18.8% for beams with GFRP bars and 22.8% for beams with BFRP bars.

Concern to the environment, due to the large amount of construction waste that is improperly disposed, encouraged the processing of these with the intention of returning them to the productive system. Studies to intensify the reuse of construction waste have intensified recently, developing standards for the production, evaluation and use of recycled aggregates, for which consumption is still incipient. For the development of the work, the characteristics of the recycled and natural aggregates were determined, including fine content. Two types of mortars were developed, one hydraulic and the other mixed. The recycled aggregate was used to replace the natural aggregate, in the proportions of 30% and 60%, for both types of mortar. The characteristics of the mortars in the fresh and hardened states were determined and the mortars were classified according to the specification standard for laying and coating mortars. The correlation between the fines contents of the mortar and the characteristics in the plastic and hardened states was verified for most of the observed characteristics. In the plastic state, the increase in the percentage of substitution of natural aggregate by the recycled produced a specific mass reduction of the order of 4% for both types of mortar, and the water retention capacity presented an inverse behavior, mixed mortars presented better results in this aspect. In the hardened state, the tensile and compressive strengths had lower results due to the increase in the substitution of the natural aggregate by recycling. The hydraulic mortar presented better performance than the mixed mortar when classified according to NBR13281.